JP2023000957A - Handpiece tip position and orientation detection device, handpiece guidance system, and handpiece guidance assistance system - Google Patents

Abstract

To develop a magnetic field vector sensor grid using GSR sensors and install the same in a tip of a handpiece so as to enable detection of the position and orientation of a fine magnet, and to realize a guidance system for automatic detection.SOLUTION: Magnetic field vector sensors having a detection power of 10 nT or less and a magnetic field vector sensor grid are developed to measure a magnetic field generated by a magnet 72, and the position and orientation of the magnet is highly accurately detected by inputting the measurements into a Gauss-Newton method-based computation method after appropriately selecting an error in and the number of input datasets.SELECTED DRAWING: Figure 11

Description

The present invention attaches mini magnets to the teeth in the oral cavity, attaches a magnetic field vector sensor grid to the handpiece, measures the positional relationship between the handpiece and the magnet, and determines the position of the handpiece based on that. The present invention relates to a detection device and a guidance system for measuring azimuth with high precision and in real time.

In the field of dental implant treatment, there is an increasing need for the development of a system for highly accurate measurement of the position-orientation relationship between the implant-embedded hole and the handpiece and for guiding the handpiece.
A method for optically measuring the position-orientation relationship has been developed (Non-Patent Document 1), but the accuracy is poor and the handpiece cannot be directly guided in the oral cavity. Therefore, a complex indirect method, that is, by creating an intraoral model and using optical markers attached to the model and the mouthpiece, obtains position-orientation data of the handpiece and optical markers on the model. While performing treatment on the model, the guidance trajectory of the handpiece at that time is stored in the computer, and based on this data, the actual treatment is automatically controlled. Treatment is performed while correcting the relative positional relationship by measuring the positional relationship between the handpiece and the optical marker attached to the mouthpiece.

The magnetic type measures the position and orientation of the handpiece by attaching a magnetic marker to the teeth as a reference in the oral cavity and attaching a magnetic sensor grid that is fixed and installed on the patient's side. Although it is simple, it is very difficult to achieve excellent measurement accuracy because only a small magnetic marker with a width of 4 mm and a length of 8 mm can be used if the tooth size is the maximum size. Moreover, a magnetic field vector sensor capable of sensitively measuring minute magnetic fields emitted by external magnetic markers has not yet been developed. Only significantly inferior ones have been developed. In addition, the measurement speed of the existing developed product is as slow as 1 Hz, and significant improvement is required.

Japanese Patent Application Laid-Open No. 2002-200001 discloses a magnet type position/orientation calculation system. This consists of an NdFeB magnet (size: 0.8 mm × 2.5 mm, three magnets) with a magnetic moment of about 4.8 × 10 ^-9 Wbm, and an FG sensor with a magnetic field detection power of about 1 nT. A three-axis magnetic field sensor is used to enable measurement of the position of the magnetic marker. According to this disclosure, a method is provided in which the magnet side moves and traces the position of the magnet body marker with an externally fixed magnetic sensor. The magnetic markers attached to the handpiece and teeth mean that the handpiece and the patient themselves move, and the positions of the magnetic markers also move, so this disclosure cannot be used as it is.

Furthermore, the positional accuracy is about 4 mm, which is significantly inferior to the positional accuracy of 0.5 mm or less required for implant treatment. The main reason for this is thought to be that since no magnetic field vector sensor is used, there is a large deviation between the positions of the mutual measurement values of the three-axis magnetic field sensors. Although the three-axis magnetic sensor used (Patent Document 1, FIG. 2) is not accurately described in this document, assuming that the diameter of the magnetic field sensor is 3 mm to 5 mm, approximately each magnetic field sensor measures The positions are shifted from each other by about 1.5 mm to 2.5 mm, and it is believed that this mutual error causes a significant loss of the positional accuracy of the present disclosure.
Also, since this disclosure does not use a magnetic field vector sensor, it cannot be calculated according to the Gauss-Newton method. Therefore, an iterative process utilizing magnetic field gradients is performed to obtain X, Y, Z, Θ, and Φ that minimize the error between the measured and theoretical values. It seems that there is a problem with real-time performance. In fact, Patent Document 1 does not describe the measurement speed. As described above, the position of the magnetic marker cannot be measured with high accuracy in the present disclosure that does not presuppose the magnetic field vector sensor.

As a three-axis magnetic field sensor, there is an electronic compass (Patent Document 2) of Aichi Steel Co., Ltd., which uses an MI sensor. , the magnetic field measurement positions in the Z-axis direction are shifted by about 1 mm, and the magnetic field vector at a predetermined position cannot be measured. Also, the magnetic field detection power is as low as 200 nT. Even if this product is applied to the invention of Patent Document 1, improvement in the positional accuracy of the magnetic marker cannot be expected. In order to improve the positional accuracy, it is important to use a magnetic field vector sensor capable of pinpoint magnetic field vector measurement using a three-dimensional magnetic sensor instead of a three-axis magnetic field sensor for magnetic field measurement.

As a magnetic field vector sensor, there is an electronic compass (Patent Document 3) of Asahi Kasei Corporation as a magnetic field measuring device using a Hall sensor. It is a combination of four Hall elements and one permalloy magnetic collector, and the sensor element spacing is about 1 mm, and it is possible to measure the magnetic field vector at a pinpoint predetermined position. Although it is possible to fabricate a sensor grid arranged at a high density, there is a problem that the magnetic field detection capability is only about 10 mG (=1000 nT), and minute magnetic fields cannot be measured.

A magnetic field vector sensor using a GMR sensor is introduced in US Pat. It has a small size of 2 mm x 2 mm, a detection power of about 500 nT, and a problem that the measurement accuracy of Hx and Hy differs from that of Hz. As a result, there is a problem that a minute magnetic field cannot be measured.

As a magnetic field vector sensor using an FG sensor, there is an nT meter (Non-Patent Document 2) manufactured by MTI. Although the detection power is at the 1 nT level, the elements are attached to the six sides of a 30 mm cube, and the spacing between the sensor elements is about 30 mm. You will be measuring the gradient and cannot pinpoint the magnetic field measurement at a particular location. It is also larger than the size of the handpiece and cannot be attached to it.

As a type using a GSR sensor (Patent Document 5), there is an electronic compass (Patent Document 6) by Magnedesign. It is a combination of four GSR elements and a pair of permalloy magnetic collectors, and the sensor element spacing is about 0.5 mm. It is possible to measure the magnetic field vector at a pinpoint predetermined position, and the magnetic field detectability is also measured. It is 100nT or less at a speed of 200Hz, which is superior to Hall sensors and MI sensors. However, the required magnetic field detection power is insufficient when compared to 50 nT or less at a measurement speed of 1 KHz. If this product is applied to the invention of Patent Document 1, improvement in the positional accuracy of the magnetic marker can be expected. Moreover, since it is an iterative process method, the measurement speed must be less than 1 Hz.

In order to accurately and quickly measure the position and orientation of a small magnet placed on a detection object, it is necessary to develop a compact magnetic field vector sensor with high magnetic field detection capability. Specifically, there is a demand for the development of a magnetic field vector sensor that can detect a minute magnetic field of 50 nT or less at a measurement speed of 1 kHz and can measure the magnetic field vector at a pinpoint predetermined position in a minute space of 4 mm × 4 mm × 2 mm or less. ing.

Regarding the algorithm for calculating the position and orientation of the magnet, as a method of simultaneously obtaining the position and orientation of the magnet using the magnetic field vector sensor grid, an error function is defined in Non-Patent Document 3, and the coordinate components that minimize the error function A method for determining the three components of X, Y, and Z is described. However, it does not describe how to obtain .theta. and .phi., and does not describe how to obtain the three coordinate components X, Y and Z and the directions .theta. and .phi. from the error function. Note that the measurement position error in Non-Patent Document 3 is as large as 5.5 mm, which is not of a practical level. Strictly speaking, the magnetic field vector sensor described in this document has a deviation of 1.8 mm between the measurement positions of the three-axis sensor. It seems to be because Furthermore, the size of the sensor used is too large to be attached to the handpiece.

In developing a magnetic position and orientation measurement and guidance system for a dental handpiece, in order to improve the accuracy of the conventional magnetic positioning method, we developed a high-performance magnetic field vector sensor and installed a sensor grid on a small handpiece. It is necessary to develop a measurement system that can accurately measure the relative position and orientation of the handpiece and the magnetic body inside the oral cavity every moment, regardless of the movement of the handpiece and the magnetic body inside the oral cavity. In terms of performance, there is a demand for the development of a device that has a measurement speed of 1 Hz to 50 Hz, a position accuracy of 0.1 mm or less, and performance that is about 100 times that of conventional devices.

Japanese Patent Application Laid-Open No. 2001-524012 Japanese Patent No. 3781056 Japanese Patent Application Laid-Open No. 2004-61380 Japanese Patent Publication No. 2013-518273 Japanese Patent No. 6506466 Japanese Patent No. 6021239 Japanese Patent No. 6021239

Naotomo Kondo, Yutaro Oyamada: "Current status and future of robotic surgery in oral implant treatment", Journal of Japan Prosthodontics, 13-21, 2021 MTI Co., Ltd. Website Product Information FGS3-1000 Takashi Nagaoka, Akihiko Uchiyama: Tateishi Science and Technology Foundation Grant Research Report: No. 15, pp. 52-55 (2006) Y.Honkura, S.Honkura ; JMMM513(2020)167240

The present invention measures the position and azimuth relationship of the magnet by using a magnetic field sensor grid in which the magnet installed on the tooth is installed on the handpiece, and uses the measured values to determine the position of the tip of the handpiece and the oral cavity. It is to measure the relative position and azimuth relationship with the treatment position in the inside with high accuracy and realize a handpiece guidance system using it. For this purpose, we need to develop a technique for accurately measuring the position/orientation relationship between the magnet attached to the tooth and the tip of the handpiece.

According to the present invention, the magnet as the magnet marker is an AC electromagnet, a pulse electromagnet, or a permanent magnet with a width of 6 mm or less, a length of 10 mm or less, and a magnetic moment of 5×10 mm. ^-9 to 100 × 10 ^-9 Wbm, one magnet is placed on a specific tooth in the oral cavity, the magnetization vector is set in the horizontal direction (X axis), and the center of the magnet is the origin. Let the magnet coordinate system with the direction of the vector as the X axis, the thickness direction of the magnet as the Y axis, and the longitudinal direction as the Z axis be the Cm system,
The magnetic field vector sensor grid has at least five magnetic field vector sensors arranged in a grid on the grid attached to the handpiece. Let the coordinate system with the horizontal X-axis and the vertical direction of the grid as the Z-axis be the C system,
Position/azimuth detector for a handpiece that can measure the positional relationship and azimuth relationship between both coordinate systems at a measurement speed of 1 Hz to 50 Hz or less, with a position accuracy of 0.1 mm or less, and an azimuth accuracy of 1 degree or less. It is about.

As a technical development task for that purpose, the first task is to develop a magnetic field vector sensor having a detection power of 50 nT or less at a measurement speed of 1 KHz. A GSR sensor has been developed as a small sensor capable of detecting minute magnetic fields. The object is to devise a magnetic field vector sensor structure that can make the measurement error the same.

A second issue relates to the design of the magnet. The size of the magnet is so small that it can be attached to the teeth, and the positional accuracy is 0.1 mm or less and the azimuth accuracy is 1 degree or less even at a distance of 20 mm to 100 mm. need to make it possible. In addition, it is necessary to devise ways to avoid the effects of fluctuations in the surrounding magnetic field environment, especially fluctuations due to movement of the handpiece. Furthermore, it is necessary to devise a way to specify the magnet coordinate system Cm using one magnet placed on the tooth.

A third challenge is to design a geometrically designed magnetic field vector sensor grid on the handpiece. As the number of magnetic field vector sensors on the grid increases, the accuracy of position and azimuth calculations improves. Proper placement is important.

The fourth task is to devise a calculation program for calculating the position and orientation of the magnet with high precision and excellent real-time performance. With the magnetic field vector sensor grid, when the magnetic field vector emitted by the magnetic marker is measured as the magnetic field vector at each measurement point, no iterative process is required. A method of defining a function and calculating X, Y, Z and θ, φ from its minimum value is widely known as the Gauss-Newton method. Using this principle, we consider the magnet performance, sensor performance, the number and arrangement of sensors, the distance between the magnetic marker and the magnetic field vector sensor grid, and the shape and size of the target product on which the magnetic field vector sensor is placed on the grid. There is a difficulty that can not be said to be the selection of design parameters to devise a calculation program for .

The fifth problem is to obtain the relative positional relationship between the tip of the handpiece and the treatment position in the oral cavity using the magnetic field vector sensor grid, and to ensure that the tip of the handpiece is at a predetermined treatment position with a displacement of 0.5. The present invention relates to a guidance system capable of providing guidance such that the misorientation is 1 mm or less and the misorientation is 1 degree or less.

A sixth issue is countermeasures against movement of the patient during guidance of the handpiece.

The conventional method obtains the position and orientation of the moving magnet in a grid system fixed to the device (in other words, the coordinate system of the device), and the positional relationship between the device and the magnet can be grasped as it is. However, the subject of the present invention is the case where the orientation and position of the handpiece fluctuate, and the position and orientation of the magnet also slightly fluctuate according to the movement of the patient. In other words, both are active, and simply obtaining the relative position/orientation relationship between the two does not allow the operator of the handpiece or a mechanical control device such as a robot to grasp the position/orientation of the handpiece. information necessary for control cannot be obtained. It is necessary to devise a new algorithm for measuring the position and orientation of such a working grid system and magnets.

The present invention consists of a magnet, a magnetic field vector sensor, a magnetic field vector sensor grid, a sensor grid data processing circuit, a position/orientation calculation program, a data processing device incorporating it, and a handpiece guidance system.
Therefore, the present inventor first worked on the development of a magnetic field vector sensor having high detection power, which is the first problem.

As a magnetic field vector sensor using a GSR sensor, as disclosed in Patent Documents 6 and 7, it has a detection power of 100 nT or less at a measurement speed of 200 Hz, and its size is the size of an integrated circuit 1.4×1. Considering 4 mm, it is about 2×2 mm.

Here, the GSR sensor is described in detail in Patent Document 5, which is cited in the present invention. As shown in FIG. 1, the GSR sensor consists of a detection coil formed of a magnetic field detection magnetic wire having conductivity on a substrate, a circulating coil wound around the wire, two electrodes for wire conduction, and an electrode for detecting coil voltage. A means for applying a pulse current having a frequency of GHz to a GSR element composed of wiring connecting two electrodes and a magnetic wire, and a coil voltage generated when the pulse current is applied are detected, and the coil voltage is detected by an external magnetic field H It is an ultrasensitive micro magnetic sensor consisting of an electronic circuit (Fig. 2) that converts to

The present inventors have tried to increase the length of the GSR element, increase the number of coil turns, improve the shape of permalloy and the magnetic circuit to strengthen the magnetic gathering force of the magnetic field Hz in the Z-axis direction, and directly apply the magnetic field to the ASIC surface. By forming and connecting to the ASIC circuit with via holes for electrodes, the performance of the magnetic field vector sensor can be improved to 50 nT or less detection power at a measurement rate of 1 KHz without changing the sensor size. It was decided to use the sensor in the present invention. ASIC is an application specific integrated circuit.

This integrated magnetic field vector sensor will be described with reference to FIGS.
On the ASIC 31, the X1 element and the X2 element are symmetrically arranged in the X-axis direction with the origin as the center, and the Y1 element and the Y2 element are symmetrically arranged in the Y-axis direction orthogonal to the X-axis direction. Each element is coated on the upper surface of the ASIC, a magnetic wire 32 is arranged in a grooved resist layer, and a detection coil and four electrodes (33, 34) are formed around the magnetic wire 32. The four electrodes (33, 34) are connected with the ASIC through connecting electrode holes 38. FIG. One upper soft magnetic body 35 is formed above the magnetic wire 32 at the origin, and lower soft magnetic bodies 36 are formed below the magnetic wire 32 at the ends of the four elements opposite to the origin. ing.
With this configuration, the magnetic field in the X-axis direction and the Y-axis direction is detected, and the magnetic field in the Z-axis direction is collected 391 (or discharged) by the upper soft magnetic body 35. It is detected by being discharged (or collected) by 392 . Therefore, the magnetic field vector (Hx, Hy, Hz) at the origin is detected.

A GSR sensor is used to measure a magnetic field at a rate of 1 MHz to 5 MHz, average it, and output it at a measurement rate of 200 Hz to 500 KHz. The detection power of the GSR sensor increases in proportion to the length of the magnetic wire. In order to measure a minute magnetic field of 5 nT or less at a measurement speed of 1 kHz in a minute space range, the present inventor directly molded a GSR element with a long magnetic wire length of 1 to 2.4 mm on the surface of an ASIC to achieve a small size. An On-ASIC type GSR sensor (Non-Patent Document 4) was manufactured, and using it, an assembly type magnetic field vector sensor was developed and used in the present invention.

As shown in FIGS. 5 and 6, the assembly type magnetic field vector sensor consists of four On-ASIC type GSR sensors 41 (size: 2 mm long, 1 mm wide) attached to the ridge line 402 of the truncated square pyramid 40. It is affixed on four slopes in four-fold symmetry and mirror symmetry. The maximum size of the base is 6 mm, and the maximum height of the pedestal is 2 mm. The inclination angle θs was set to 20 degrees to 45 degrees. The on-ASIC type GSR sensor is described in detail in Japanese Patent Laid-Open No. 2019-191016 by the inventor of the present invention, which is cited in the present invention.
The present invention uses a compact, high performance magnetic field vector sensor and is not limited to the use of the above two inventions.

The second issue relates to the design of the magnet, which is small enough to be attached to a tooth, and has a positional accuracy of 0.1 mm or less and a azimuth accuracy of 1 degree or less at a distance of 2 cm to 10 cm. should allow measurement of the position and orientation of the magnet body in the magnet coordinate system Cm. Moreover, it is necessary to devise ways to avoid the effects of fluctuations in the surrounding magnetic field environment, especially fluctuations due to movement of the handpiece.

Therefore, the inventor first devised a pulse magnetic field type electromagnet.
A magnetic field vector sensor can detect an oscillating magnetic field and eliminate the effects of ambient magnetic fields. The produced electromagnet had a pulse period of 50 Hz to 1 KHz and a pulse width of 0.1 msec to 5 msec. The excitation current I was determined by considering the number of turns of the coil so that the magnetic needle material could be saturated, that is, the magnetizing force H of the coil was five times or more the coercive force Hc.

Next, we devised an AC electromagnet.
In this case, the band-pass filter of the noise filter of the GSR sensor is set so that the designated frequency can be detected preferentially. The frequency of the electromagnet was set from 10 Hz to 1 KHz. The excitation current I is set to a range of magnetizing force that can linearly magnetize the magnetic needle material, approximately 0.5 times or less than the coercive force Hc, and the number of coil turns is adjusted so that the magnetizing force H of the coil is H<0.5Hc. Determine the current intensity by taking into account

Finally, when a permanent ^magnet is used, it is ^easily affected by the surrounding magnetic field. Special measures are required. Set the initial position and treatment position of the handpiece, and measure the peripheral magnetic field at both positions. Next, the patient is fixed at a predetermined position for surgery, and the grid sensor of the handpiece is used to measure the magnetic field from the magnet placed on the patient's teeth, and the difference between the two is used to measure the magnetic field from the magnet. Using that measurement as a value, the position at the initial position and the treatment position will determine the position of the handpiece. Also, the handpiece is not operated during the magnetic field measurement. Furthermore, it is preferable to use handpieces using non-magnetic materials.

Furthermore, in the second problem, it is necessary to devise a way to specify the magnet coordinate system Cm using one magnet placed on the tooth. With respect to this point, the magnetization direction and the longitudinal direction of a normal magnet are aligned in order to reduce the demagnetizing field. When such a magnet is used, if the direction of magnetization (=longitudinal direction of the magnet marker) is aligned with the longitudinal direction of the teeth and the Z-axis is attached in the vertical direction, the width direction of the magnet will be the horizontal direction. However, the horizontal direction exists 360 degrees, and a specific direction cannot be specified as the X axis. Therefore, an electromagnet whose magnetization direction is in the width direction of the magnet is manufactured, and the longitudinal direction of the magnet is perpendicular to the teeth and attached to the teeth as the Z axis. This problem was solved by finding the Y-axis from the Z-axis and setting the magnet coordinate system Cm with the center of the magnet as the origin.

As a result, the AC electromagnet, the pulse electromagnet, and the permanent magnet have a size width of 6 mm or less and a length of 10 mm or less, and the magnetic moment of the magnet is 5×10 ⁻⁹ to 100×10 ⁻⁹ Wbm. One piece is installed on a specific tooth in the oral cavity with the width direction of the magnet in the vertical direction (Z-axis) and the magnetization vector in the horizontal direction (X-axis), and the center of the magnet is the origin Om, A magnet coordinate system in which the direction of the magnetization vector is the Y-axis, the thickness direction of the magnet body is the Y-axis, and the longitudinal direction is the Z-axis is defined as a Cm system. It is preferable that the attachment error in the vertical direction of the magnet is 0.5 degrees or less.

The design of the magnetic field vector sensor grid (called sensor grid), which is the third issue, is strongly subject to spatial and shape constraints due to the insertion of the handpiece into the oral cavity. Magnetic field vector sensor (hereinafter called sensor) The higher the number of and the closer to the magnet, the better the performance of the magnetic field vector sensor grid, but the more difficult the geometry.
In the present invention, a grid (an example is shown in FIG. 7) in which five or more sensors are arranged in a cylindrical shape on the cylindrical portion of the tip of the handpiece, and a grid plate is arranged on the tip of the handpiece. A prototype of a grid (an example is shown in FIG. 8) in which more than one sensor is arranged was made.
A coordinate system with the center of the magnetic field vector sensor grid as the origin, the direction of the handpiece axis as the Y axis, the lateral direction (horizontal direction) of the sensor grid as the X axis, and the vertical direction (vertical direction) of the sensor grid plate as the Z axis. is C system.

The center of the magnetic field vector sensor grid is the origin Oh, the handpiece axis is the Y axis, the horizontal direction of the sensor grid plate is the X axis, and the vertical direction of the sensor grid plate is the Z axis. An acceleration sensor is installed, the Y-axis is kept horizontal, and the XZ plane, which is the grid sensor plane, is kept vertical. The initial position of the handpiece is such that the XZ plane of the C system of the handpiece faces the XZ plane of the Cm system of the magnetic coordinate system, and the handpiece is brought closer to the oral cavity along the Y axis. will be guided to the designated treatment site in the oral cavity. In this process, the position/orientation relationship between the tip of the handpiece and the magnet is measured using the magnetic field vector sensor grid, and the data is transferred to the sensor grid data processing circuit.

The sensor grid data processing circuit has a function of processing the measurement data measured by the magnetic field vector sensor grid at high speed. Θ and Φ are calculated by the Gauss-Newton method. Here, Θ can be matched by rotating the Z-axis with the angle deviation of the XY planes of both systems. Φ can be made to match by Y-axis rotation with angular displacement of the ZX plane.

The magnetic field vector sensor grid board connects each sensor to a multiplexer MUX, all subsequent data is connected to the final MUX and forwarded to external signal processing circuitry. Although not shown, power supply wiring VDD and ground wiring GND are connected to each sensor so that power can be supplied to all the magnetic field vector sensors when the sensor grid is in operation. The grid electronic circuit board is preferably mounted on the handpiece body.
The assembly accuracy of the sensor grid is required to be as small as possible, and an accuracy of 10 μm or less is preferable.

The fourth task is to devise a calculation program for calculating the position and orientation of the magnet with high precision and excellent real-time performance.
In the magnetic field vector sensor grid, when the magnetic field vector emitted by the magnet is measured as the magnetic field vector at each measurement point, the inventor does not need an iterative process, and adds the deviation between the measured value and the theoretical value as an error. A method of defining an error function as a function obtained by calculating X, Y, Z and Θ, Φ from its minimum value is widely known as the Gauss-Newton method. Using this principle, consider the magnet performance, sensor performance, the number and placement of sensors, the distance between the magnetic marker and the sensor grid, and the shape and size of the object to be placed on the sensor grid, and devise an actual calculation program. There is a difficulty that cannot be said to be the selection of design parameters.
In order to solve this problem, the present inventors have developed a program ( Figure 9) was created.

A calculation program for simultaneously determining the position and orientation based on the Gauss-Newton method is as follows. The center of the magnetic field sensor grid is the origin Oh, the grid surface is the XY plane, and the C coordinate system with the Z axis as the axis perpendicular to the XY plane is specified, and the position of the magnet marker (M (→)) is set ( X, Y, Z), the azimuth is represented by Θ as the rotation angle with respect to the Z axis, and Φ as the rotation angle with respect to the Y axis. Positions (i, j, 0) from i to +i and from -j to +j in the vertical direction, and using the measured values of the magnetic field vectors at these positions, the positions X, Y of the magnet marker (M(→)) , Z and directions Θ and Φ are calculated in the following manner.

(1) First, in step 101, the magnetism at the sensor grid position (i, j, _k ) is measured to obtain the magnetism measurement value mH(→) _ijk .
(2) In step 102, confirm that the ratio S/N of the sensor measurement error value N is 500 or more.
(3) Next, in step 103, the magnetic theoretical value _tH (→) generated by the magnet marker (M(→)) at the (i, j, k)-th sensor position P _ijk of the sensor grid _ijk is obtained from equation (1). Here, the inclination of the magnet is defined as φ as the rotation angle with respect to the Z-axis and θ as the rotation angle with respect to the X-axis. Let r(→) _ijk be the distance vector between the magnet marker (M(→)) and the position P _ijk .
_{( 1 ) _} ^_ _{_ _ _} ^_


(4) Next, in step 104, the difference between the theoretical magnetic value and the measured magnetic value is obtained as the measurement error ε _ijk .
_{eijk =} tH(→) _ijk - _mH (→) _ijk
(5) Next, in step 105, the error function _Eij of the measurement error _εij obtained in step 103 is obtained as the sum of squares of the errors.
E _ijk =Σe _ijk ²
(6) Next, in step 106, x, y, z, θ, and φ that minimize the error sum of squares obtained in step 104 are obtained by the Gauss-Newton method using the following simultaneous equations.
_∂Eijk /∂x=0, _∂Eijk /∂y=0, _∂Eijk /∂z=0,
_∂Eijk /∂φ=0, _∂Eijk /∂θ=0
(7) Next, in step 107, the positions X, Y, and Z of the magnet body marker in the coordinate system Oh-XYZ and the directions of magnetization Θ and Φ of the magnet are obtained from the above equations.
X=x+d×a, Y=y+d×b, Z=z, Θ=θ, Φ=φ

The grid plate is 60 mm x 60 mm, and 15 magnetic field vector sensors with a detection power of 10 nT are arranged in 3 rows of 5 sensors with a row interval of 30 mm and a horizontal interval of 15 mm. A total of 16 sensor grids were fabricated, one in position. Assuming that the magnetic field vector sensor grid is used to measure the magnetic field emitted by a magnetic marker with a strength of 20×10 ⁻⁹ Wbm attached to the tooth, the position and orientation of the magnetic marker are calculated using the above calculation program. decided to ask.

In the experiment to confirm the error, the height was fixed at 40 mm as a reference point, and the magnet marker was moved ±10 mm in the X, Y, and Z directions and rotated ±30 degrees in θ and φ. We repeated the position measurement each time we returned to , and measured its variability. As a result, the calculation error was confirmed, and it was confirmed that the position error was 0.1 mm or less and the orientation error was 0.5 degrees or less, and that the calculation could be performed within a good measurement error range.

On the calculation program, the magnetic moment of the magnet was changed from 1×10 ⁻⁹ to 200×10 ⁻⁹ Wbm, and the sensor noise was changed to 0.1 nT, 1 nT and 10 nT and input. The measurements are also repeated to investigate the effect of magnetic moment and sensor performance on the error of position and orientation calculation. The result is that the positional accuracy of the positions X, Y, Z strongly depends on the distance from the magnet marker, which in turn depends on the distance between the magnet and the sensor grid surface.

As a result, as shown in FIG. 10(a), the position accuracy improved as the magnetic moment increased. When the magnetic moment is quadrupled, the accuracy improves fourfold, when it increases ninefold, it improves ninefold, and when it increases 100fold, it improves 100fold. It was found that doubling the position improves the accuracy of the position calculation by a factor of 10.

Similarly, as a result of azimuth accuracy calculation, as shown in FIG. 10(b), the azimuth accuracy improved as the magnetic moment increased. Similar results were obtained for the effect of the magnetic moment and the effect of the magnetic field sensor spacing on the positional accuracy in the Y direction and the azimuth accuracy of the φ angle.

From the above results, in the present invention, in order to obtain a position accuracy of 0.1 mm or less and an orientation accuracy of 1 degree or less, the magnetic moment of the magnet body marker is set to 5×10 ⁻⁹ to 100×10 ⁻⁹ Wbm and the magnetic field sensor It was decided that the power of detection should be 50 nT or less.

In the present invention, the magnet body is an AC electromagnet or a pulse electromagnet, the size width is 4 mm or less, the length is 10 mm or less, the magnetic moment of the magnet body is 5 × 10 ^-9 to 100 × 10 ^-9 Wbm, and the magnetic field The detection power of the magnetic sensors used in the vector sensor grid was 0.1-10 nT. When using an AC type electromagnet or a pulse type electromagnet, a program was added to determine the fluctuation width of the magnetic field as the strength of the magnetic field emitted from the magnet and use it as a measured value to eliminate the influence of the surrounding magnetic field.

In the case of using a permanent magnet, the peripheral magnetic field distribution was measured in advance, a correction magnetic field was calculated according to the position of the handpiece, and a program was added to subtract the correction magnetic field from the measured magnetic field. Also, in this case, it is necessary to stop the operation of the handpiece, that is, to leave it in a state in which no power is supplied. And preferably the handpiece is non-magnetic.

The fifth problem is to obtain the relative positional relationship between the tip of the handpiece and the treatment position in the oral cavity using a sensor grid, and to ensure that the tip of the handpiece is at a predetermined treatment position with a displacement of 0.1 mm or less. To devise a guidance system capable of guiding so that the misorientation is 1 degree or less.
For this purpose, the present inventor designates the treatment position in the patient's oral cavity on the three-dimensional X-ray CT image as the origin of the magnet attached to the tooth, and calculates the relative relationship between the magnet and the tip of the handpiece. We measured with a sensor grid and devised the following method using the measured values.

The treatment position in the patient's oral cavity is determined on a three-dimensional X-ray image, with the center of the magnet as the origin Om, the direction of magnetization as the X axis, the longitudinal direction of the magnet as the Z axis, and the direction perpendicular to the XZ plane as the Y axis. In the Cm system, the center point of the treatment position is defined as point B, and the position of point B is defined as OmB=(Bx, By, Bz) (FIG. 11).
The inventor also attached a 3-axis accelerometer to the handpiece to measure the degree of inclination, used it to keep the Y-axis of the handpiece horizontal, and attached a magnetic vector sensor grid near the tip of the handpiece. , the origin of the grid is Oh, the longitudinal direction of the handpiece is the Y axis, the horizontal direction of the grid is the X axis, and the vertical direction is the Z axis, and a coordinate system C0 is established. The tip position of the drill of the handpiece was defined as point A, and this position was defined as OhA=(0, L, -H). The maxillofacial region of the patient is fixed with a surgical holder so that the patient's open oral cavity does not move during surgery.

As a relative initial position of both coordinate systems, the XZ plane of the C1 system and the XZ plane of the Cm system are directed to face each other, the tip of the handpiece is brought close to the magnet, and the initial position of the tip of the handpiece is set. The grid system on the handpiece in this state was designated as the C1 system.

Next, in that state, the grid is used to calculate the position R1 and the orientation (θ, φ) of the magnet in the coordinate system C1. By rotating the Y axis by θ degrees and rotating the Y axis by −φ degrees, the azimuth relationship between both coordinate systems was matched. The handpiece system in this state was designated as C2 system.
Viewed from the C2 system, A2B2=OmB2+R2-OhA2. Here, since the orientations of the C2 system and the Cm system match, OmB2=OmB1, and OhA2 is the vector quantity of the C system, so it is the same as OhA1. Since R2 is a vector quantity obtained by the C1 system, R2=Ry(φ1)Rz(θ1)R1 corresponding to the rotation of the coordinate system.

Since the relative positions and orientations of both systems have been grasped, an approach path toward the treatment position is selected on the three-dimensional X-ray image, and the tip A of the handpiece is moved along that path to the treatment site. Move to B. The most basic path is to move the tip A of the handpiece straight to the treatment site B. The angle α on the horizontal plane between R2 and A2B2 is obtained from the inner product of both vectors. Next, the Z-axis is rotated about the rotation axis by α degrees, the Y-axis is directed to the point B2, and this state is defined as the C3 system.
In the C3 system, the grid is used to calculate the position R3 and orientation (θ ₃ , φ ₃ ) of the magnet, A3B3=OmB3+R3-OhA3. Here, OmB3=R(-α)OmB2 is obtained. OhA3 does not change because it is a C-system vector.

From the angle between A3B3 and the Z-axis (0, 0, 1), the tilt angle β of the Y-axis is obtained, the C3 system is rotated by β degrees about the rotation axis of the X-axis, and the Z-axis is directed toward the point B, This state is called C4 system.
In the C4 system, using the grid, calculate the position R4 and orientation (θ ₄ , φ ₄ ) of the magnet to obtain A4B4=OmB4+R4-OhA. where OmB4=R(-β)OmB3.

Since the direction and distance of the approach path are determined, the tip A of the handpiece is moved to the treatment site B along the path, and the coordinate system at that time is defined as the C5 system. In the C5 system, use the grid to calculate the position R5 and orientation (θ ₅ , φ ₅ ) of the magnet and confirm that R5≈0.

Drill holes for implant placement. The direction of drilling is a direction that is tilted at Ex degrees with the X axis as the rotation axis and Ey degrees with the Y axis as the rotation axis. ) degrees and horizontally moved by (Ex−B)×h in the Y-axis direction. Next, the Y-axis is rotated by Ey degrees around the rotation axis, and horizontally moved by Ey×h in the X-axis direction. This state is referred to as C6 system. In the C6 system, using the grid, calculate the position R6 and the orientation (θ ₆ , φ ₆ ) of the magnet and confirm that R6≈0.

After confirming the orientation and position of the handpiece, the drill is rotated and the handpiece is moved by a distance D to form the C7 system. In the C7 system, use the grid to calculate the position R7 and orientation (θ ₆ , φ ₆ ) of the magnet and confirm R7−R6≈D.
After confirmation, return the handpiece to the initial position in the reverse route of the approach path. The handpiece can be guided in the manner described above.

The sixth problem is to fix the patient's maxillofacial area with a fixing holder, but to prevent the patient from moving while the handpiece is being guided, the position and orientation of the patient should be measured at all times. If there is a difference of 1 mm or more from the amount of change that can be calculated from the amount of movement in , the movement is temporarily stopped, the state is set as the C1 system, and the above guidance operation is resumed, and the position accuracy is 0.1 mm or less and the azimuth accuracy is 1 degree or less. Secure.

Alternatively, the angle between the CCD camera system Ca and the intraoral dentition system Cb is initially set by the CCD camera, and the patient's maxillofacial region moves to move the dentition system Cb relative to the Ca system. When a change of 1 mm or more is confirmed, the movement is temporarily stopped, and the guidance operation is restarted as the C1 system in that state to ensure the position accuracy of 0.1 mm or less and the azimuth accuracy of 1 degree or less.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to measure the precise position and orientation of a handpiece in the oral cavity in dental treatment, and to accurately guide the handpiece, thereby realizing robotization of implant treatment. It is expected that

2 is a plan view of a GSR element; FIG. Fig. 3 is an electronic circuit diagram for a GSR sensor; FIG. 3 is a plan view of a magnetic field vector sensor (integrated type) using a GSR sensor; FIG. 10 is a cross-sectional view of a magnetic field vector sensor (integrated type) using a GSR sensor taken along line A1-A2; FIG. 10 is a plan view of a magnetic field vector sensor (assembled type) using a GSR sensor; FIG. 10 is a cross-sectional view of a magnetic field vector sensor (assembled type) using a GSR sensor taken along line B1-B2; Fig. 10 is a perspective view of a cylindrical grid sensor installed at the tip of the handpiece; Fig. 10 is a perspective view of a grid plate type distribution grid sensor installed at the distal end of the handpiece; It is a figure which shows the flowchart of a calculation program. (a) shows the influence of the magnetic moment of the magnet on the positional accuracy, and (b) shows the influence of the magnetic moment on the azimuth accuracy. FIG. 10 is a diagram showing a flow chart of a guidance program; 1 is a conceptual diagram of a guidance system for a handpiece; FIG. It is a figure which shows the coordinate C1 system of the initial state in a guidance system. FIG. 4 is a diagram showing a coordinate system C3 in the guidance system in a movement start state; FIG. 11 shows the coordinate C4 system of the treatment position (B4) state in the guidance system;

A first embodiment of the present invention is as follows.
A magnet is attached to a tooth, and the position/direction detection device of the handpiece attaches one magnet to a specific tooth in the oral cavity so that the length direction of the magnet marker is perpendicular (Z-axis), and the magnetization vector is A coordinate system installed in the horizontal direction (X-axis), with the center of the magnet as the origin Om, the direction of the magnetization vector as the X-axis, the thickness direction of the magnet as the Y-axis, and the longitudinal direction as the Z-axis. Cm, the treatment site in the oral cavity is point B, and the positional relationship from the center of the magnetic marker is determined as OmB,
The handpiece has a magnetic field vector sensor grid consisting of a three-axis acceleration sensor and a magnetic field vector sensor in its main body,
The three-axis acceleration sensor is installed in the body of the handpiece, has a function of measuring an inclination angle η of the handpiece with respect to a horizontal plane, and transfers the measured value to the data processing device,

The magnetic field vector sensor grid is installed near the tip of the handpiece on the patient's oral cavity side, the center of the magnetic field vector sensor grid is the origin Oh, the axis of the handpiece is the Y axis, and the grid of the magnetic field vector sensor grid is It has a coordinate system C with the horizontal direction of the plate as the X axis and the vertical direction of the grid plate as the Z axis, and has a function of measuring the magnetic field generated by the magnet and transferring the measured data to the sensor data processing device. ,
Furthermore, the tip of the handpiece is defined as a point A, the coordinate system is defined as C, and the positional relationship from the center of the grid is defined as OhA,
The sensor data processing device integrally processes the measured values detected by the three-axis acceleration sensor and the magnetic field vector sensor grid and the fixed values of OmB and OhA to determine the treatment position in the cavity and the tip of the handpiece. It consists of a display device that has a function to calculate the position and orientation relationship and informs the operator of those values,

The sensor data processor calculates the positions X, Y, Z and the orientations θ, φ of the magnetic marker by the C system using the magnetic field vector sensor grid measurements, and also calculates the acceleration sensor measurements. to calculate the azimuth η, the azimuth relationship between the C system and the Cm system and the distance between the origins; It is characterized by calculating the position/orientation relationship of the tip of the piece and notifying the operator of it.

Each component will be specifically described below.
<Magnet body>
The magnetic body is a pulse-type electromagnet, an AC-type electromagnet, or a permanent magnet, with a size width of 4 mm or less and a length of 10 mm or less, and a magnetic moment of the magnetic body marker of 5×10 ⁻⁹ to 100×10 ⁻⁹ Wbm. do. The magnetic marker must be small enough to be placed on the tooth, but if it is small, the magnetic moment will be small, the generated magnetic field will be weak, and the positioning accuracy will be lowered.

The pulse magnetic field type electromagnet has a pulse period of 50 Hz to 1 kHz and a pulse width of 0.1 seconds to 5 ms. The excitation current I has a strength that can saturate the magnetic needle material, that is, a current strength that takes into consideration the number of coil turns so that the magnetizing force H is five times or more the coercive force Hc.

The AC electromagnet is a coil wound around a magnetic body, and has a frequency of 10 Hz to 10 kHz. The excitation current I is set to a range of magnetizing force that can linearly magnetize the magnetic needle material, approximately 0.5 times or less than the coercive force Hc, and the number of coil turns is taken into consideration so that the magnetizing force H is H<0.5Hc. be the current intensity.

When a permanent magnet is used, it is easily affected by a surrounding magnetic field, so a magnet body marker having as large a magnetic moment as possible, for example, about 20×10 ⁻⁹ to 100×10 ⁻⁹ Wbm is used. For this purpose, a rare earth magnet having a BHmax of 30MGOe to 55MGOe is used after being subjected to antirust treatment. Although the present invention is not limited to a specific magnet material, it is preferable to use magnets with as large a magnetic force as possible.

<Magnetic field vector sensor>
The GSR sensor repeatedly and rapidly measures the magnetic field with a pulse period of 1 MHz to 5 MHz, averages it, and outputs it at a measurement rate of 200 Hz to 1 KHz.
Magnetic field vector sensors using GSR sensors include an integrated type (Figs. 3 and 4) in which a 3D GSR element is directly formed on the ASIC surface, and an On-ASIC type GSR sensor (size: 2 mm long, 1 mm wide). ) are attached to the four slopes of the ridge of the truncated square pyramid in four-fold symmetry and mirror symmetry (FIGS. 5 and 6).

The integrated type has a detection power of 50 nT or less at a measurement speed of 1 kHz, and the size ranges from 1.2 mm width x 1.2 mm length x 1 mm height to 2 mm width x 2 mm length x 2 mm height. be.
The prefabricated type has a measurement speed of 5 nT or less at 1 kHz, and is an ultra-compact, prefabricated magnetic field vector sensor with a size of 5 mm width×5 mm length×2 mm height or less and excellent magnetic field detection capability.
The present invention uses small, high performance magnetic field vector sensors and is not limited to the above two types of use.

Since the magnetic field vector sensor simultaneously measures the magnetic field emitted from the magnet body and the surrounding magnetic field, the influence of the surrounding magnetic field is eliminated from the measured value and only the magnetic field emitted from the magnet body is detected and used.
In the case of the pulse magnetic field type electromagnet and the AC type electromagnet, the variation width of the detected magnetic field was taken as the magnetic field emitted from the magnet body marker. In the case of permanent magnets, the peripheral magnetic field is measured in advance and corrected by subtracting the value from the measured value.

<Magnetic field vector sensor grid>
Magnetic field vector sensor grids are highly spatially and geometrically constrained due to the intraoral insertion of the handpiece.
The magnetic field vector sensor grid has a magnetic field vector sensor geometrically attached to the tip of the handpiece, and five or more magnetic field vector sensors are arranged on the sensor grid body with a magnetic field vector sensor interval of 3 to 25 mm. The center of the grid is the origin, the direction of the handpiece axis is the Y axis, the lateral direction (horizontal direction) of the sensor grid is the X axis, and the vertical direction (vertical direction) of the sensor grid plate is the Z axis. and

In the first embodiment, the nine magnetic field vector sensors shown in FIG. 7 are geometrically arranged on the cylindrical portion at the tip of the handpiece, and this is used as a grid body.
The magnetic field vector sensor grid connects each magnetic field vector sensor with a multiplexer MUX and all subsequent data is connected with the final MUX and forwarded to external signal processing circuitry. Although not shown, power supply wiring VDD and ground wiring GND are connected to each magnetic field vector sensor so that power can be supplied to all magnetic field vector sensors when the sensor grid is in operation. The grid electronics board is preferably mounted on the handpiece body.
The assembly accuracy of the sensor grid is required to be as small as possible, and an error of 10 μm or less is preferable.

<Measurement by magnetic field vector sensor grid>
For the measurement of the magnetic marker by the magnetic field vector sensor grid, a coordinate system with the center of the grid as the origin, the handpiece axis as the Y axis, the horizontal direction of the grid plate as the X axis, and the vertical direction of the grid plate as the Z axis. A C system is used, an acceleration sensor is installed on the handpiece, the Y axis is kept horizontal, and the XZ plane, which is the grid sensor plane, is kept vertical.
The initial position of the handpiece is such that the XZ plane of the C system of the handpiece and the XZ plane of the Cm system of the magnet face each other. The tip is to be guided to the designated treatment site in the oral cavity. In this process, the position and orientation relationship between the tip of the handpiece and the magnet is measured by the magnetic field vector sensor grid, and the data is transferred to the sensor grid data processing circuit, where the measurement data measured by the magnetic field vector sensor grid is processed at high speed. do.

<Calculation in data processor>
The data processor calculates the position and orientation of the magnetic marker using the grid-based measurement of the magnetic marker. The position (X, Y, Z) and orientations Θ and Φ of the magnet are calculated from the origin of the C coordinate system by the Gauss-Newton method.

The calculation method is as shown in FIG. , the rotation angle with respect to the Z axis is Φ, and the position and orientation (X, Y, Z, Θ and Φ) of the magnet are calculated according to the Gauss-Newton method as follows:

(1) measuring the magnetic field vector _m H (→) _ij at the position (i, j) of each magnetic field vector sensor of the magnetic field sensor grid fixed to the C coordinate system (step 101);
(2) Confirm that the absolute value is 500 times or more in S/N ratio (step 102),
(3) Assuming that the magnet (M(→)) is at the position (x, y, z) and the orientation (θ, φ) with respect to the C coordinate system, the position (i, j) of the magnetic field sensor grid The magnetic field vector produced by
Calculate the theoretical value of _t H(→) _ij (step 103);
(4) calculating the measurement error by e _ij = _t H(→) _{ij −m} H(→) _ij (step 104);
(5) calculating the sum of squares of the errors by E _ij =Σe _ij ² (step 105);
(6) Calculate x, y, z, θ, and φ that minimize the error sum of squares (step 106)
(7) Find the positions X, Y, Z of the magnet and the orientations Θ, Φ (step 107),
Positional accuracy of 0.5mm or less, azimuth accuracy of 1 degree or less, measurement sampling rate of 1 to 50H
In this method, the position and orientation are measured at z, and the data are calculated at a rate of 1 Hz to 50 Hz. By this method, the position and orientation of the magnet in the Ch system can be measured with a sensor grid with a position accuracy of 0.1 mm or less and an orientation accuracy of 1 degree or less.

A second embodiment of the present invention is a method for guiding point A on the distal end of the handpiece to point B to be treated using the first embodiment, and will be described with reference to FIG.
First, from a three-dimensional X-ray CT image map, the position of the magnet marker in the oral cavity is specified, and Cm is determined with the center point Om of the magnet marker and the direction of magnetization as the X axis and the vertical direction of the magnet as the Z axis. Assuming a system, specify the position and orientation of the treatment position B point.
Next, the sensor grid measures the position and orientation of the magnet in the C system, and using the measured values of the orientation θ and φ of the magnet, the C system is rotated by −θ with the Z axis of the C system as the rotation axis. , the angle deviation of the XY plane of both systems can be corrected, and the angle deviation of the ZX plane can be corrected by -φ rotation of the C system about the Y axis as the rotation axis, so that the orientations of both systems can be matched.
A vector AB in the C system can be obtained by transforming the coordinate point of the treatment position B point in the Cm system in the C system after rotation to that in the C system. This vector AB can specify the relative position-orientation relationship between the tip position A point of the handpiece and the treatment position B point.

<Guidance system>
A guidance system in which a hand piece using this method is gripped by a robot hand of an automatic control device to treat a tooth is carried out according to the procedure shown in FIG.
(1) In advance, the coordinate position of the distal end A of the handpiece in the handpiece C system, the coordinate position of the treatment site B in the intraoral magnetic system Cm, and the direction of drilling processing are rotated by β angle around the Y axis as the rotation axis, Next, with the X axis as the rotation axis, enter the γ angle rotation and the depth H of the hole, level the tip of the handpiece, hold it near the magnet installed on the tooth, and place it in the initial position of the guidance system. Assuming that the coordinate system C in this state is C1 (FIG. 13), the magnetic field emitted from the magnet by the sensor grid is measured by the magnetic field vector, and the position (x, y, z) and orientation (θ, φ ) is calculated (step 201).

(2) Rotate the direction of the handpiece by -θ about the Z axis, change the coordinate system C in this state to the C2 system, and calculate the angle α between the treatment position B and the Y axis (step 202).

(3) Rotate the Z-axis of the handpiece at an angle of α around the rotation axis to orient the handpiece in the direction of the treatment site B. After that, in order to orient the drill in the direction of drilling, the drill is rotated by β angle around the Y axis, and then rotated by γ angle around the X axis. ,
By calculating the position (x, y, z) and the orientation (θ, φ) of the magnet, the positional relationship AB between the position A of the tip of the handpiece and the predetermined treatment position B is calculated (step 203).

(4) Move the tip A of the handpiece along the Y-axis, guide it to a predetermined treatment position B, and stop it.
The position (x, y, z) and orientation (θ, φ) of the magnet body were calculated, and the positional relationship AB between the tip position A of the handpiece and the predetermined treatment position B was calculated. The azimuth deviation is 1 mm or less and 1 degree or less, and it is confirmed that the two match (step 204).

(5) If the two do not match, each axis is finely moved to correct the positional deviation so that it is 0.1 mm or less, and each axis is finely rotated about the rotation axis so that the azimuth deviation is 1. The coordinate system C in this state is changed to the C5 system (step 205).

(6) Move the handpiece in the specified direction by the specified distance H to complete the treatment, and let the coordinate system C in this state be the C6 system,
Calculate the position (x, y, z) and orientation (θ, φ) of the magnet body, and confirm that the tip position A of the handpiece is at the depth H in the direction of the specified hole (step 206).

(7) Return the handpiece by H along the Z-axis of the C6 system, then move the distance AB along the Y-axis as it is by the distance vector between origins (-X, -Y, -Z), and By returning to the position of point A, the implant hole drilling can be performed under automatic control (step 207).

Although the patient's maxillofacial region is fixed with a fixed holder while the handpiece is being guided, the following countermeasures should be prepared in advance if the patient moves.
Always measure the position and orientation of the handpiece, and if there is a difference of 1 mm or more from the amount of change that can be calculated from the amount of movement of the handpiece, temporarily stop the movement of the handpiece, and use that state as the C1 system, and perform the above guidance operation. shall be resumed, and a positional accuracy of 0.1 mm or less and an azimuth accuracy of 1 degree or less shall be secured.

Alternatively, the angle between the CCD camera system Ca and the intraoral dentition system Cb is initially set by the CCD camera, and the patient's maxillofacial region moves to move the dentition system Cb relative to the Ca system. If a change of 1 mm or more can be confirmed, the movement shall be temporarily stopped, the state shall be regarded as C1 system, and the above guidance operation shall be resumed to ensure the position accuracy of 0.1 mm or less and the azimuth accuracy of 1 degree or less. .

<Guidance assistance system to the operator>
The third embodiment of the present invention utilizes the second embodiment to provide a system in which the operator holds the handpiece by hand instead of the automatic control device and assists the operator.
(1) The operator memorizes the input values specified on the display screen, the positions of points A and B, the direction of drilling and the depth H of the hole,
Hold the tip of the handpiece horizontally and close to the magnet installed on the tooth. In this state, calculate the position (x, y, z) and orientation (θ, φ) of the magnet body, and the initial position of the guidance system. , the value is conveyed to the operator to assist, and the coordinate system C in this state is set to C1 (step 301).

(2) When rotating the direction of the handpiece by -θ around the Z axis, the operator is assisted by conveying the change in rotation angle during rotation to the operator, and when the amount of rotation reaches θ, the handpiece stops and this state is restored. The coordinate system C is defined as the C2 system, and the angle α between the treatment position B and the Y axis is calculated (step 302).

(3) The operator rotates the handpiece through an α angle around the Z axis of the handpiece, and orients the handpiece in the direction of the treatment site B. After that, in order to orient the drill in the direction of drilling, the Y axis is rotated by an angle of β, and then the X axis is rotated by an angle of γ. , the operator is assisted by conveying the change in rotation angle to the operator, and stops when a predetermined amount of rotation is reached. , z) and the orientation (θ, φ) are calculated, and the positional relationship AB between the position A of the tip of the handpiece and the predetermined treatment position B is calculated (step 303).

(4) The operator moves the tip A of the handpiece along the Y-axis to a predetermined treatment position B. When moving, the position (x, y, z) and orientation (θ, φ) of the magnet are calculated, the positional relationship between the position A of the tip of the handpiece and the predetermined treatment position B is calculated, and the amount of movement is conveyed to the operator to assist, and the coordinate system C in this state is assumed to be the C4 system, and the positional deviation between the two is 0.1 mm or less and the azimuth deviation is 1 degree or less. is confirmed (step 304).

(5) If the positional deviation between the two is 0.1 mm or less and the azimuth deviation is not 1 degree or less, the operator finely moves each axis to correct the positional deviation to 0.1 mm or less. is slightly rotated about the rotation axis to correct the azimuth deviation to 1 degree or less. The correction result is communicated to the operator for assistance, and the coordinate system C in this state is changed to the C5 system (step 305).

(6) When the handpiece is moved in a specified direction by a specified distance H, the amount of movement during movement is communicated to the operator, and when the specified value H is reached, the operator can finish processing. and let the coordinate system C in this state be the C6 system.
The position (x, y, z) and orientation (θ, φ) of the magnet are calculated, and it is confirmed that the tip position A of the handpiece is at the depth H in the direction of the hole (step 306).

(7) The operator returns the handpiece by H along the Z-axis of the C6 system, and then moves the distance AB along the Y-axis by the distance vector between origins (-X, -Y, -Z). In the operation to return to the position of point A in the C4 system, the operator is informed of the movement distance during the operation (step 307),
A handpiece guidance assist system characterized by facilitating implant drilling.

In the fourth embodiment of the present invention, in the second embodiment,
Instead of placing a grid on the cylindrical portion of the tip of the handpiece, a grid plate is placed on the tip of the handpiece, and a grid (Fig. 7) with 12 vector sensors placed on the grid plate is used. , and is the same as the second embodiment except for the shape of the grid.

[Example 1]
Based on the magnetic field vector sensor grid used in the first embodiment, a pulse-type electromagnet is used as the magnet body, and an integrated type consisting of a three-dimensional element and an ASIC is used as the magnetic field vector sensor.

The magnet body is a pulse-type ^{electromagnet} with a size width of 4 mm, a length of 5 mm, and a thickness of 1 mm. did. Permalloy having a magnetic permeability of 30,000 and a coercive force of 80 A/m was used as the magnetic material of the magnetic needle. The number of turns of the coil was 400 times, 100 times per 1 mm, the exciting current was 0.5 A, the magnetizing force H was 200 A/m, and the magnetic needle was saturated.

As a countermeasure against peripheral magnetic field noise, the magnetic field vector sensor detects an oscillating magnetic field corresponding to the strength _Hm of the magnetic field generated by the magnet around the peripheral magnetic field. A magnetic field vector generated from the magnet body is half of the average amplitude of the vibration. Moreover, it was confirmed that there is no influence of environmental fluctuations of the surrounding magnetic field, especially fluctuations of the magnetic field _H0 caused by movement of the handpiece.

Since the magnetic field vector sensor is attached on the cylinder at the tip of the handpiece, we adopted an integrated type, giving priority to its small size. Its performance has a power of 50 nT at a measurement rate of 1 kHz and a size of 1.2 mm x 1.2 mm x 1 mm height.

As shown in Fig. 7, the magnetic field vector sensor grid has 9 sensors arranged in a cylindrical shape on the cylindrical part of the tip of the handpiece. I attached three.
The center of the grid is the center of the plane on which the six sensors are arranged. system.

The method shown in FIG. 9 was used in the first embodiment as a program for calculating the position and orientation of the magnet. As a result, the position and orientation of the magnet body were measured within a range of 5 mm to 50 mm from the origin of the handpiece system, at a measurement speed of 20 Hz, the position accuracy was 0.1 mm or less, and the azimuth accuracy was It could be obtained at 0.7 degrees or less.

[Example 2]
This is a system for guiding the distal end of a handpiece to a treatment position in the oral cavity using the magnet position/orientation detection device of the first embodiment.
As for the initial position of the handpiece, the acceleration sensor is installed on the handpiece, the Y axis is kept horizontal, and the XZ plane, which is the grid sensor plane, is kept vertical. With the C-based XZ plane of the handpiece and the Cm-based XZ plane of the magnet facing each other, the handpiece is brought closer to the oral cavity along the Y-axis, and the initial position of the handpiece is set as close as possible. It was determined.

The sensor grid detected the magnetic field generated by the magnet and transferred the data to the sensor grid data processing circuit. The sensor grid data processing circuit processes measurement data measured by the magnetic field sensor grid at high speed. Φ was calculated by the Gauss-Newton method for the position and orientation of the magnet body in the C system. Here, .theta. is the angular deviation of the XY planes of both systems, which can be matched by Z-axis rotation. φ is an angular deviation of the ZX plane and can be matched by Y-axis rotation.
Using that value, we decided to guide the tip of the handpiece to the designated treatment site in the oral cavity.

As a result of guiding the handpiece according to the flow chart shown in FIG. 12, the tip of the handpiece could be guided with a positional accuracy of 0.1 mm or less and an azimuth accuracy of 0.7 degrees or less.

[Example 3]
In Example 2, an AC electromagnet is used as the magnet.
The magnet was an ^AC electromagnet with a width of 4 mm, a length of 5 mm, and a thickness of 1 mm. Permalloy with a magnetic permeability of 30,000 and a coercive force of 80 A/m is used as the magnetic material of the magnetic needle. m, and the linear region of the permalloy BH curve was utilized.

As a countermeasure against peripheral magnetic field noise, the magnetic field vector sensor detects an oscillating magnetic field corresponding to the magnetic field strength H _m generated by the magnetic marker around the peripheral magnetic field. A half of the average of the vibrating amplitude becomes the magnetic field vector emitted from the magnetic marker. Moreover, it has been confirmed that there is no influence of environmental changes in the surrounding magnetic field, especially changes in the magnetic field _H0 due to movement of the handpiece.

The program for calculating the position and orientation of the magnet was the same as the method shown in FIG. 9 used in the first embodiment. As a result, the position and orientation of the magnet were measured at a speed of 20 Hz within a distance of 5 mm to 50 mm from the origin of the handpiece system. Accuracy could be obtained at 0.7 degrees or less.
As a result of guiding the handpiece according to the flow chart shown in FIG. 12, the tip of the handpiece could be guided with a positional accuracy of 0.1 mm or less and an azimuth accuracy of 0.7 degrees or less.

[Example 4]
In Example 2, an NdFeB magnet was used as a permanent magnet that is a permanent magnet made from a pulse-type electromagnet. As a countermeasure against peripheral magnetic field noise, the peripheral magnetic field was measured at both the initial position of the handpiece and the treatment position. The patient was then held in place during surgery and the handpiece's grid sensor was used to measure the magnetic field from magnets placed on the patient's teeth. Using the difference between the two as a measurement of the magnetic field from the magnet, we decided to determine the position of the handpiece from the position at the initial position and the treatment position. At this time, it is preferable to use a handpiece using a non-magnetic material.
As a result, the tip of the handpiece could be guided with a positional accuracy of 0.1 mm or less and an azimuth accuracy of 0.7 degrees or less.

[Example 5]
In Example 2, as the magnetic field vector sensor, a prefabricated type is used, and a grid is used in which a grid plate is arranged at the tip of the handpiece and 12 magnetic field vector sensors are arranged there.

The assembly type magnetic field vector sensor has a detection power of 5 nT or less at a measurement speed of 1 kHz, and is an ultra-compact magnetic field vector sensor with a size of 5 mm (width) x 5 mm (length) x 2 mm (height) and excellent in magnetic field detection power. . In the method of attaching to the grid plate, the distance from the magnet becomes larger than in the case of installing in the cylindrical portion at the tip. Therefore, we decided to use a magnetic field vector sensor with higher detection power.

The magnetic field vector sensor grid is a transparent sensor grid plate attached to the handpiece, with a width of 60 mm and a length of 45 mm. , and placed one sensor on the handpiece shaft (Fig. 7). The sensor grid substrate is connected with multiplexer MUX column by column, then all data is connected with the final MUX and transferred to the external signal processing circuit. The power wiring system provides power to all sensors for sensor grid operation. The assembly accuracy of the sensor grid was set to 10 μm or less.

The program for calculating the position and orientation of the magnet was the same as the method shown in FIG. 9 used in the first embodiment. As a result, the position and orientation of the magnet marker were measured at a measurement speed of 20 Hz within a distance range of 5 mm to 50 mm from the origin of the handpiece system, the position accuracy was 0.1 mm or less, and the orientation accuracy was It could be obtained at 0.7 degrees or less.
As a result of guiding the handpiece according to the flow chart shown in FIG. 12, the tip of the handpiece was guided with a positional accuracy of 0.1 mm or less and an azimuth accuracy of 0.7 degrees or less.

Although the patient's maxillofacial region is fixed with a fixed holder while the handpiece is being guided, the patient may move, so the following countermeasures should be prepared in advance.
Always measure the position and orientation of the handpiece, and if there is a difference of 1 mm or more from the amount of change that can be calculated from the amount of movement of the handpiece, temporarily stop the movement of the handpiece, and use that state as the C1 system, and perform the above guidance operation. shall be resumed, and a positional accuracy of 0.1 mm or less and an azimuth accuracy of 1 degree or less shall be secured.

Alternatively, the angle between the CCD camera system Ca and the intraoral dentition system Cb is initially set by the CCD camera, and the patient's maxillofacial region moves to move the dentition system Cb relative to the Ca system. If a change of 1 mm or more can be confirmed, the movement shall be temporarily stopped, the state shall be regarded as C1 system, and the above guidance operation shall be resumed to ensure the position accuracy of 0.1 mm or less and the azimuth accuracy of 1 degree or less. .

According to the present invention, it is possible to automatically guide the treatment handpiece for hole processing of the jawbone necessary for implant processing in the oral cavity, and implant treatment can be performed more safely and accurately. expected to be

1: GSR element 11: substrate 12: magnetic wire 13: coil 14: wire terminal 15: wire electrode 16: connection wiring (for wire electrode) 17: coil terminal 18: coil electrode 19: connection Wiring (for coil electrodes)
2: Electronic circuit (electronic circuit of GSR sensor)
21: pulse oscillator, 22: GSR element, 221: wire electrode, 222: coil electrode, 23: parasitic capacitance, 24: circuit input electrode, 25a: first stage detection timing adjustment circuit (T1), 25b: second stage detection Timing adjustment circuit (T2), 26: sample and hold circuit (output side circuit), 27a: 1st stage electronic switch (SW1), 27b: 2nd stage electronic switch (SW2), 28a: 1st stage sample and hold capacitor ( C1), 28b: second-stage sample-and-hold capacitor (C2), 29: amplifier 3: magnetic field vector sensor (integrated type)
31: ASIC, 32: magnetic wire, 33: wire electrode, 34: coil electrode, 35: upper soft magnetic body, 36: lower soft magnetic body, 37: resist layer (photosensitive resin), 38: connection electrode hole, 391: magnetism collection (discharge), 392: magnetism discharge (collection), X1: X1-axis element, X2: X2-axis element, Y1: Y1-axis element, Y2: Y2-axis element 4: Magnetic field vector sensor (assembly type)
40: pedestal (frustum of square pyramid), 401: slope of triangle, 402: slope of rectangle (ridge of square pyramid), 403: upper surface of square, 404: angle of inclination (θs), 41: GSR sensor (on- ASIC type), 411: ASIC, 412: GSR element, 413: magnetic wire 5: hand piece (cylindrical part type)
50: cylindrical portion, 51: magnetic field vector sensor, 52: drill tip, Oh: origin 6: handpiece (axis grid plate type)
60: shaft, 61: magnetic field vector sensor grid, 62: grid plate (installed on shaft), 63: magnetic field vector sensor, 64: drill, 65: acceleration sensor, Oh: origin 7: three-dimensional X image map 71: hand piece, 710: origin of handpiece Oh, 711: positional relationship OhA
72: magnet body (pulse-type electromagnet), 720: origin Om of magnet body, 721: direction of magnetization (X-axis), 722: positional relationship OmB
73: Bone 74: Teeth A: Handpiece Tip B: Treatment Position 8: Coordinate System C in Guidance System
801: Magnetic field vector sensor (sensors that make up the magnetic field vector sensor grid)
81: handpiece, 8101: C1 system origin Oh1, 8103: C3 system origin Oh3, 8104: C4 system origin Oh4
82: magnet, 820: magnet origin Om, 821: angle θ, 822: α rotation angle 83: tooth C1: initial state coordinate system, C3: handpiece movement start state coordinate system, C4: handpiece Coordinate system R1: position of the magnet in the C1 system, R3: position of the magnet in the C3 system, R4: position of the magnet in the C4 system when the treatment position is reached.

The present invention attaches mini magnets to the teeth in the oral cavity, attaches a magnetic field vector sensor grid to the handpiece, measures the positional relationship between the handpiece and the magnet, and determines the position of the handpiece based on that. The present invention relates to a detection device and a guidance system for measuring azimuth with high precision and in real time.

In the field of dental implant treatment, there is an increasing need for the development of a system for highly accurate measurement of the positional orientation relationship between the implant embedding hole and the handpiece and for guiding the handpiece.
A method for optically measuring the position-orientation relationship has been developed (Non-Patent Document 1), but the accuracy is poor and the handpiece cannot be directly guided in the oral cavity. Therefore, a complicated indirect method, that is, to create an intraoral model and use optical markers attached to the model and the mouthpiece, acquires position-orientation data of the handpiece and the optical marker on the model. While performing treatment on the model, the guidance trajectory of the handpiece at that time is stored in the computer, and based on this data, the actual treatment is automatically controlled. Treatment is performed while correcting the relative positional relationship by measuring the positional relationship between the handpiece and the optical marker attached to the mouthpiece.

The magnetic type measures the position and orientation of the handpiece by attaching a magnetic marker to the teeth as a reference in the oral cavity and attaching a magnetic sensor grid that is fixed and installed on the patient's side. Although it is simple, it is very difficult to achieve excellent measurement accuracy because only a small magnetic marker with a width of 4 mm and a length of 8 mm can be used if the tooth size is the maximum size. Moreover, a magnetic field vector sensor capable of sensitively measuring minute magnetic fields emitted by external magnetic markers has not yet been developed. Only significantly inferior ones have been developed. In addition, the measurement speed of the existing developed product is as slow as 1 Hz, and significant improvement is required.

Japanese Patent Application Laid-Open No. 2002-200001 discloses a magnet type position/orientation calculation system. It consists of an NdFeB magnet (size: 0.8 mm x 2.5 mm, three magnets) with a magnetic moment of about 4.8 × 10 ^-9 Wbm, and an FG sensor with a magnetic field detection power of about 1 nT. A three-axis magnetic field sensor is used to enable measurement of the position of the magnetic marker. According to this disclosure, the magnet side moves, and the method traces the position of the magnet body marker with an externally fixed magnetic sensor. The magnetic markers attached to the handpiece and teeth mean that the handpiece and the patient themselves move, and the positions of the magnetic markers also move, so this disclosure cannot be used as it is.

Furthermore, the positional accuracy is about 4 mm, which is significantly inferior to the positional accuracy of 0.5 mm or less required for implant treatment. The main reason for this is thought to be that since no magnetic field vector sensor is used, there is a large deviation between the positions of the mutual measurement values of the three-axis magnetic field sensors. Although the three-axis magnetic sensor used (Patent Document 1, FIG. 2) is not accurately described in this document, assuming that the diameter of the magnetic field sensor is 3 mm to 5 mm, approximately each magnetic field sensor measures The positions are shifted from each other by about 1.5 mm to 2.5 mm, and it is believed that this mutual error causes a significant loss of the positional accuracy of the present disclosure.
Also, since this disclosure does not use a magnetic field vector sensor, it cannot be calculated according to the Gauss-Newton method. Therefore, an iterative process utilizing magnetic field gradients is performed to obtain X, Y, Z, Θ, and Φ that minimize the error between the measured and theoretical values. There seems to be a problem with real-time performance. In fact, Patent Document 1 does not describe the measurement speed. As described above, the position of the magnetic marker cannot be measured with high accuracy in the present disclosure that does not presuppose the magnetic field vector sensor.

As a three-axis magnetic field sensor, there is an electronic compass (Patent Document 2) of Aichi Steel Co., Ltd., which uses an MI sensor. , the magnetic field measurement positions in the Z-axis direction are shifted by about 1 mm, and the magnetic field vector at a predetermined position cannot be measured. Also, the magnetic field detection power is as low as 200 nT. Even if this product is applied to the invention of Patent Document 1, improvement in the positional accuracy of the magnetic marker cannot be expected. In order to improve the positional accuracy, it is important to use a magnetic field vector sensor capable of pinpoint magnetic field vector measurement using a three-dimensional magnetic sensor instead of a three-axis magnetic field sensor for magnetic field measurement.

As a magnetic field vector sensor, there is an electronic compass (Patent Document 3) manufactured by Asahi Kasei Corporation as a magnetic field measuring device using a Hall sensor. It is a combination of four Hall elements and one permalloy magnetic collector, and the sensor element spacing is about 1 mm, and it is possible to measure the magnetic field vector at a pinpoint predetermined position. Although it is possible to fabricate a sensor grid arranged at a high density, there is a problem that the magnetic field detection capability is only about 10 mG (=1000 nT), and minute magnetic fields cannot be measured.

A magnetic field vector sensor using a GMR sensor is introduced in US Pat. It has a small size of 2 mm x 2 mm, a detection power of about 500 nT, and a problem that the measurement accuracy of Hx and Hy differs from that of Hz. As a result, there is a problem that a minute magnetic field cannot be measured.

As a magnetic field vector sensor using an FG sensor, there is an nT meter (Non-Patent Document 2) manufactured by MTI. Although the detection power is at the 1 nT level, the elements are attached to the six sides of a 30 mm cube, and the spacing between the sensor elements is about 30 mm. You will be measuring the gradient and cannot pinpoint the magnetic field measurement at a particular location. It is also larger than the size of the handpiece and cannot be attached to it.

As a type using a GSR sensor (Patent Document 5), there is an electronic compass (Patent Document 6) by Magnedesign. It is a combination of four GSR elements and a pair of permalloy magnetic collectors, and the sensor element spacing is about 0.5 mm. It is possible to measure the magnetic field vector at a pinpoint predetermined position, and the magnetic field detectability is also measured. It is 100nT or less at a speed of 200Hz, which is superior to Hall sensors and MI sensors. However, the required magnetic field detection power is insufficient when compared to 50 nT or less at a measurement speed of 1 KHz. If this product is applied to the invention of Patent Document 1, improvement in the positional accuracy of the magnetic marker can be expected. Moreover, since it is an iterative process method, the measurement speed must be less than 1 Hz.

In order to accurately and quickly measure the position and orientation of a small magnet placed on a detection object, it is necessary to develop a compact magnetic field vector sensor with high magnetic field detection capability. Specifically, there is a demand for the development of a magnetic field vector sensor that can detect a minute magnetic field of 50 nT or less at a measurement speed of 1 kHz and can measure the magnetic field vector at a pinpoint predetermined position in a minute space of 4 mm × 4 mm × 2 mm or less. ing.

Regarding the algorithm for calculating the position and orientation of the magnet, as a method of simultaneously obtaining the position and orientation of the magnet using the magnetic field vector sensor grid, an error function is defined in Non-Patent Document 3, and the coordinate components that minimize the error function A method for determining the three components of X, Y, and Z is described. However, it does not describe how to obtain .theta. and .phi., and does not describe how to obtain the three coordinate components X, Y and Z and the directions .theta. and .phi. from the error function. Note that the measurement position error in Non-Patent Document 3 is as large as 5.5 mm, which is not of a practical level. Strictly speaking, the magnetic field vector sensor described in this document has a deviation of 1.8 mm between the measurement positions of the three-axis sensor. It seems to be because Furthermore, the size of the sensor used is too large to be attached to the handpiece.

In developing a magnetic position and orientation measurement and guidance system for a dental handpiece, in order to improve the accuracy of the conventional magnetic positioning method, we developed a high-performance magnetic field vector sensor and installed a sensor grid on a small handpiece. It is necessary to develop a measurement system that can accurately measure the relative position and orientation of the handpiece and the magnetic body inside the oral cavity every moment, regardless of the movement of the handpiece and the magnetic body inside the oral cavity. In terms of performance, there is a demand for the development of a device that has a measurement speed of 1 Hz to 50 Hz, a position accuracy of 0.1 mm or less, and performance that is about 100 times that of conventional devices.

Japanese Patent Application Laid-Open No. 2001-524012 Japanese Patent No. 3781056 Japanese Patent Application Laid-Open No. 2004-61380 Japanese Patent Publication No. 2013-518273 Japanese Patent No. 6506466 Japanese Patent No. 6021239 Japanese Patent No. 6021239

Naotomo Kondo, Yutaro Oyamada: "Current status and future of robotic surgery in oral implant treatment", Journal of Japan Prosthodontics, 13-21, 2021 MTI Co., Ltd. Website Product information FGS3-1000 Takashi Nagaoka, Akihiko Uchiyama: Tateishi Science and Technology Foundation Grant Research Report: No. 15, pp. 52-55 (2006) Y.Honkura, S.Honkura ; JMMM513(2020)167240

The present invention measures the position and azimuth relationship of the magnet by using a magnetic field sensor grid in which the magnet installed on the tooth is installed on the handpiece, and uses the measured values to determine the position of the tip of the handpiece and the oral cavity. It is to measure the relative position and azimuth relationship with the treatment position in the inside with high accuracy and realize a handpiece guidance system using it. For this purpose, we need to develop a technique for accurately measuring the position/orientation relationship between the magnet attached to the tooth and the tip of the handpiece.

According to the present invention, the magnet as the magnet marker is an AC electromagnet, a pulse electromagnet, or a permanent magnet with a width of 6 mm or less, a length of 10 mm or less, and a magnetic moment of 5×10 mm. ^-9 to 100 × 10 ^-9 Wbm, one magnet is placed on a specific tooth in the oral cavity, the magnetization vector is set in the horizontal direction (X axis), and the center of the magnet is the origin. Let the magnet coordinate system with the direction of the vector as the X axis, the thickness direction of the magnet as the Y axis, and the longitudinal direction as the Z axis be the Cm system,
The magnetic field vector sensor grid has at least five magnetic field vector sensors arranged in a grid on the grid attached to the handpiece. Let the coordinate system with the horizontal X-axis and the vertical direction of the grid as the Z-axis be the C system,
Position/azimuth detector for a handpiece that can measure the positional relationship and azimuth relationship between both coordinate systems at a measurement speed of 1 Hz to 50 Hz or less, with a position accuracy of 0.1 mm or less, and an azimuth accuracy of 1 degree or less. It is about.

As a technical development task for that purpose, the first task is to develop a magnetic field vector sensor having a detection power of 50 nT or less at a measurement speed of 1 KHz. A GSR sensor has been developed as a small sensor capable of detecting minute magnetic fields. The object is to devise a magnetic field vector sensor structure that can make the measurement error the same.

A second issue relates to the design of the magnet. The size of the magnet is so small that it can be attached to the teeth, and the positional accuracy is 0.1 mm or less and the azimuth accuracy is 1 degree or less even at a distance of 20 mm to 100 mm. need to make it possible. In addition, it is necessary to devise ways to avoid the effects of fluctuations in the surrounding magnetic field environment, especially fluctuations due to movement of the handpiece. Furthermore, it is necessary to devise a way to specify the magnet coordinate system Cm using one magnet placed on the tooth.

A third challenge is to design a geometrically designed magnetic field vector sensor grid on the handpiece. As the number of magnetic field vector sensors on the grid increases, the accuracy of position and azimuth calculations improves. Proper placement is important.

The fourth task is to devise a calculation program for calculating the position and orientation of the magnet with high precision and excellent real-time performance. With the magnetic field vector sensor grid, when the magnetic field vector emitted by the magnetic marker is measured as the magnetic field vector at each measurement point, no iterative process is required. A method of defining a function and calculating X, Y, Z and θ, φ from its minimum value is widely known as the Gauss-Newton method. Using this principle, we consider the magnet performance, sensor performance, the number and arrangement of sensors, the distance between the magnetic marker and the magnetic field vector sensor grid, and the shape and size of the target product on which the magnetic field vector sensor is placed on the grid. There is a difficulty that can not be said to be the selection of design parameters to devise a calculation program for .

The fifth problem is to obtain the relative positional relationship between the tip of the handpiece and the treatment position in the oral cavity using the magnetic field vector sensor grid, and to ensure that the tip of the handpiece is at a predetermined treatment position with a displacement of 0.5. The present invention relates to a guidance system capable of providing guidance such that the misorientation is 1 mm or less and the misorientation is 1 degree or less.

A sixth issue is countermeasures against movement of the patient during guidance of the handpiece.

The conventional method obtains the position and orientation of the moving magnet in a grid system fixed to the device (in other words, the coordinate system of the device), and the positional relationship between the device and the magnet can be grasped as it is. However, the subject of the present invention is the case where the orientation and position of the handpiece fluctuate, and the position and orientation of the magnet also slightly fluctuate according to the movement of the patient. In other words, both are active, and simply obtaining the relative position/orientation relationship between the two does not allow the operator of the handpiece or a mechanical control device such as a robot to grasp the position/orientation of the handpiece. information necessary for control cannot be obtained. It is necessary to devise a new algorithm for measuring the position and orientation of such a working grid system and magnets.

The present invention consists of a magnet, a magnetic field vector sensor, a magnetic field vector sensor grid, a sensor grid data processing circuit, a position/orientation calculation program, a data processing device incorporating it, and a handpiece guidance system.
Therefore, the present inventor first worked on the development of a magnetic field vector sensor having high detection power, which is the first problem.

As a magnetic field vector sensor using a GSR sensor, as disclosed in Patent Documents 6 and 7, it has a detection power of 100 nT or less at a measurement speed of 200 Hz, and its size is the size of an integrated circuit 1.4×1. Considering 4 mm, it is about 2×2 mm.

Here, the GSR sensor is described in detail in Patent Document 5, which is cited in the present invention. As shown in FIG. 1, the GSR sensor consists of a detection coil formed of a magnetic field detection magnetic wire having conductivity on a substrate, a circulating coil wound around the wire, two electrodes for wire conduction, and an electrode for detecting coil voltage. A means for applying a pulse current having a frequency of GHz to a GSR element composed of wiring connecting two electrodes and a magnetic wire, and a coil voltage generated when the pulse current is applied are detected, and the coil voltage is detected by an external magnetic field H It is an ultrasensitive micro magnetic sensor consisting of an electronic circuit (Fig. 2) that converts to

The present inventors have tried to increase the length of the GSR element, increase the number of coil turns, improve the shape of permalloy and the magnetic circuit to strengthen the magnetic gathering force of the magnetic field Hz in the Z-axis direction, and directly apply the magnetic field to the ASIC surface. By forming and connecting to the ASIC circuit with via holes for electrodes, the performance of the magnetic field vector sensor can be improved to 50 nT or less detection power at a measurement rate of 1 KHz without changing the sensor size. It was decided to use the sensor in the present invention. ASIC is an application specific integrated circuit.

This integrated magnetic field vector sensor will be described with reference to FIGS.
On the ASIC 31, the X1 element and the X2 element are symmetrically arranged in the X-axis direction with the origin as the center, and the Y1 element and the Y2 element are symmetrically arranged in the Y-axis direction orthogonal to the X-axis direction. Each element is coated on the upper surface of the ASIC, a magnetic wire 32 is arranged in a grooved resist layer, and a detection coil and four electrodes (33, 34) are formed around the magnetic wire 32. The four electrodes (33, 34) are connected to the ASIC through connecting electrode holes 38. FIG. One upper soft magnetic body 35 is formed above the magnetic wire 32 at the origin, and lower soft magnetic bodies 36 are formed below the magnetic wire 32 at the ends of the four elements opposite to the origin. ing.
With this configuration, the magnetic field in the X-axis direction and the Y-axis direction is detected, and the magnetic field in the Z-axis direction is collected 391 (or discharged) by the upper soft magnetic body 35. It is detected by being discharged (or collected) by 392 . Therefore, the magnetic field vector (Hx, Hy, Hz) at the origin is detected.

A GSR sensor is used to measure a magnetic field at a rate of 1 MHz to 5 MHz, average it, and output it at a measurement rate of 200 Hz to 500 KHz. The detection power of the GSR sensor increases in proportion to the length of the magnetic wire. In order to measure a minute magnetic field of 5 nT or less at a measurement speed of 1 kHz in a minute space range, the present inventor directly molded a GSR element with a long magnetic wire length of 1 to 2.4 mm on the surface of an ASIC to achieve a small size. An On-ASIC type GSR sensor (Non-Patent Document 4) was manufactured, and using it, an assembly type magnetic field vector sensor was developed and used in the present invention.

As shown in FIGS. 5 and 6, the assembly-type magnetic field vector sensor consists of four On-ASIC type GSR sensors 41 (size: 2 mm long, 1 mm wide) attached to the ridge line 402 of the truncated square pyramid 40. It is affixed on four slopes in four-fold symmetry and mirror symmetry. The maximum size of the base is 6 mm, and the maximum height of the pedestal is 2 mm. The inclination angle θs was set to 20 degrees to 45 degrees. The on-ASIC type GSR sensor is described in detail in Japanese Patent Laid-Open No. 2019-191016 by the inventor of the present invention, which is cited in the present invention.
The present invention uses a compact, high performance magnetic field vector sensor and is not limited to the use of the above two inventions.

The second issue relates to the design of the magnet, which is small enough to be attached to a tooth, and has a positional accuracy of 0.1 mm or less and a azimuth accuracy of 1 degree or less at a distance of 2 cm to 10 cm. should allow measurement of the position and orientation of the magnet body in the magnet coordinate system Cm. Moreover, it is necessary to devise ways to avoid the effects of fluctuations in the surrounding magnetic field environment, especially fluctuations due to movement of the handpiece.

Therefore, the inventor first devised a pulse magnetic field type electromagnet.
A magnetic field vector sensor can detect an oscillating magnetic field and eliminate the effects of surrounding magnetic fields. The produced electromagnet had a pulse period of 50 Hz to 1 KHz and a pulse width of 0.1 msec to 5 msec. The excitation current I was determined by considering the number of turns of the coil so that the magnetic needle material could be saturated, ie, the magnetizing force H of the coil was five times or more the coercive force Hc.

Next, we devised an AC electromagnet.
In this case, the band-pass filter of the noise filter of the GSR sensor is set so that the designated frequency can be detected preferentially. The frequency of the electromagnet was set from 10 Hz to 1 KHz. The excitation current I is set to a range of magnetizing force that can linearly magnetize the magnetic needle material, approximately 0.5 times or less than the coercive force Hc, and the number of coil turns is adjusted so that the magnetizing force H of the coil is H<0.5Hc. Determine the current intensity by taking into account

Finally, when a permanent ^magnet is used, it is ^easily affected by the surrounding magnetic field. Special measures are required. Set the initial position and treatment position of the handpiece, and measure the peripheral magnetic field at both positions. Next, the patient is fixed at a predetermined position for surgery, and the grid sensor of the handpiece is used to measure the magnetic field from the magnet placed on the patient's teeth, and the difference between the two is used to measure the magnetic field from the magnet. Using that measurement as a value, the position at the initial position and the treatment position will determine the position of the handpiece. Also, the handpiece is not operated during the magnetic field measurement. Furthermore, it is preferable to use handpieces using non-magnetic materials.

Furthermore, in the second problem, it is necessary to devise a way to specify the magnet coordinate system Cm using one magnet placed on the tooth. With respect to this point, the magnetization direction and the longitudinal direction of a normal magnet are aligned in order to reduce the demagnetizing field. When such a magnet is used, if the direction of magnetization (=longitudinal direction of the magnet marker) is aligned with the longitudinal direction of the teeth and the Z-axis is attached in the vertical direction, the width direction of the magnet will be the horizontal direction. However, the horizontal direction exists 360 degrees, and a specific direction cannot be specified as the X axis. Therefore, an electromagnet whose magnetization direction is in the width direction of the magnet is manufactured, and the longitudinal direction of the magnet is perpendicular to the teeth and attached to the teeth as the Z axis. This problem was solved by finding the Y-axis from the Z-axis and setting the magnet coordinate system Cm with the center of the magnet as the origin.

As a result, the AC electromagnet, the pulse electromagnet, and the permanent magnet have a size width of 6 mm or less and a length of 10 mm or less, and the magnetic moment of the magnet is 5×10 ⁻⁹ to 100×10 ⁻⁹ Wbm. One piece is installed on a specific tooth in the oral cavity with the width direction of the magnet in the vertical direction (Z-axis) and the magnetization vector in the horizontal direction (X-axis), and the center of the magnet is the origin Om, A magnet coordinate system in which the direction of the magnetization vector is the Y-axis, the thickness direction of the magnet body is the Y-axis, and the longitudinal direction is the Z-axis is defined as a Cm system. It is preferable that the attachment error in the vertical direction of the magnet body is 0.5 degrees or less.

The design of the magnetic field vector sensor grid (called sensor grid), which is the third issue, is strongly subject to spatial and shape constraints due to the insertion of the handpiece into the oral cavity. Magnetic field vector sensor (hereinafter called sensor) The higher the number of and the closer to the magnet, the better the performance of the magnetic field vector sensor grid, but the more difficult the geometry.
In the present invention, a grid (an example is shown in FIG. 7) in which five or more sensors are arranged in a cylindrical shape on the cylindrical portion of the tip of the handpiece, and a grid plate is arranged on the tip of the handpiece. A prototype of a grid (an example is shown in FIG. 8) in which more than one sensor is arranged was made.
A coordinate system with the center of the magnetic field vector sensor grid as the origin, the direction of the handpiece axis as the Y axis, the lateral direction (horizontal direction) of the sensor grid as the X axis, and the vertical direction (vertical direction) of the sensor grid plate as the Z axis. is C system.

The center of the magnetic field vector sensor grid is the origin Oh, the handpiece axis is the Y axis, the horizontal direction of the sensor grid plate is the X axis, and the vertical direction of the sensor grid plate is the Z axis. An acceleration sensor is installed, the Y-axis is kept horizontal, and the XZ plane, which is the grid sensor plane, is kept vertical. The initial position of the handpiece is such that the XZ plane of the C system of the handpiece faces the XZ plane of the Cm system of the magnet coordinate system, and the handpiece is brought closer to the oral cavity along the Y axis. to the designated treatment position in the oral cavity. In this process, the position/orientation relationship between the tip of the handpiece and the magnet is measured using the magnetic field vector sensor grid, and the data is transferred to the sensor grid data processing circuit.

The sensor grid data processing circuit has a function of processing the measurement data measured by the magnetic field vector sensor grid at high speed. Θ and Φ are calculated by the Gauss-Newton method. Here, Θ can be matched by rotating the Z-axis with the angle deviation of the XY planes of both systems. Φ can be made to match by Y-axis rotation with angular displacement of the ZX plane.

The magnetic field vector sensor grid board connects each sensor to a multiplexer MUX, all subsequent data is connected to the final MUX and forwarded to external signal processing circuitry. Although not shown, power supply wiring VDD and ground wiring GND are connected to each sensor so that power can be supplied to all the magnetic field vector sensors when the sensor grid is in operation. The grid electronics board is preferably mounted on the handpiece body.
The assembly accuracy of the sensor grid is required to be as small as possible, and an accuracy of 10 μm or less is preferable.

The fourth task is to devise a calculation program for calculating the position and orientation of the magnet with high precision and excellent real-time performance.
In the magnetic field vector sensor grid, when the magnetic field vector emitted by the magnet is measured as the magnetic field vector at each measurement point, the inventor does not need an iterative process, and adds the deviation between the measured value and the theoretical value as an error. A method of defining an error function as a function obtained by calculating X, Y, Z and Θ, Φ from its minimum value is widely known as the Gauss-Newton method. Using this principle, consider the magnet performance, sensor performance, the number and arrangement of sensors, the distance between the magnetic marker and the sensor grid, and the shape and size of the object to be placed on the sensor grid, and devise an actual calculation program. There is a difficulty that cannot be said to be the selection of design parameters.
In order to solve this problem, the present inventors have developed a program ( Figure 9) was created.

A calculation program for simultaneously determining the position and orientation based on the Gauss-Newton method is as follows. The center of the magnetic field sensor grid is the origin Oh, the grid surface is the XY plane, and the C coordinate system with the Z axis being the axis perpendicular to the XY plane is specified, and the position of the magnetic marker ( ) is (X, Y, Z), the azimuth is Θ as the rotation angle with respect to the Z axis, and Φ as the rotation angle with respect to the Y axis. Positions (i, j, 0) from -j to +j in the vertical direction, and using the measured values of the magnetic field vectors at these positions, the positions X, Y, Z and the directions Θ, Φ of the magnetic marker ( ) It is calculated in the following manner.

(1) First, in step 101, the magnetism at the sensor grid position (i, j, _k ) is measured to obtain the magnetism measurement value mH(→) _ijk .
(2) In step 102, confirm that the ratio S/N of the sensor measurement error value N is 500 or more.
(3) Next, in step 103, the magnetic theoretical value tH(→) _ijk generated by the magnet marker ( ) at the (i, j, _k )-th sensor position P _ijk of the sensor grid is expressed by the formula ( 1). Here, the inclination of the magnet is defined as φ as the rotation angle with respect to the Z-axis and θ as the rotation angle with respect to the X-axis. Let _ijk be the distance vector between the magnet marker ( ) and the position _Pijk .
_t H(→) _ijk = 1/4πμ _o {−M(→)/r _ijk ³ +3(M(→) r(→) _ijk )r(→) _ijk /r _ijk ⁵ } (1)

(4) Next, in step 104, the difference between the theoretical magnetic value and the measured magnetic value is obtained as the measurement error ε _ijk .
_{eijk =} tH(→) _ijk - _mH (→) _ijk
(5) Next, in step 105, the error function _Eij of the measurement error _εij obtained in step 103 is obtained as the sum of squares of the errors.
E _ijk =Σe _ijk ²
(6) Next, in step 106, x, y, z, θ, and φ that minimize the error sum of squares obtained in step 104 are obtained by the Gauss-Newton method using the following simultaneous equations.
_∂Eijk /∂x=0, _∂Eijk /∂y=0, _∂Eijk /∂z=0,
_∂Eijk /∂φ=0, _∂Eijk /∂θ=0
(7) Next, in step 107, the positions X, Y, and Z of the magnet body marker in the coordinate system Oh-XYZ and the directions of magnetization Θ and Φ of the magnet are obtained from the above equations.
X=x+d×a, Y=y+d×b, Z=z, Θ=θ, Φ=φ

The grid plate is 60 mm x 60 mm, and 15 magnetic field vector sensors with a detection power of 10 nT are arranged in 3 rows of 5 sensors with a row interval of 30 mm and a horizontal interval of 15 mm. A total of 16 sensor grids were fabricated, one in position. Assuming that the magnetic field vector sensor grid is used to measure the magnetic field emitted by a magnetic marker with a strength of 20×10 ⁻⁹ Wbm attached to the tooth, the position and orientation of the magnetic marker are calculated using the above calculation program. decided to ask.

In the experiment to confirm the error, the height was fixed at 40 mm as a reference point, and the magnet marker was moved ±10 mm in the X, Y, and Z directions and rotated ±30 degrees in θ and φ. We repeated the position measurement each time we returned to , and measured its variability. As a result, the calculation error was confirmed, and it was confirmed that the position error was 0.1 mm or less and the orientation error was 0.5 degrees or less, and that the calculation could be performed within a good measurement error range.

On the calculation program, the magnetic moment of the magnet was changed from 1×10 ⁻⁹ to 200×10 ⁻⁹ Wbm, and the sensor noise was changed to 0.1 nT, 1 nT and 10 nT and input. The measurements are also repeated to investigate the effect of magnetic moment and sensor performance on the error of position and orientation calculation. The result is that the positional accuracy of the positions X, Y, Z strongly depends on the distance from the magnet marker, which in turn depends on the distance between the magnet and the sensor grid surface.

As a result, as shown in FIG. 10(a), the position accuracy improved as the magnetic moment increased. When the magnetic moment is quadrupled, the accuracy improves fourfold, when it increases ninefold, it improves ninefold, and when it increases 100fold, it improves 100fold. It was found that doubling the position improves the accuracy of the position calculation by a factor of 10.

Similarly, as a result of azimuth accuracy calculation, as shown in FIG. 10(b), the azimuth accuracy improved as the magnetic moment increased. Similar results were obtained for the effect of the magnetic moment and the effect of the magnetic field sensor spacing on the positional accuracy in the Y direction and the azimuth accuracy of the φ angle.

From the above results, in the present invention, in order to obtain a position accuracy of 0.1 mm or less and an orientation accuracy of 1 degree or less, the magnetic moment of the magnet body marker is set to 5×10 ⁻⁹ to 100×10 ⁻⁹ Wbm and the magnetic field sensor It was decided that the power of detection should be 50 nT or less.

In the present invention, the magnet body is an AC electromagnet or a pulse electromagnet, the size width is 4 mm or less, the length is 10 mm or less, the magnetic moment of the magnet body is 5×10 ⁻⁹ to 100×10 ⁻⁹ Wbm, and the magnetic field The detection power of the magnetic sensors used in the vector sensor grid was 0.1-10 nT. When using an AC type electromagnet or a pulse type electromagnet, a program was added to determine the fluctuation width of the magnetic field as the strength of the magnetic field emitted from the magnet and use it as a measured value to eliminate the influence of the surrounding magnetic field.

In the case of using a permanent magnet, the peripheral magnetic field distribution was measured in advance, a correction magnetic field was calculated according to the position of the handpiece, and a program was added to subtract the correction magnetic field from the measured magnetic field. Also, in this case, it is necessary to stop the operation of the handpiece, that is, to leave it in a state in which no power is supplied. And preferably the handpiece is non-magnetic.

The fifth problem is to obtain the relative positional relationship between the tip of the handpiece and the treatment position in the oral cavity using a sensor grid, and to ensure that the tip of the handpiece is at a predetermined treatment position with a displacement of 0.1 mm or less. To devise a guidance system capable of guiding so that the misorientation is 1 degree or less.
For this purpose, the present inventor designated the treatment position in the patient's oral cavity on the three-dimensional X-ray CT image as the origin of the magnet attached to the tooth, and determined the relative relationship between the magnet and the tip of the handpiece. We measured with a sensor grid and devised the following method using the measured values.

The treatment position in the patient's oral cavity is determined on the three-dimensional X-ray image, with the center of the magnet as the origin Om, the direction of magnetization as the X axis, the longitudinal direction of the magnet as the Z axis, and the direction perpendicular to the XZ plane as the Y axis. In the Cm system, the center point of the treatment position is point B (hereinafter referred to as treatment position B) , and the position of point B is OmB = (Bx, By, Bz). (Fig. 11).
The inventor also attached a 3-axis accelerometer to the handpiece to measure the degree of inclination, used it to keep the Y-axis of the handpiece horizontal, and attached a magnetic vector sensor grid near the tip of the handpiece. , the origin of the grid is Oh, the longitudinal direction of the handpiece is the Y axis, the horizontal direction of the grid is the X axis, and the vertical direction is the Z axis, and a coordinate system C0 is established. The tip position of the drill of the handpiece was defined as point A (hereinafter referred to as tip position A) , and this position was defined as OhA=(0, L, -H). The maxillofacial region of the patient is fixed with a surgical holder so that the patient's open oral cavity does not move during surgery.

As a relative initial position of both coordinate systems, the XZ plane of the C1 system and the XZ plane of the Cm system are directed to face each other, the tip of the handpiece is brought close to the magnet, and the initial position of the tip of the handpiece is set. The grid system on the handpiece in this state was designated as the C1 system.

Next, in that state, the grid is used to calculate the position R1 and the orientation (θ, φ) of the magnet in the coordinate system C1. By rotating the Y axis by θ degrees and rotating the Y axis by −φ degrees, the azimuth relationship between both coordinate systems was matched. The handpiece system in this state was designated as C2 system.
Viewed from the C2 system, A2B2=OmB2+R2-OhA2. Here, since the orientations of the C2 system and the Cm system match, OmB2=OmB1, and OhA2 is the same as OhA1 since it is a vector quantity of the C system. Since R2 is a vector quantity obtained by the C1 system, R2=Ry(φ1)Rz(θ1)R1 corresponding to the rotation of the coordinate system.

Since the relative position and azimuth relationship between the two systems have been grasped, an approach path toward the treatment position is selected on the three-dimensional X-ray image, and the tip A of the handpiece is moved to the treatment position along that path. Move to B. The most basic path is to move the tip position A of the handpiece straight to the treatment site B. The angle α on the horizontal plane between R2 and A2B2 is obtained from the inner product of both vectors. Next, rotate the Z-axis about the rotation axis by α degrees, direct the Y-axis to the point B2, and assume this state as the C3 system.
In the C3 system, the grid is used to calculate the position R3 and orientation (θ ₃ , φ ₃ ) of the magnet, A3B3=OmB3+R3-OhA3. Here, OmB3=R(-α)OmB2 is obtained. OhA3 does not change because it is a C-system vector.

From the angle between A3B3 and the Z-axis (0, 0, 1), the tilt angle β of the Y-axis is obtained, the C3 system is rotated by β degrees about the rotation axis of the X-axis, and the Z-axis is directed toward the point B, This state is called C4 system.
In the C4 system, using the grid, calculate the position R4 and orientation (θ ₄ , φ ₄ ) of the magnet to obtain A4B4=OmB4+R4-OhA. where OmB4=R(-β)OmB3.

Since the direction and distance of the approach path are determined, the tip position A of the handpiece is moved to the treatment position B along the path, and the coordinate system at that time is defined as the C5 system. In the C5 system, use the grid to calculate the position R5 and orientation (θ ₅ , φ ₅ ) of the magnet and confirm that R5≈0.

Drill holes for implant placement. The direction of drilling is Ex degrees with the X axis as the rotation axis and Ey degrees with the Y axis as the rotation axis. ) degrees and horizontally moved by (Ex−B)×h in the Y-axis direction. Next, the Y-axis is rotated by Ey degrees around the rotation axis, and horizontally moved by Ey×h in the X-axis direction. This state is referred to as C6 system. In the C6 system, using the grid, calculate the position R6 and the orientation (θ ₆ , φ ₆ ) of the magnet and confirm that R6≈0.

After confirming the orientation and position of the handpiece, the drill is rotated and the handpiece is moved by a distance D to form the C7 system. In the C7 system, use the grid to calculate the position R7 and orientation (θ ₆ , φ ₆ ) of the magnet and confirm R7−R6≈D.
After confirmation, return the handpiece to the initial position in the reverse route of the approach path. The handpiece can be guided in the manner described above.

The sixth problem is to fix the patient's maxillofacial area with a fixing holder, but to prevent the patient from moving while the handpiece is being guided, the position and orientation of the patient should be measured at all times. If there is a difference of 1 mm or more from the amount of change that can be calculated from the amount of movement in , the movement is temporarily stopped, the state is set as the C1 system, and the above guidance operation is resumed, and the position accuracy is 0.1 mm or less and the azimuth accuracy is 1 degree or less. Secure.

Alternatively, the angle between the CCD camera system Ca and the intraoral dentition system Cb is initially set by the CCD camera, and the patient's maxillofacial region moves to move the dentition system Cb relative to the Ca system. When a change of 1 mm or more is confirmed, the movement is temporarily stopped, and the guidance operation is restarted as the C1 system in that state to ensure the position accuracy of 0.1 mm or less and the azimuth accuracy of 1 degree or less.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to measure the precise position and orientation of a handpiece in the oral cavity in dental treatment, and to accurately guide the handpiece, thereby realizing robotization of implant treatment. It is expected that

2 is a plan view of a GSR element; FIG. Fig. 3 is an electronic circuit diagram for a GSR sensor; FIG. 3 is a plan view of a magnetic field vector sensor (integrated type) using a GSR sensor; FIG. 10 is a cross-sectional view of a magnetic field vector sensor (integrated type) using a GSR sensor taken along line A1-A2; FIG. 10 is a plan view of a magnetic field vector sensor (assembled type) using a GSR sensor; FIG. 10 is a cross-sectional view of a magnetic field vector sensor (assembled type) using a GSR sensor taken along line B1-B2; Fig. 10 is a perspective view of a cylindrical grid sensor installed at the tip of the handpiece; Fig. 10 is a perspective view of a grid plate type distribution grid sensor installed at the distal end of the handpiece; It is a figure which shows the flowchart of a calculation program. (a) shows the influence of the magnetic moment of the magnet on the positional accuracy, and (b) shows the influence of the magnetic moment on the azimuth accuracy. FIG. 10 is a diagram showing a flow chart of a guidance program; 1 is a conceptual diagram of a guidance system for a handpiece; FIG. It is a figure which shows the coordinate C1 system of the initial state in a guidance system. FIG. 4 is a diagram showing a coordinate system C3 in the guidance system in a movement start state; FIG. 11 shows the coordinate C4 system of the treatment position (B4) state in the guidance system;

A first embodiment of the present invention is as follows.
A magnet is attached to a tooth, and the position/direction detection device of the handpiece attaches one magnet to a specific tooth in the oral cavity so that the length direction of the magnet marker is perpendicular (Z-axis), and the magnetization vector is A coordinate system installed in the horizontal direction (X-axis), with the center of the magnet as the origin Om, the direction of the magnetization vector as the X-axis, the thickness direction of the magnet as the Y-axis, and the longitudinal direction as the Z-axis. Cm, the center point of the treatment position in the oral cavity is defined as point B (hereinafter referred to as treatment position B), and the positional relationship from the center of the magnetic marker is defined as OmB,
The handpiece has a magnetic field vector sensor grid consisting of a three-axis acceleration sensor and a magnetic field vector sensor in its main body,
The three-axis acceleration sensor is installed in the body of the handpiece, has a function of measuring an inclination angle η of the handpiece with respect to a horizontal plane, and transfers the measured value to the data processing device,

The magnetic field vector sensor grid is installed near the tip of the handpiece on the patient's oral cavity side, the center of the magnetic field vector sensor grid is the origin Oh, the axis of the handpiece is the Y axis, and the grid of the magnetic field vector sensor grid is It has a coordinate system C with the horizontal direction of the plate as the X axis and the vertical direction of the grid plate as the Z axis, and has a function of measuring the magnetic field emitted by the magnet and transferring the measured data to the sensor data processing device. ,
Furthermore , the tip position of the drill of the handpiece is defined as point A (hereinafter referred to as tip position A), the coordinate system is set to C, and the positional relationship from the center of the grid is defined as OhA,
The sensor data processing device integrally processes the measured values detected by the three-axis acceleration sensor and the magnetic field vector sensor grid and the fixed values of OmB and OhA to determine the treatment position in the cavity and the tip of the handpiece. It consists of a display device that has a function to calculate the position and orientation relationship and informs the operator of those values,

The sensor data processor calculates the positions X, Y, Z and the orientations θ, φ of the magnetic marker by the C system using the magnetic field vector sensor grid measurements, and also calculates the acceleration sensor measurements. to calculate the azimuth η, the azimuth relationship between the C system and the Cm system and the distance between the origins; It is characterized by calculating the position/orientation relationship of the tip of the piece and notifying the operator of it.

Each component will be specifically described below.
<Magnet body>
The magnetic body is a pulse-type electromagnet, an AC-type electromagnet, or a permanent magnet, the size width is 4 mm or less, the length is 10 mm or less, and the magnetic moment of the magnetic body marker is 5×10 ⁻⁹ to 100×10 ⁻⁹ Wbm. do. The magnetic marker must be small enough to be placed on the tooth, but if it is small, the magnetic moment will be small, the generated magnetic field will be weak, and the positioning accuracy will be lowered.

The pulse magnetic field type electromagnet has a pulse period of 50 Hz to 1 kHz and a pulse width of 0.1 seconds to 5 ms. The excitation current I has a strength that can saturate the magnetic needle material, that is, a current strength that takes into consideration the number of coil turns so that the magnetizing force H is five times or more the coercive force Hc.

The AC electromagnet is a coil wound around a magnetic body, and has a frequency of 10 Hz to 10 kHz. The excitation current I is set to a range of magnetizing force that can linearly magnetize the magnetic needle material, approximately 0.5 times or less than the coercive force Hc, and the number of coil turns is taken into account so that the magnetizing force H is H<0.5Hc. be the current intensity.

When a permanent magnet is used, it is easily affected by a surrounding magnetic field, so a magnet body marker having as large a magnetic moment as possible, for example, about 20×10 ⁻⁹ to 100×10 ⁻⁹ Wbm is used. For this purpose, a rare earth magnet having a BHmax of 30MGOe to 55MGOe is used after being subjected to antirust treatment. Although the present invention is not limited to a specific magnet material, it is preferable to use magnets with as large a magnetic force as possible.

<Magnetic field vector sensor>
The GSR sensor repeatedly and rapidly measures the magnetic field with a pulse period of 1 MHz to 5 MHz, averages it, and outputs it at a measurement rate of 200 Hz to 1 KHz.
Magnetic field vector sensors using GSR sensors include an integrated type (Figs. 3 and 4) in which a 3D GSR element is directly formed on the ASIC surface, and an On-ASIC type GSR sensor (size: 2 mm long, 1 mm wide). ) are attached to the four slopes of the ridge of the truncated square pyramid in four-fold symmetry and mirror symmetry (FIGS. 5 and 6).

The integrated type has a detection power of 50 nT or less at a measurement speed of 1 kHz, and the size ranges from 1.2 mm wide x 1.2 mm long x 1 mm high to about 2 mm wide x 2 mm long x 2 mm high. be.
The assembly-type type sensor has a measurement speed of 5 nT or less at 1 kHz, and is an assembly-type magnetic field vector sensor that is ultra-compact with a size of width 5 mm×length 5 mm×height 2 mm or less and excellent in magnetic field detection capability.
The present invention uses small, high performance magnetic field vector sensors and is not limited to the above two types of use.

Since the magnetic field vector sensor simultaneously measures the magnetic field emitted from the magnet body and the surrounding magnetic field, the influence of the surrounding magnetic field is eliminated from the measured value and only the magnetic field emitted from the magnet body is detected and used.
In the case of the pulse magnetic field type electromagnet and the AC type electromagnet, the variation width of the detected magnetic field was taken as the magnetic field emitted from the magnet body marker. In the case of permanent magnets, the peripheral magnetic field is measured in advance and corrected by subtracting the value from the measured value.

<Magnetic field vector sensor grid>
Magnetic field vector sensor grids are highly spatially and geometrically constrained due to the intraoral insertion of the handpiece.
The magnetic field vector sensor grid has magnetic field vector sensors geometrically attached to the tip of the handpiece, and five or more magnetic field vector sensors are arranged on the sensor grid body at magnetic field vector sensor intervals of 3 to 25 mm. The center of the grid is the origin, the direction of the handpiece axis is the Y axis, the lateral direction (horizontal direction) of the sensor grid is the X axis, and the vertical direction (vertical direction) of the sensor grid plate is the Z axis. and

In the first embodiment, the nine magnetic field vector sensors shown in FIG. 7 are geometrically arranged on the cylindrical portion at the tip of the handpiece, and this is used as a grid body.
The magnetic field vector sensor grid connects each magnetic field vector sensor with a multiplexer MUX and all subsequent data is connected with the final MUX and forwarded to external signal processing circuitry. Although not shown, power supply wiring VDD and ground wiring GND are connected to each magnetic field vector sensor so that power can be supplied to all magnetic field vector sensors when the sensor grid is in operation. The grid electronic circuit board is preferably mounted on the handpiece body.
The assembly accuracy of the sensor grid is required to be as small as possible, and an error of 10 μm or less is preferable.

<Measurement by magnetic field vector sensor grid>
For the measurement of the magnetic marker by the magnetic field vector sensor grid, a coordinate system with the center of the grid as the origin, the handpiece axis as the Y axis, the horizontal direction of the grid plate as the X axis, and the vertical direction of the grid plate as the Z axis. A C system is used, an acceleration sensor is installed on the handpiece, the Y axis is kept horizontal, and the XZ plane, which is the grid sensor plane, is kept vertical.
The initial position of the handpiece is such that the XZ plane of the C system of the handpiece and the XZ plane of the Cm system of the magnet face each other. The tip will be guided to the designated treatment position in the oral cavity. In this process, the position and orientation relationship between the tip of the handpiece and the magnet is measured by the magnetic field vector sensor grid, and the data is transferred to the sensor grid data processing circuit, where the measurement data measured by the magnetic field vector sensor grid is processed at high speed. do.

<Calculation in data processor>
The data processor calculates the position and orientation of the magnetic marker using the grid-based measurement of the magnetic marker. The position (X, Y, Z) and orientations Θ and Φ of the magnet are calculated from the origin of the C coordinate system by the Gauss-Newton method.

The calculation method is as shown in FIG. 9. Let (X, Y, Z) be the position of the magnet ( ) in the C coordinate system, let The position and orientation (X, Y, Z, Θ and Φ) of the magnet body, with the rotation angle Φ, according to the Gauss-Newton method,

(1) Measure the magnetic field vector _m H (→) _ij at the position (i, j) of each magnetic field vector sensor of the magnetic field sensor grid fixed to the C coordinate system (step 101),
(2) Confirm that the absolute value is 500 times or more in S/N ratio (step 102),
(3) Assuming that the magnet ( ) is at a position (x, y, z) and an orientation (θ, φ) with respect to the C coordinate system, the magnetic field vector created by the position (i, j) of the magnetic field sensor grid
Calculate the theoretical value of _t H(→) _ij (step 103);
(4) calculating the measurement error by e _ij = _t H(→) _{ij −m} H(→) _ij (step 104);
(5) calculating the sum of squares of the errors by E _ij =Σe _ij ² (step 105);
(6) Calculate x, y, z, θ, and φ that minimize the error sum of squares (step 106)
(7) Find the positions X, Y, Z of the magnet and the orientations Θ, Φ (step 107),
Positional accuracy of 0.5mm or less, azimuth accuracy of 1 degree or less, measurement sampling rate of 1 to 50H
In this method, the position and orientation are measured at z, and the data are calculated at a rate of 1 Hz to 50 Hz. By this method, the position and orientation of the magnet in the Ch system can be measured with a sensor grid with a position accuracy of 0.1 mm or less and an orientation accuracy of 1 degree or less.

A second embodiment of the present invention is a method for guiding the tip position A of the handpiece to the treatment position B using the first embodiment, and will be described with reference to FIG.
First, from a three-dimensional X-ray CT image map, the position of the magnetic body marker in the oral cavity is specified, and Cm with the center point Om of the magnetic body marker and the direction of magnetization as the X axis and the vertical direction of the magnet body as the Z axis. Assuming a system, specify the location and orientation of treatment location B.
Next, the sensor grid measures the position and orientation of the magnet in the C system, and using the measured values of the orientation θ and φ of the magnet, the C system is rotated by −θ with the Z axis of the C system as the rotation axis. , the angle deviation of the XY plane of both systems can be corrected, and the angle deviation of the ZX plane can be corrected by -φ rotation of the C system about the Y axis as the rotation axis, so that the orientations of both systems can be matched.
A vector AB in the C system can be obtained by transforming the coordinate point of the treatment position B in the Cm system in the C system after rotation to that in the C system. This vector AB can specify the relative position-orientation relationship between the tip position A and the treatment position B of the handpiece.

<Guidance system>
A guidance system in which a handpiece using this method is gripped by a robot hand of an automatic control device to treat teeth is carried out according to the procedure shown in FIG.
(1) In advance, the coordinate position of the tip position A of the handpiece in the handpiece C system, the coordinate position of the treatment position B in the intraoral magnet system Cm, and the direction of drilling are rotated by β angle about the Y axis as the rotation axis, Next, input the γ angle rotation and the depth H of the hole with the X axis as the rotation axis, keep the Y axis of the handpiece horizontal, hold it near the magnet installed on the tooth, and induce that state. As the initial position of the system, the coordinate system C in this state is defined as C1 (FIG. 13), the magnetic field emitted from the magnet body is measured by the magnetic field vector by the sensor grid, and the position (x, y, z) and orientation of the magnet body (θ, φ) is calculated (step 201).

(2) Rotate the direction of the handpiece by -θ about the Z axis, change the coordinate system C in this state to the C2 system, and calculate the angle α between the treatment position B and the Y axis (step 202).

(3) Rotate the Z-axis of the handpiece at an angle α around the rotation axis to orient the handpiece in the treatment position B direction. After that, in order to orient the drill in the direction of drilling, the drill is rotated by β angle around the Y axis, and then rotated by γ angle around the X axis. ,
The position (x, y, z) and orientation (θ, φ) of the magnet are calculated to calculate the positional relationship AB between the tip position A of the handpiece and the predetermined treatment position B (step 203).

(4) Move the tip position A of the handpiece along the Y-axis, guide it to a predetermined treatment position B, and stop it.
The position (x, y, z) and orientation (θ, φ) of the magnet body were calculated, and the positional relationship AB between the tip position A of the handpiece and the predetermined treatment position B was calculated. The azimuth deviation is 1 mm or less and 1 degree or less, and it is confirmed that the two match (step 204).

(5) If the two do not match, each axis is finely moved to correct the positional deviation so that it is 0.1 mm or less, and each axis is finely rotated about the rotation axis so that the azimuth deviation is 1. The coordinate system C in this state is changed to the C5 system (step 205).

(6) Move the handpiece in the specified direction by the specified distance H to complete the treatment, and let the coordinate system C in this state be the C6 system,
Calculate the position (x, y, z) and orientation (θ, φ) of the magnet body, and confirm that the tip position A of the handpiece is at the depth H in the direction of the specified hole (step 206).

(7) Return the handpiece by H along the Z-axis of the C6 system, then move the distance AB along the Y-axis as it is by the distance vector between origins (-X, -Y, -Z), and By returning to the position of point A, the implant hole drilling can be performed under automatic control (step 207).

Although the patient's maxillofacial region is fixed with a fixed holder while the handpiece is being guided, the following countermeasures should be prepared in advance if the patient moves.
Always measure the position and orientation of the handpiece, and if there is a difference of 1 mm or more from the amount of change that can be calculated from the amount of movement of the handpiece, temporarily stop the movement of the handpiece, and use that state as the C1 system, and perform the above guidance operation. shall be resumed, and a positional accuracy of 0.1 mm or less and an azimuth accuracy of 1 degree or less shall be secured.

Alternatively, the angle between the CCD camera system Ca and the intraoral dentition system Cb is initially set by the CCD camera, and the patient's maxillofacial region moves to move the dentition system Cb relative to the Ca system. If a change of 1 mm or more can be confirmed, the movement shall be temporarily stopped, the state shall be regarded as C1 system, and the above guidance operation shall be resumed to ensure the position accuracy of 0.1 mm or less and the azimuth accuracy of 1 degree or less. .

<Guidance assistance system to the operator>
The third embodiment of the present invention utilizes the second embodiment to provide a system in which the operator holds the handpiece by hand instead of the automatic control device and assists the operator.
(1) The operator memorizes the input values specified on the display screen, the positions of points A and B, the direction of drilling and the depth H of the hole,
Hold the tip of the handpiece horizontally and close to the magnet installed on the tooth. In this state, calculate the position (x, y, z) and orientation (θ, φ) of the magnet body, and the initial position of the guidance system. , the value is conveyed to the operator to assist, and the coordinate system C in this state is set to C1 (step 301).

(2) When rotating the direction of the handpiece by -θ around the Z axis, the operator is assisted by conveying the change in rotation angle during rotation to the operator, and when the amount of rotation reaches θ, the handpiece stops and this state is restored. The coordinate system C is defined as the C2 system, and the angle α between the treatment position B and the Y axis is calculated (step 302).

(3) The operator rotates the handpiece through an α angle around the Z axis of the handpiece, and orients the handpiece in the treatment position B direction. After that, in order to orient the drill in the direction of drilling, the Y axis is rotated by an angle of β, and then the X axis is rotated by an angle of γ. , the operator is assisted by conveying the change in rotation angle to the operator, and stops when a predetermined amount of rotation is reached. , z) and the orientation (θ, φ) are calculated, and the positional relationship AB between the tip position A of the handpiece and the predetermined treatment position B is calculated (step 303).

(4) The operator moves the tip position A of the handpiece to a predetermined treatment position B along the Y-axis. When moving, the position (x, y, z) and orientation (θ, φ) of the magnet are calculated, the positional relationship between the tip position A of the handpiece and the predetermined treatment position B is calculated, and the amount of movement is conveyed to the operator to assist, and the coordinate system C in this state is assumed to be the C4 system, and the positional deviation between the two is 0.1 mm or less and the azimuth deviation is 1 degree or less. is confirmed (step 304).

(5) If the positional deviation between the two is 0.1 mm or less and the azimuth deviation is not 1 degree or less, the operator finely moves each axis to correct the positional deviation to 0.1 mm or less. is slightly rotated about the rotation axis to correct the azimuth deviation to 1 degree or less. The correction result is communicated to the operator for assistance, and the coordinate system C in this state is changed to the C5 system (step 305).

(6) When the handpiece is moved in a specified direction by a specified distance H, the amount of movement during movement is communicated to the operator, and when the specified value H is reached, the operator can finish processing. , and let the coordinate system C in this state be the C6 system.
The position (x, y, z) and orientation (θ, φ) of the magnet are calculated, and it is confirmed that the tip position A of the handpiece is at the depth H in the direction of the hole (step 306).

(7) The operator returns the handpiece by H along the Z-axis of the C6 system, and then moves the distance AB along the Y-axis by the distance vector between origins (-X, -Y, -Z). In the operation to return to the position of point A of the C4 system, the operator is informed of the movement distance during the operation (step 307),
A handpiece guidance assist system characterized by assisting implant drilling.

In the fourth embodiment of the present invention, in the second embodiment,
Instead of placing a grid on the cylindrical portion of the tip of the handpiece, a grid plate is placed on the tip of the handpiece, and a grid (Fig. 7) is used in which 12 vector sensors are placed on the grid plate. , and is the same as the second embodiment except for the shape of the grid.

[Example 1]
Based on the magnetic field vector sensor grid used in the first embodiment, a pulse-type electromagnet is used as the magnet body, and an integrated type consisting of a three-dimensional element and an ASIC is used as the magnetic field vector sensor.

The magnet body is a pulse-type ^{electromagnet} with a size width of 4 mm, a length of 5 mm, and a thickness of 1 mm. did. Permalloy having a magnetic permeability of 30,000 and a coercive force of 80 A/m was used as the magnetic material of the magnetic needle. The number of turns of the coil was 400 times, 100 times per 1 mm, the exciting current was 0.5 A, the magnetizing force H was 200 A/m, and the magnetic needle was saturated.

As a countermeasure against peripheral magnetic field noise, the magnetic field vector sensor detects an oscillating magnetic field corresponding to the strength _Hm of the magnetic field generated by the magnet around the peripheral magnetic field. A magnetic field vector generated from the magnet body is half of the average amplitude of the vibration. Moreover, it was confirmed that there is no influence of environmental fluctuations of the surrounding magnetic field, especially fluctuations of the magnetic field _H0 caused by movement of the handpiece.

Since the magnetic field vector sensor is attached on the cylinder at the tip of the handpiece, we adopted an integrated type, giving priority to its small size. Its performance has a power of 50 nT at a measurement rate of 1 kHz and a size of 1.2 mm x 1.2 mm x 1 mm height.

As shown in Fig. 7, the magnetic field vector sensor grid has 9 sensors arranged in a cylindrical shape on the cylindrical part of the tip of the handpiece. I attached three.
The center of the grid is the center of the plane on which the six sensors are arranged. system.

The method shown in FIG. 9 was used in the first embodiment as a program for calculating the position and orientation of the magnet. As a result, the position and orientation of the magnet body were measured within a distance of 5 mm to 50 mm from the origin of the handpiece system, at a measurement speed of 20 Hz, the position accuracy was 0.1 mm or less, and the azimuth accuracy was It could be obtained at 0.7 degrees or less.

[Example 2]
This is a system for guiding the distal end of a handpiece to a treatment position in the oral cavity using the magnet position/orientation detection device of the first embodiment.
As for the initial position of the handpiece, the acceleration sensor is installed on the handpiece, the Y axis is kept horizontal, and the XZ plane, which is the grid sensor plane, is kept vertical. With the C-based XZ plane of the handpiece and the Cm-based XZ plane of the magnet facing each other, the handpiece is brought closer to the oral cavity along the Y-axis, and the initial position of the handpiece is set as close as possible. It was determined.

The sensor grid detected the magnetic field generated by the magnet and transferred the data to the sensor grid data processing circuit. The sensor grid data processing circuit processes measurement data measured by the magnetic field sensor grid at high speed. Φ was calculated by the Gauss-Newton method for the position and orientation of the magnet body in the C system. Here, .theta. is the angular deviation of the XY planes of both systems, which can be matched by Z-axis rotation. φ is an angular deviation of the ZX plane and can be matched by Y-axis rotation.
Using that value, we decided to guide the tip of the handpiece to the designated treatment site in the oral cavity.

As a result of guiding the handpiece according to the flow chart shown in FIG. 12, the tip of the handpiece could be guided with a positional accuracy of 0.1 mm or less and an azimuth accuracy of 0.7 degrees or less.

[Example 3]
In Example 2, an AC electromagnet is used as the magnet.
The magnet was an ^AC electromagnet with a width of 4 mm, a length of 5 mm, and a thickness of 1 mm. Permalloy with magnetic permeability of 30,000 and coercive force of 80 A/m is used as the magnetic material of the magnetic needle. m, and the linear region of the permalloy BH curve was utilized.

As a countermeasure against peripheral magnetic field noise, the magnetic field vector sensor detects an oscillating magnetic field corresponding to the magnetic field strength H _m generated by the magnetic marker around the peripheral magnetic field. A half of the average of the vibrating amplitude becomes the magnetic field vector emitted from the magnetic marker. Moreover, it has been confirmed that there is no influence of environmental changes in the surrounding magnetic field, especially changes in the magnetic field _H0 due to movement of the handpiece.

The program for calculating the position and orientation of the magnet was the same as the method shown in FIG. 9 used in the first embodiment. As a result, the position and orientation of the magnet were measured at a speed of 20 Hz within a distance of 5 mm to 50 mm from the origin of the handpiece system. Accuracy could be obtained at 0.7 degrees or less.
As a result of guiding the handpiece according to the flow chart shown in FIG. 12, the tip of the handpiece could be guided with a positional accuracy of 0.1 mm or less and an azimuth accuracy of 0.7 degrees or less.

[Example 4]
In Example 2, an NdFeB magnet was used as a permanent magnet that is a permanent magnet made from a pulse-type electromagnet. As a countermeasure against peripheral magnetic field noise, the peripheral magnetic field was measured at both the initial position of the handpiece and the treatment position. The patient was then fixed in place during surgery and the handpiece's grid sensor was used to measure the magnetic field from magnets placed on the patient's teeth. Using the difference between the two as a measurement of the magnetic field from the magnet, we decided to determine the position of the handpiece from the position at the initial position and the treatment position. At this time, it is preferable to use a handpiece using a non-magnetic material.
As a result, the tip of the handpiece could be guided with a positional accuracy of 0.1 mm or less and an azimuth accuracy of 0.7 degrees or less.

[Example 5]
In Example 2, as the magnetic field vector sensor, a prefabricated type is used, and a grid is used in which a grid plate is arranged at the tip of the handpiece and 12 magnetic field vector sensors are arranged there.

The assembly type magnetic field vector sensor has a detection power of 5 nT or less at a measurement speed of 1 kHz, and is an ultra-compact magnetic field vector sensor with a size of 5 mm (width) x 5 mm (length) x 2 mm (height) and excellent in magnetic field detection power. . In the method of attaching to the grid plate, the distance from the magnet becomes larger than in the case of installing in the cylindrical portion at the tip. Therefore, we decided to use a magnetic field vector sensor with higher detection power.

The magnetic field vector sensor grid is a transparent sensor grid plate attached to the handpiece, with a width of 60 mm and a length of 45 mm. , and placed one sensor on the handpiece shaft (Fig. 7). The sensor grid substrate is connected with multiplexer MUX column by column, then all data is connected with the final MUX and transferred to the external signal processing circuit. The power wiring system provides power to all sensors for sensor grid operation. The assembly accuracy of the sensor grid was set to 10 μm or less.

The program for calculating the position and orientation of the magnet was the same as the method shown in FIG. 9 used in the first embodiment. As a result, the position and orientation of the magnet marker were measured at a measurement speed of 20 Hz within a distance range of 5 mm to 50 mm from the origin of the handpiece system, the position accuracy was 0.1 mm or less, and the orientation accuracy was It could be obtained at 0.7 degrees or less.
As a result of guiding the handpiece according to the flow chart shown in FIG. 12, the tip of the handpiece could be guided with a positional accuracy of 0.1 mm or less and an azimuth accuracy of 0.7 degrees or less.

Although the patient's maxillofacial region is fixed with a fixed holder while the handpiece is being guided, the patient may move, so the following countermeasures should be prepared in advance.
Always measure the position and orientation of the handpiece, and if there is a difference of 1 mm or more from the amount of change that can be calculated from the amount of movement of the handpiece, temporarily stop the movement of the handpiece, and use that state as the C1 system, and perform the above guidance operation. shall be resumed to ensure a positional accuracy of 0.1 mm or less and an azimuth accuracy of 1 degree or less.

Alternatively, the angle between the CCD camera system Ca and the intraoral dentition system Cb is initially set by the CCD camera, and the patient's maxillofacial region moves to move the dentition system Cb relative to the Ca system. If a change of 1 mm or more can be confirmed, the movement shall be temporarily stopped, the state shall be regarded as C1 system, and the above guidance operation shall be resumed to ensure the position accuracy of 0.1 mm or less and the azimuth accuracy of 1 degree or less. .

According to the present invention, it is possible to automatically guide the treatment handpiece for hole processing of the jawbone necessary for implant processing in the oral cavity, and implant treatment can be performed more safely and accurately. expected to be

1: GSR element 11: substrate 12: magnetic wire 13: coil 14: wire terminal 15: wire electrode 16: connection wiring (for wire electrode) 17: coil terminal 18: coil electrode 19: connection Wiring (for coil electrodes)
2: Electronic circuit (electronic circuit of GSR sensor)
21: pulse oscillator, 22: GSR element, 221: wire electrode, 222: coil electrode, 23: parasitic capacitance, 24: circuit input electrode, 25a: first stage detection timing adjustment circuit (T1), 25b: second stage detection Timing adjustment circuit (T2), 26: sample and hold circuit (output side circuit), 27a: 1st stage electronic switch (SW1), 27b: 2nd stage electronic switch (SW2), 28a: 1st stage sample and hold capacitor ( C1), 28b: second-stage sample-and-hold capacitor (C2), 29: amplifier 3: magnetic field vector sensor (integrated type)
31: ASIC, 32: magnetic wire, 33: wire electrode, 34: coil electrode, 35: upper soft magnetic body, 36: lower soft magnetic body, 37: resist layer (photosensitive resin), 38: connection electrode hole, 391: magnetism collection (discharge), 392: magnetism discharge (collection), X1: X1-axis element, X2: X2-axis element, Y1: Y1-axis element, Y2: Y2-axis element 4: Magnetic field vector sensor (assembly type)
40: pedestal (frustum of square pyramid), 401: slope of triangle, 402: slope of rectangle (ridge of square pyramid), 403: upper surface of square, 404: angle of inclination (θs), 41: GSR sensor (on- ASIC type), 411: ASIC, 412: GSR element, 413: magnetic wire 5: hand piece (cylindrical part type)
50: cylindrical portion, 51: magnetic field vector sensor, 52: drill tip, Oh: origin 6: handpiece (axis grid plate type)
60: shaft, 61: magnetic field vector sensor grid, 62: grid plate (installed on shaft), 63: magnetic field vector sensor, 64: drill, 65: acceleration sensor, Oh: origin 7: three-dimensional X image map 71: hand piece, 710: origin of handpiece Oh, 711: positional relationship OhA
72: magnet body (pulse-type electromagnet), 720: origin Om of magnet body, 721: direction of magnetization (X-axis), 722: positional relationship OmB
73: bone 74: tooth A: tip position of handpiece
B: treatment position 8: coordinate system C in the guidance system
801: Magnetic field vector sensor (sensors that make up the magnetic field vector sensor grid)
81: handpiece, 8101: C1 system origin Oh1, 8103: C3 system origin Oh3, 8104: C4 system origin Oh4
82: magnet, 820: origin Om of magnet, 821: angle θ, 822: α rotation angle 83: tooth C1: initial state coordinate system, C3: handpiece movement start state coordinate system, C4: handpiece Coordinate system R1: position of the magnet in the C1 system, R3: position of the magnet in the C3 system, R4: position of the magnet in the C4 system when the treatment position is reached.

The calculation method is as shown in FIG. 9, where the position of the magnet (M(→)) in the C coordinate system is (X, Y, Z), and the orientation of the magnetization vector is θ as the rotation angle with respect to the X axis. , the rotation angle with respect to the Z axis is Φ, and the position and orientation (X, Y, Z, Θ and Φ) of the magnet are calculated according to the Gauss-Newton method as follows:

(1) measuring the magnetic field vector _m H (→) _ij at the position (i, j) of each magnetic field vector sensor of the magnetic field sensor grid fixed to the C coordinate system (step 101);
(2) Confirm that the absolute value is 500 times or more in S/N ratio (step 102),
(3) Assuming that the magnet (M (→)) is at the position (x, y, z) and the orientation (θ, φ) with respect to the C coordinate system, the position (i, j) of the magnetic field sensor grid The magnetic field vector produced by
Calculate the theoretical value of _t H(→) _ij (step 103);
(4) calculating the measurement error by e _ij = _t H(→) _{ij −m} H(→) _ij (step 104);
(5) calculating the sum of squares of the errors by E _ij =Σe _ij ² (step 105);
(6) Calculate x, y, z, θ, and φ that minimize the error sum of squares (step 106)
(7) Find the positions X, Y, Z of the magnet and the orientations Θ, Φ (step 107),
Positional accuracy of 0.5mm or less, azimuth accuracy of 1 degree or less, measurement sampling rate of 1 to 50H
In this method, the position and orientation are measured at z, and the data are calculated at a rate of 1 Hz to 50 Hz. By this method, the position and orientation of the magnet in the Ch system can be measured with a sensor grid with a position accuracy of 0.1 mm or less and an orientation accuracy of 1 degree or less.

Claims (9)

In the position and direction detection device for the tip of the handpiece used for intraoral treatment with the magnet attached to the tooth as the origin,
The magnet body is installed on a specific tooth in the oral cavity with the length direction of the magnet body in the vertical direction (Z-axis) and the magnetization vector in the horizontal direction (X-axis), A magnetic coordinate system Cm system (hereinafter referred to as Cm system) having the center of the magnet as the origin Om, the direction of the magnetization vector as the X axis, the thickness direction of the magnet as the Y axis, and the longitudinal direction as the Z axis, With the treatment position of as point B, the positional relationship from the origin Om of the magnet is defined as OmB,
The handpiece comprises a magnetic field vector sensor grid consisting of a 3-axis acceleration sensor and a magnetic field vector sensor,
The three-axis acceleration sensor is installed in the main body of the handpiece, measures an inclination angle η of the handpiece with respect to a horizontal plane, and transfers the measured value to a sensor data processing device;
The magnetic field vector sensor grid is installed near the tip of the handpiece on the oral cavity side of the patient. A grid coordinate system C (hereinafter referred to as C system) in which the horizontal direction of the plate is the X axis and the vertical direction of the grid plate is the Z axis, the magnetic field generated by the magnet is measured, and the measured value is used as the sensor data. transfer to processing equipment;
Further, with the tip of the handpiece as point A, the positional relationship from the grid origin Oh is defined as OhA,
The sensor data processing device integrally processes the measured values of the three-axis acceleration sensor, the measured values of the magnetic field vector sensor grid, the OmB of the Cm system and the OhA of the C system, Equipped with a display device that calculates the position and orientation relationship between the treatment position B and the tip of the handpiece and notifies the operator of these values,
The sensor data processor also uses the magnetic field vector sensor grid measurements to calculate the positions X, Y, Z and orientations .THETA., .PHI. is used to calculate the tilt angle η, the azimuth relationship between the C system and the Cm system and the distance between the origins, and the coordinate transformation of the Cm system data OmB to the C system. A position/orientation detection device for the distal end of a handpiece, which calculates the position/orientation relationship between the treatment position B and the distal end A of the handpiece, and informs the operator of the position/orientation. In claim 1,
The magnet body is an AC electromagnet, a pulse electromagnet or a permanent magnet,
The size of the magnet is 6 mm or less in width and 10 mm or less in length,
A position/orientation detecting device for a distal end of a handpiece, characterized in that the magnetic moment of the magnet body is 5×10 ⁻⁹ to 100×10 ⁻⁹ Wbm. In claim 1 or 2,
The magnetic field vector sensor is composed of four magnetic field sensor elements arranged two each in the X-axis direction and two Y-axis directions, and a soft magnetic material for collecting and releasing the magnetic field in the Z-axis direction. Calculate the magnetic fields Hx1, Hx2, Hy1, Hy2 detected by using an electronic circuit and an arithmetic circuit using the formulas Hx = (Hx1 + Hx2) / 2, Hy = (Hy1 + Hy2) / 2, Hz = (Hx1 + Hx2 + Hy1 + Hy2) / 4 and integrally measure the magnetic field vector (Hx, Hy, Hz) at the center of the four magnetic field sensors,
The size is 2 mm to 6 mm at the base and 0.5 mm to 2 mm in height. ). In claim 1 or 2,
The magnetic field vector sensor elements are four On-ASIC type GSR sensors in which a uniaxial GSR element is formed on the top surface of the ASIC, and are attached to four slopes of a truncated square pyramid with an inclination angle θ in a four-fold symmetrical and mirror symmetrical manner. , measuring the output voltages Vx1, Vx2, Vy1, Vy2 of the four sensors,
Hx = (1/2 cos θ) (Hx1-Hx2),
Hy = (1/2 cos θ) (Hy1-Hy2),
Hz = (1/4 sin θ) (Hx1 + Hx2 + Hy1 + Hy2),
is an assembly type that measures the magnetic field vector (Hx, Hy, Hz) at the center of the four magnetic field sensors,
The size is 2 mm to 6 mm in length, 1 mm to 2 mm in height, and the angle of inclination θ is 20 degrees to 45 degrees. (Hx, Hy, Hz). In any one of claims 1 to 3,
The magnetic field vector sensor grid comprises magnetic field vector sensors geometrically attached to the distal end of the handpiece,
5 or more of the magnetic field vector sensors are arranged on the magnetic field vector sensor grid body with a magnetic field sensor interval of 3 to 25 mm,
The center of the magnetic field vector sensor grid is the origin, the direction of the handpiece axis is the Y axis, the lateral direction (horizontal direction) of the sensor grid is the X axis, and the longitudinal direction (vertical direction) of the sensor grid plate is the Z axis. A position/orientation detection device for a handpiece, characterized in that the coordinate system is the C system. In any one of claims 1 to 4,
For the magnetic field vector sensor grid, a grid plate is placed at a specific position on the tip of the handpiece, and nine or more magnetic field vector sensors are placed on the grid plate at a magnetic field sensor interval of 3 to 25 mm in a plane geometric manner. using an arranged grid,
The center of the magnetic field vector sensor grid is the origin, the direction of the handpiece axis is the Y axis, the lateral direction (horizontal direction) of the sensor grid is the X axis, and the longitudinal direction (vertical direction) of the sensor grid plate is the Z axis. A position/orientation detection device for a handpiece, characterized in that the coordinate system is the C system. In any one of claims 1 to 4,
Let the position of the magnet (M(→)) in the Oh-XYZ coordinate system be (X, Y, Z), let the orientation of the magnetization vector be Θ as the rotation angle with respect to the X axis, and Φ as the rotation angle with respect to the Z axis. , the position and orientation of the magnet body (X, Y, Z, Θ, Φ) according to the Gauss-Newton method,
(1) measuring the magnetic field vector _m H (→) _ij at the position (i, j) of each magnetic field sensor of the magnetic field sensor grid fixed to the C system;
(2) Assuming that the magnet (M(→)) is at the position (X, Y, Z) and the orientation (Θ, Φ) with respect to the C system, the position (i, j ) to calculate the theoretical value of the magnetic field vector _t H(→) _ij ,
(3) calculating the measurement error by e _ij = _t H(→) _ij − _m H(→) _ij ;
(4) Calculate the sum of squared errors by E _ij =Σe _ij ² ,
(5) Calculate x, y, z, θ, and φ that minimize the error sum of squares,
(6) find the positions X, Y, Z of the magnet and the orientations Θ, Φ;
Position accuracy of 0.5 mm or less, orientation accuracy of 1 degree or less, position and orientation are measured at a measurement sampling rate of 1 to 50 Hz, and data is calculated at a rate of 1 Hz to 50 Hz. Orientation detection device. A guidance system for performing dental treatment by gripping the handpiece according to any one of claims 1 to 5 with a robot hand of an automatic control device,
(1) In advance, the coordinate position of the distal end A of the handpiece in the handpiece C system, the coordinate position of the treatment position B in the Cm system in the oral cavity, and the direction of drilling are rotated at a β angle about the Y axis as the rotation axis. , Next, input the γ angle rotation with the X axis as the rotation axis and the depth H of the hole,
The tip of the handpiece is held horizontally and held close to the magnet installed on the tooth, this state is defined as the initial position of the guidance system, and the coordinate system C in this state is defined as the C1 system,
measuring the magnetic field emitted from the magnet by the sensor grid with the magnetic field vector sensor, calculating the position (x, y, z) and the orientation (θ, φ) of the magnet;
(2) Rotate the direction of the handpiece by -θ around the Z axis to set the coordinate system C in this state to the C2 system, calculate the angle α between the treatment position B and the Y axis,
(3) Rotating the Z axis of the handpiece at an angle of α about the rotation axis to orient the handpiece in the direction of the treatment position B; After that, in order to orient the drill in the direction of drilling, the coordinate system C in which the Y axis is rotated by β angle around the rotation axis and then rotated by γ angle around the X axis is assumed to be C3 system,
Calculate the position (x, y, z) and orientation (θ, φ) of the magnet body, calculate the positional relationship AB between the position A of the tip of the handpiece and a predetermined treatment position B,
(4) Move the tip A of the handpiece along the Y-axis, guide it to a predetermined treatment position B and stop it, and let the coordinate system C in this state be the C4 system,
The position (x, y, z) and orientation (θ, φ) of the magnet body were calculated, and the positional relationship between the position A of the tip of the handpiece and the predetermined treatment position B was calculated. Confirm that the misalignment with the following is 1 degree or less,
(5) If not, finely move each axis to correct the misalignment to 0.1 mm or less, and slightly rotate each axis about the rotation axis so that the misalignment is 1 degree or less. , and the coordinate system C in this state is defined as the C5 system,
(6) moving the handpiece in the specified direction by the specified distance H to complete the treatment, and let the coordinate system C in this state be the C6 system;
Calculate the position (x, y, z) and orientation (θ, φ) of the magnet, confirm that the position A of the tip of the handpiece is at the depth H in the direction of the specified hole,
(7) The handpiece is returned by H along the Z-axis of the C6 system, then moved along the Y-axis by the distance AB as it is by the distance vector between origins (-X, -Y, -Z), and C4 By returning to the position of point A in the system,
A handpiece guidance system characterized by automatically controlling implant drilling. In claim 8,
Instead of an automatic control device, the operator holds the handpiece by hand,
(1) The operator memorizes the specified input values, the positions of points A and B, the direction of drilling and the depth H of the hole,
Hold the tip of the handpiece horizontally and close to the magnet installed on the tooth. In this state, calculate the position (x, y, z) and orientation (θ, φ) of the magnet body, and the initial position of the guidance system. , the value is conveyed to the operator to assist, and the coordinate system C in this state is C1,
(2) When the operator rotates the Z-axis by -θ with the direction of the handpiece as the rotation axis, the change in rotation angle during rotation is assisted by the operator, and the handpiece stops when the amount of rotation reaches θ. Then, with the coordinate system C in this state as the C2 system, calculate the angle α between the treatment position B and the Y axis,
(3) The operator rotates the handpiece at an angle α with the Z axis of the handpiece as the rotation axis to orient the handpiece in the direction of the treatment site B, and then directs the drill in the direction of drilling using the Y axis as the rotation axis. When rotating the angle β and rotating the angle γ with the X axis as the rotation axis, the change in the rotation angle is communicated to the operator to assist, and when the predetermined amount of rotation is reached, the operator stops, and the coordinate system in this state. The position (x, y, z) and orientation (θ, φ) of the magnet body are calculated using C as the C3 system, and the positional relationship AB between the position A of the tip of the handpiece and the predetermined treatment site B is calculated (4). The operator moves the tip A of the handpiece along the Y-axis and is guided to a predetermined treatment position B. During movement, the position (x, y, z) and orientation (θ, φ) of the magnet are changed. The positional relationship between the position A of the tip of the handpiece and the predetermined treatment position B is calculated, the amount of movement is communicated to the operator to assist, the operator reaches point B and stops, and the coordinate system C in this state is calculated. C4 system,
Confirm that the positional deviation between the two is 0.1 mm or less and the azimuth deviation is 1 degree or less,
(5) If not, the operator finely moves each axis to correct the positional deviation to be 0.1 mm or less, and slightly rotates each axis about the rotation axis so that the azimuth deviation is 1 degree. Correction is made as follows, the correction result is communicated to the operator to assist, the coordinate system C in this state is the C5 system,
(6) When the handpiece is moved in a specified direction by a specified distance H, the amount of movement during movement is communicated to the operator, and when the specified value H is reached, the operator can finish processing. and let the coordinate system C in this state be the C6 system,
Calculate the position (x, y, z) and orientation (θ, φ) of the magnet body, and confirm that position A of the tip of the handpiece is at depth H in the direction of the drilled hole. ,
(7) The handpiece is returned by H along the Z-axis of the C6 system, then moved along the Y-axis by the distance AB as it is by the distance vector between origins (-X, -Y, -Z), and C4 A handpiece guidance assist system characterized in that, in the operation of returning the system to the position of point A, the moving distance during the operation is communicated to the operator to facilitate implant drilling.

Images