JP6692876B2 - Medical device - Google Patents

Description

  The present invention relates to a method for obtaining information about the position and / or orientation of a magnetic component with respect to a magnetic detector. The invention also relates to a system comprising an imaging probe for imaging at least a part of a patient's tissue and a magnetic detector for detecting the position and / or orientation of a magnetic component with respect to the magnetometric detector. Further, the present invention provides a medical device, at least a portion of which is insertable into a patient's tissue, including a magnetic component, and position and / or orientation information regarding at least a portion of the medical device. And how to get. And, the present invention relates to an apparatus for magnetizing an elongated medical device.

  In various medical procedures involving insertion of the medical device into the patient's tissue, such as minimally invasive procedures and local anesthesia, it is not known to be precise in the patient's tissue. , Very advantageous for doctors. For example, a needle may be guided to the region of interest with the aid of ultrasound imaging to introduce local anesthesia, including peripheral nerve blocks for surgical or post-operative analgesia. However, it has been found that the difficulty of accurately detecting the end point of the needle in the ultrasonic image is high.

  Northern Digital Inc., Ontario, Canada (www.ndigital.com) offers an electromagnetic detection system under the trade name "Aurora". is doing. The system comprises an electromagnetic field generator for generating an electromagnetic field and various sensor coils responsive to the electromagnetic field generated by the generator. One or more sensor coils may be used to measure the position of the tip of the device, or the shape of the device when multiple coils are incorporated, in real time, such as a biopsy needle, catheter or flexible endoscope. It may be incorporated in medical equipment of. The various sensor coils available differ in shape and size and detect the relative position of the sensor coil with respect to the electromagnetic field of the generator in three-dimensional space and the orientation of the sensor coil in two or three dimensions. It is possible. The sensor coil is connected by a wire to a sensor interface unit that sends the coil data to the system control unit. The system control unit collects the information obtained from the sensor coil and calculates the position and orientation of the sensor coil.

  "Evaluation of a miniature electromagnetic position tracker", Mat. Phys. (2002), 29 (1), 2205 ff) Hummel et al. Study the effect of the presence of an ultrasonic scanning head on the accuracy of "Aurora" electromagnetic tracking system measurements.

  Placidi, G. et al., "Patient critique of magnetic localization system for in vivo catheterization," latest biotechnology patent (2009), pp. 2, 58 et seq. of Patents about Magnetic Localization Systems for in vivo Catheterizations ", Rec. Pat. Biomed. Eng. (2009), 2, 58 ff), the magnetic field is outside the patient's body (as seen in the" Aurora "system). A distinction is made between “externally generated magnetic field” systems and systems in which the magnetic field is generated by permanent magnets within the patient's body (“internal permanent magnets”). A system capable of detecting the three-dimensional position and the two-dimensional orientation of a permanent magnet that is permanently fixed to an internal medical device has been studied. Each measurement involves at least two spatially separated 3-axis magnetic sensors for measuring the x, y and z components of the magnetic field produced by the permanent magnet at at least two spatial positions. Six magnetic sensors are arranged in a circle surrounding the patient to ensure that each part of the patient's body is covered by at least two sensors. Prior to use, the system is calibrated to take into account the earth's magnetic field. In the calibration step, the earth's magnetic field is measured without permanent magnets and then subtracted from each subsequent measurement. The position of the magnet is calculated from the residue. It is believed that a disadvantage of this system is that it cannot be moved once it has been calibrated.

  Also, U.S. Pat. No. 6,263,230, cited in the above-cited article by Prasidi et al., Describes a "continuous automatic recalibration" system in which the detector can be moved after initial calibration, if not at the same time as the magnet. There is. To detect the position of the permanent magnet of the indwelling medical device, a magnetic detection system is attached to the fluoroscopic head in a known spatial relationship and the magnetic field is approximated as a dipole field. To compensate for the earth's magnetic field and its associated local perturbations, an initial calibration is performed prior to the magnet being introduced into the patient. An offset value is determined for each magnetic sensor of the detector system. Then, when the magnet is introduced into the patient, the respective offset values are subtracted from the respective magnetic sensor readings to compensate for the earth's magnetic field and its local perturbations. Also, the "continuous automatic recalibration" scheme makes it possible to compensate for local perturbations of the earth's magnetic field, even if the detection system is moved. According to this method, the detector is moved while leaving the magnet at a position known from the previous measurement. The exact position change of the detector is tracked by the digitizing arm, which calculates the magnetic field due to the magnet at the new position of the detector. The result is subtracted from the magnetic field actually measured by the detector, the remainder of which is considered to be the contribution of the earth's magnetic field at the new location. This process may be repeated as the detector is moved to another position.

  U.S. Patent No. 6216029 discloses a device for ultrasonic freehand guidance of a needle. Both the ultrasonic probe and the needle or needle guide are provided with a plurality of orientation sensors for sensing the position of the probe and needle with respect to a reference. Each orientation sensor may comprise three transponders in a triangular array. The transponder is preferably an electro-optical sensor operating in infrared or visible light. Alternatively, the system comprises a magnetic transmitter and a magnetic receiver attached to each of the ultrasound probe and the needle or needle guide. An ultrasound image of the target area is displayed on the display screen. The needles are also displayed as clearly colored lines, even when the needles are outside the ultrasound image. Additionally or alternatively, the needle trajectory is displayed.

  Similarly, US Pat. No. 6,733,468 discloses a diagnostic medical ultrasound system in which both the ultrasound probe and the invasive medical device (eg, cannula) are at their respective locations and positions. And / or has a position sensor attached to each for transmitting orientation. The position of the needle and the probe determines the relative position of the needle with respect to the imaging surface of the probe. Thereby, the projected trajectory and the actual trajectory of the invasive medical device are calculated and superimposed on the ultrasonic image.

  It is an object of the invention to provide an improved method of obtaining information about the position and / or orientation of a magnetic component with respect to a magnetic detector. The invention also provides an improved imaging probe for imaging at least a portion of a patient's tissue and a magnetometric detector for detecting the position and / or orientation of a magnetic component relative to the magnetometric detector. The purpose is to provide a system. Further, the present invention provides an improved medical device, at least a portion of which is insertable into the tissue of a patient, the magnetic device comprising a magnetic component, and at least a portion of the medical device. It is an object to provide an improved method of obtaining position and / or orientation information about a. And, the present invention aims to provide a novel apparatus for magnetizing an elongated medical device.

  In the following, the invention will be described with reference to the claims. It should be noted that the reference numbers in all claims have no limiting effect and are intended to improve readability.

(Method of obtaining position and / or direction information)
According to one aspect of the invention, the problem is solved by providing a method having the features of claim 1. Therefore, according to the invention, the position and / or orientation of the magnetic component with respect to the magnetometric detector is directly obtained. Advantageously, by combining the results of at least two simultaneous measurements, the effects of secondary magnetic fields are computer-eliminated, so that offset values for compensating for the earth's magnetic field can be obtained, for example in US Pat. It is not necessary to perform the initial calibration step used in the method described in 6263230. Also, the "continuous automatic recalibration" procedure disclosed in the document relies on a digitizing arm to measure the position change of the detector and requires that the magnetic component remain stationary while the detector is moved. However, this procedure can be avoided. On the contrary, it is possible to derive the position and / or orientation of the magnetic component, even if the magnetometric detector and the magnetic component are moved simultaneously. This is especially true when the magnetometric detector is attached to a portable probe, such as an ultrasonic probe for ultrasonic assisted medical procedures that track the position of the medical device relative to the patient tissue image produced by the probe. In, it will be a big profit. In such cases, it is almost impossible for the physician to keep the probe stationary while the medical device is being moved. Also, advantageously, the digitizing arm of US Pat. No. 6,263,230 can be dispensed with, so that the means for detecting the position and / or orientation of the magnetic component according to the present invention is a physical reference. No need for contact. In fact, it is achievable to dispense with means other than magnetic components as a reference in order to provide the desired information regarding the position and / or orientation of the magnetic components. This is in contrast to the teachings of US Pat. No. 6,263,230 as well as, for example, the teachings of US Pat. No. 6216029 and US Pat. No. 6,733,468. Since the quantity of interest, ie the position and / or orientation of the magnetic component with respect to the probe, is obtained directly, an estimation method which relies on separate estimates for the probe position and the position of the magnetic component, eg US Pat. No. 6216029 and An estimation error is less likely to occur as compared with the method disclosed in US Pat. No. 6,733,468.

  Also, advantageously, by combining the results of two measurements that are made essentially simultaneously to obtain the position and / or orientation of the magnetic component, the magnetic component is subjected to an external magnetic field to compensate for the earth's magnetic field. It is possible to dispense with the procedure of relying on the oscillating magnetic field of, i.e., the procedure disclosed in the above-referenced article of Placidi G.

  In the context of the present invention, a "magnetometric detector" is a device capable of obtaining quantitative information about the magnetic field it is exposed to, for example the absolute value, direction and / or gradient of the magnetic field. The magnetometric detector may include one or more magnetometers. The expression "spatial associated" with respect to a plurality of positions at which measurements are made and a magnetic measurement detector means that the plurality of positions are detected such that the position and orientation of the detector can be derived from the arrangement and orientation of the plurality of positions. It means to move in synchronism with the vessel (and thus in multiple positions in synchronism with each other).

  The "secondary magnetic field" should generally include the earth's magnetic field. In addition, "secondary magnetic field" includes distortions of the earth's magnetic field or other magnetic fields, such as those generated by devices in the vicinity of a magnetometric detector or distortions thereof. The preferred secondary magnetic field is essentially uniform in the space in which the magnetometric detector moves when the magnetometric detector is used.

  A "magnetic component" is an entity that produces its own magnetic field. The magnetic component, due to its magnetic nature, can provide the magnetometric detector with information regarding its position and / or orientation.

  "Information about position" of a magnetic component refers to a position in at least one spatial dimension, more preferably a position in two dimensions, even more preferably a position in three dimensions. Similarly, "information about orientation" of a magnetic component refers to orientation in at least one spatial dimension, more preferably orientation in two dimensions, and even more preferably orientation in three dimensions. The information obtained is preferably the position and / or orientation of the magnetic component within a predetermined resolution. Also, even information simply as to whether the magnetic component is within the imaging plane of the imaging probe may constitute position information within the scope of the invention. Furthermore, the information that the magnetic component is in front of or behind the imaging surface also constitutes position information.

  The problem associated with the invention is also solved by providing a method having the features of claim 3. The method according to claim 3 can advantageously take advantage of the fact that from the measurement of the inertial measurement unit the orientation of the magnetic measurement detector or both the orientation and the position can be derived. From the result, the azimuth or the azimuth and intensity of the secondary magnetic field, preferably the earth magnetic field, with respect to the detector can be derived respectively. For this reason, preferably in the initial calibration step, the orientation, or strength and orientation, of the secondary magnetic field with respect to the magnetometric detector is measured without magnetic components. By tracking the orientation change of the magnetic measuring device from the initial calibration position, it is possible to calculate each component of the secondary magnetic field which is approximated to be spatially and temporally constant.

  In the context of the present invention, an "inertial measurement unit" is a unit comprising a gyroscope and / or an accelerometer, preferably both. As with the solution of claim 1, advantageously no reference means other than the magnetic component is required to provide the desired information regarding the position and / or orientation of the magnetic component.

(System with imaging probe and magnetic measurement detector)
According to another aspect of the invention, the problem associated with the invention is also solved by providing a system having the features of claim 18.

  A "portable probe" is a probe intended for use held in a desired position by the user's hand. In particular, portable probes lack technical means such as support arms, runners or wires that can hold the probe in a position where the user releases his hand. A preferred portable probe comprises a handle.

  The problem associated with the invention is also solved by providing a system having the features of claim 19. The fastener allows the magnetometric detector according to the invention to be attached to an imaging probe that was not originally designed (or at least not dedicated) for the use of the magnetometric detector according to the invention. Preferably, the fasteners are fixedly attached to the imaging probe and / or the magnetometric detector. The plurality of fasteners may be provided as separate pieces, and the fastener may include a portion (eg, a self-adhesive portion) for fixedly attaching the fastener to the imaging probe and / or medical device. ..

(Medical device and method for obtaining position and / or orientation information regarding medical device)
According to yet another aspect of the invention, there is provided a medical device having the features of claim 26 and a method having the features of claim 37 for obtaining position and / or orientation information about at least a portion of the medical device. Also solves the problem. Medical device and method for obtaining position and / or orientation information about at least a portion of the medical device is provided with a functional component (eg, cannula or metal rod) that can be magnetized to enable the medical device to be detected by a magnetometric detector. Takes advantage of the inventor's discovery that many medical devices have. Therefore, the functional components of the medical device may be assigned additional purposes beyond the original function of the functional components in the medical device, simply by magnetization.

  In the context of the present invention, a "functional component" of a medical device is a component that contributes to the functioning of the medical device in addition to providing position and / or orientation information to the magnetometric detector. That is, the functional component contributes to the medical device achieving its purpose as a medical device. In this regard, the transfer of position and / or orientation information to the magnetometric detector is not considered a function of the medical device. The function is, for example, the delivery of fluid to or from the patient's tissue when the medical device is a catheter or a cannula, or when the medical device is an electrosurgical instrument. Alternatively, it may be an electrosurgical procedure.

  Preferred magnetic components are the "essential" components of medical devices. In this context, "essentially" means that the medical device cannot serve its purpose when the magnetic component is removed. Alternatively, the magnetic component, although not essential, is beneficial. For example, magnetic components can improve the functionality, handleability or other properties of medical devices beyond providing orientation and / or position information to magnetometric detectors.

(Magnetizer)
And according to a further aspect of the present invention, the problem is solved by providing an apparatus having the features of claim 39 for magnetizing an elongated medical device. The apparatus can be used to magnetize an elongated medical device (e.g., a cannula) just before a medical procedure is performed. The device comprises both a container for holding the elongated medical device and a magnetizer, so that the cannula is a magnetic component for use in a method involving a system according to the invention or in a method according to the invention. The cannula can be easily magnetized, for example by a physician, to change to.

  Although only one magnetic component is referenced throughout the specification and claims for a better understanding of the basic idea of the invention, it is understood that the invention is, in all respects, practiced in the presence of further magnetic components. The form is also included. As will be readily apparent to those skilled in the art, the method, apparatus and system according to the invention can be applied to multiple magnetic components instead of just one magnetic component.

(Description of preferred embodiments of the present invention)
Preferred features of the invention which may be applied alone or in combination are discussed below and in the dependent claims.

(Acquisition of position and / or direction information)
Preferably, the strength and / or orientation of the magnetic field measured at one or more locations spatially associated with the magnetometric detector is the strength and / or orientation of a secondary magnetic field, ie the earth's magnetic field (possibly distorted) and / or Or it is used as a direct estimate of the bearing. For this reason, it is preferable to ensure that the measurements at this or these positions provide a direct estimate of the strength and / or orientation of the secondary magnetic field, without being sufficiently affected by the magnetic field of the magnetic component. This or these locations are sufficiently separated from the magnetic component in order to Therefore, if the magnetometric detector is integrated with or attachable to an imaging probe (eg, an ultrasonic imaging probe), it may be used in accordance with an embodiment of the invention, as discussed further below. The means of the magnetometric detector (eg a plurality of magnetometers) for measuring the strength and / or the orientation of the secondary magnetic field are such magnetometers (or one magnetometer) by means of the magnetic field of the magnetic components introduced into the tissue of the patient. A) is essentially unaffected, and is sufficiently spaced from the portion of the imaging probe that is in close proximity to the patient.

  In the context of this embodiment, "direct estimates" means that measurements at single or multiple positions estimate the strength and / or orientation of the secondary magnetic field within the required accuracy. Means to be sufficient.

  Advantageously, the magnetic field measured according to the above preferred embodiment of the invention is simply subtracted from the measurement result at one or more other locations to obtain a magnetic value for each of the measurements at the other locations. Only the magnetic field of the component can be obtained. This can then be used to derive the position and / or orientation of the magnetic component.

  Preferably, the position and / or orientation of the magnetic component is derived from a model of the magnetic field due to the magnetic component from measurements at positions affected by the magnetic field of the magnetic component, after the secondary magnetic field has been subtracted. It is calculated computationally by fitting it to the actual magnetic field of the magnetic component. Therefore, in this model fitting procedure, the position and / or orientation of the magnetic component is an unknown parameter.

  In an alternative embodiment of the invention, a model with a uniform magnetic field corresponding to a secondary magnetic field, preferably the earth's magnetic field, is a further unknown parameter in the model, which model is unknown by a suitable algorithm. The parameters, i.e. the position and / or orientation of the magnetic component and, if desired, the strength and / or orientation of the secondary magnetic field, are further adapted to the measurement results at the plurality of positions. The method is preferably such that all positions of the magnetometric detector in which the strength and / or orientation of the magnetic field are measured are such that any of those positions directly gives an estimate of the strength and / or orientation of the secondary magnetic field. It is adopted when it is considered that it may be affected by the secondary magnetic field to the extent that it cannot be provided.

  In a variant of the above method, the effect of the secondary magnetic field on the measurement result at each position is first offset by determining the differential values of the measurement values at different positions. For example, after normalization (discussed below), the average value of the magnetic field strength and / or orientation determined at various locations may be subtracted from the magnetic field strength and / or orientation at the individual locations. Thus, magnetometers effectively act as magnetic field gradiometers. These difference values can then be fitted to a model utilizing differences in the original magnetic field or other functional or other functional derivatives.

  Also, preferably, the measured value provides a change in orientation and / or position of the magnetometric detector due to movement of the magnetometric detector. For example, the change in orientation and / or position of the magnetometric detector is obtained from the orientation of the detector with respect to the earth's magnetic field calculated by computer by combining the measurement results at two or more positions of the magnetometric detector. be able to. The orientation and position of the magnetic measurement detector can also be derived from the measured values of the inertial measurement unit. If a magnetometric detector is attached to the imaging probe, this information may be used, for example, to combine multiple images acquired by the imaging probe at different positions and / or different orientations into a three-dimensional or panoramic map. can do. In particular, this facilitates three-dimensional mapping of extended volumes. Thus, the inertial measurement unit, in particular the accelerometer, on the one hand and the measurement of the magnetic field strength and / or orientation for estimating the secondary magnetic field on the other hand are interchangeable. However, the invention also includes embodiments in which both these means are provided. In particular, the accuracy can be increased by combining the results of both means, for example by averaging the results of both means.

(Magnetic measurement detector and base unit)
In a magnetometric detector, the strength and / or orientation of the magnetic field is preferably at least two positions spatially associated with the magnetometric detector, more preferably at least three positions, even more preferably at least four positions. Measured at locations, these locations are separated from each other. By combining these measurements, the position and / or orientation of the magnetic component can be derived. By further combining these, the influence of the secondary magnetic field can be eliminated by computer.

  Preferably, the magnetic field at at least two positions, more preferably the magnetic field at at least three positions, and even more preferably the magnetic field at each position is measured by a magnetometer of a magnetometric detector, each magnetometer being at a respective position. Will be placed. Preferably, at least a second position of the magnetometric detector, more preferably a second position thereof, more preferably a third position thereof, most preferably all positions, of at least two Each component of the magnetic field is measured in a linearly independent spatial direction, more preferably in three linearly independent spatial directions.

  In a preferred embodiment of the invention, the measurement results are sent to a base unit for processing, which is separate from the magnetometric detector. In this context, "separated" means that the base unit and the magnetometric detector do not move in synchronization with each other, i.e. they are not spatially related. Rather, the magnetometric detector can move independently of the base unit. In particular, the base unit can remain stationary while the magnetometric detector (preferably attached to the imaging probe as described above) is moved. The transmission between the magnetometric detector and the base unit can be realized, for example, by a flexible cable or a wireless connection. The advantage of a wireless connection is that the magnetometric detector can be attached to a conventional imaging probe without the need for a separate cable in addition to the probe cable.

  An advantage achievable with embodiments of the present invention is that most or all of the computational calculations needed to derive the position and / or orientation of magnetic components from the measurement results can be done in the base unit. This is an over-demand for a microprocessor in which the computational means necessary to eliminate the effects of secondary magnetic fields and to derive the position and / or orientation of the magnetic components are small enough to be easily attached to the imaging probe. It is useful considering the fact that you get. Thus, by moving some or all of the computer calculations to a base unit that can easily provide sufficient processing power, the magnetometric detector can be made compact and lightweight.

  In another embodiment, the base unit is integrated with an imaging system with information from the magnetometer provided via the probe cable.

  A preferred magnetometric detector comprises several magnetometers, optionally with an inertial measuring unit, and an interface circuit, which may be a multiplexer or a microprocessor. The interface circuit allows multiple signals of multiple probes to be passed over a single cable or wireless link. The interface circuit samples the magnetometers (and also the inertial measurement unit if there is one) and optionally monitors other information such as the state of charge of the magnetometer detector battery. The information is then transmitted by the transmitter of the magnetometric detector to the receiver of the base unit.

  In the preferred embodiment of the present invention, the magnetometric detector further receives information from the base unit. Therefore, preferably bidirectional communication is possible between the magnetometric detector and the base unit. The return channel from the base unit to the magnetic measurement detector can be used, for example, to remotely reconfigure the magnetometer or inertial measurement unit from the base unit. For example, the operating range of the magnetometer can be adapted to the strength of the magnetic field of the magnetic component, in particular in order to avoid overflows in the measurement process.

  For transmission, the magnetometric detector and the base unit are functionally connected to each other. The term "functionally connected" includes both direct connections and indirect connections through one or more intermediate components. Here, the intermediate component may be a hardware component and / or a software component. Preferably, the transmission between the magnetometric detector and the base unit is encoded in a manner that prevents eavesdropping, for example by asymmetric encryption. Also, preferably, measures are taken to prevent interference when multiple systems comprising a magnetometric detector and a base unit are operating in close proximity.

  Preferably, in the calibration step, the magnetometers are calibrated for gain, offset and orientation so that within a uniform magnetic field, the magnetometers all produce essentially identical measurements. This ensures that all magnetometers will measure equal values when exposed to a uniform magnetic field. For example, when a magnetometer is rotated in a uniform geomagnetic field, the magnetometer should measure the change in intensity of the magnetic field components in three linearly independent directions, depending on its orientation. However, the total strength of the magnetic field should be constant regardless of the orientation of the magnetometer. On the other hand, in a commercially available magnetometer, gain and offset are different in each of the three directions. Also, in many cases, their directions are not orthogonal to each other. When the magnetometer is rotated in a uniform and constant magnetic field, for example as described in US Pat. No. 7,275,008 for a single sensor, the measurement results give rise to a tilted three-dimensional ellipsoid. However, since the measured magnetic field is constant, the normalized measurements should be on the sphere. Preferably, the offset value β and the gain matrix M are introduced to transform the ellipsoid into a sphere.

For multiple sets of sensors, additional steps need to be taken to ensure that the measurements of different sensors are identical to each other. Results In order to correct this, a set of gain normalization matrix M _k and the normalized offset vector beta _k is determined for each position k, using this, the raw results a _k magnetometer, normalized converted to b _k .
b _k = a _k ^* M _k + β _k

Such a set of gain matrices M _k is known in the art, eg, “Field-Calibration of Arrays of Sensors” by Dolbo et al., 2010 American Control Conference, Baltimore 2010 (Dorveaux et. Al., “On-the-field”). Calibration of an Array of Sensors ", 2010 American Control Conference, Baltimore 2010).

The defined conversion, b _k is provided in equal gain the strength of the magnetic field components in the spatial direction of the three orthogonal. Also, these directions are guaranteed to be the same for all magnetometers in the magnetometric detector. As a result, all magnetometers produce essentially the same value in any uniform magnetic field.

The normalization information M _k and β _k for each magnetometer obtained in the calibration step can be stored in the magnetometric detector or in the base unit. This information is preferably stored in the magnetometric detector because it allows easy replacement of the magnetometric detector without the need to update the information in the base unit. Because it will be. Thus, in a preferred embodiment of the invention, the magnetometer of the magnetometric device is subjected to sampling and the results are normalized in the magnetometric detector. This information, along with possibly other relevant information, is sent to the base unit for further analysis.

In another embodiment of the invention, the transform may be another more general non-linear transform _bk = F ( _ak ).

  In addition to the above calibration method, another calibration method that employs a non-uniform magnetic field to obtain the relative spatial position of the magnetometer of the magnetometric detector is applied. A standard calibration method uses a uniform magnetic field (a) aligns the measurement axes of a plurality of magnetometers in orthogonal directions, (b) offsets offset values, and (c) adjusts to equal gain, while It is further advantageous for the system described above to be able to utilize the exact relative spatial positions of the magnetometers. This can be achieved by an additional calibration step in which the magnetometric detector is exposed to a known non-uniform magnetic field. Preferably, the measured values obtained at the various positions are compared with the expected magnetic field strength and / or orientation at each temporary position, and the temporary positions until the actual measured values and the expected measured values match. Correcting allows for accurate calibration of the spatial position of the sensor.

  In a modification of the latter calibration method, an unknown, not known, non-uniform magnetic field is used. Multiple magnetometers are swept in an unknown magnetic field while changing position in a fixed orientation. With one of these magnetometers providing a reference track, the positions of the other magnetometers are adaptively changed in such a way that their measurements align with those of the reference unit. This can be achieved, for example, by a feedback loop implementing a mechano-magnetic-electronic gradient-descent algorithm. The tracks used in this non-uniform field calibration may consist of only a single point in space.

(Imaging probe and processing unit)
Preferably, the magnetometric detector is integrated or removable with the imaging probe for imaging at least a portion of the patient's tissue. "Integrated" means that the magnetometric detector is permanently fixed to the imaging probe so that it is not removed from the imaging probe when the imaging probe is used as intended. Means The magnetometric detector may be located, for example, in the housing of the imaging probe. The magnetometric detector may be bonded to the imaging probe to the extent that it can be separated from the imaging probe for inspection or repair purposes without destroying the imaging probe. In that sense, the term "integrated" also includes embodiments in which the magnetometric detector can be removed from the imaging probe for repair or maintenance purposes. In the context of the present invention, "detachable" means that when a device is used for its intended purpose, one part can be detached from another part to which the part was attached by the user. Thus, for example, a magnetometric detector remains attached to an imaging probe so that it is spatially associated with the imaging probe during a medical procedure, while after the medical procedure is over, the detector is It can be removed from the probe and attached to another imaging probe for another medical procedure. Preferably, at least one, and preferably both, of the magnetometric detector and the imaging probe are provided with one or more fasteners for purposes of removal and attachment. Preferably, the magnetometric detector and the imaging probe are attached to each other to ensure that they are in a fixed position relative to each other during use in a medical procedure.

  A preferred imaging probe is an ultrasonic imaging probe. Such an ultrasound imaging probe preferably comprises an array of ultrasound transducers. The transducer transmits ultrasonic energy, preferably in the form of ultrasonic pulses, into the area of tissue of the patient to be diagnosed. The reflected ultrasound energy returning from the area is then received and recorded by the same or other transducers. The present invention may also be used with other types of imaging probes, such as impedance imaging probes including probes of the type disclosed in Nervonix Inc. US Pat. No. 7,865,236.

  Other suitable imaging probes include IR sensors or cameras capable of measuring blood flow and / or scanning devices.

  A processing unit is also preferably provided. The position-related information generated by the magnetometric detector and the image information generated by the imaging probe are preferably transmitted from the magnetometric detector and the imaging probe to the processing unit, respectively (the position-related information is preferably Via the base unit as described above). These pieces of information are then combined in a processing unit to produce an image of the patient's tissue in which the position of at least part of the medical device is the position and / or the position obtained from the magnetometric detector. It is displayed based on the azimuth information. The preferred processing unit comprises a display device for displaying the image. In this context, "position-related information" may be, for example, raw data obtained by a magnetometer, calibration data or the actual position and orientation calculated as described above. Similarly, "image data" may be raw data obtained by the imaging probe or further processed raw data.

  In a preferred embodiment of the invention, the processing unit drives the imaging probe and interprets the raw data received from the imaging probe (eg an ultrasound probe). Also, preferably a cable or a bundle of cables is provided for connecting the imaging probe to the processing unit. If the imaging probe is an ultrasound probe, the processing unit preferably comprises drive circuitry that sends precisely timed electrical signals to the transducers of the imaging probe to generate ultrasound pulses. When part of the ultrasonic pulse is reflected back from the area to be diagnosed back to the ultrasonic probe, the received ultrasonic energy is converted into an electrical signal, which is then transferred to the processing unit. .. The processing unit amplifies and processes this electrical signal to produce an image of the diagnostic region of the tissue of the patient.

  Since the position information of the medical device is obtained by detecting the position of the magnetic component of the device, the part of the medical device in which the position is displayed is preferably the magnetic component or another component of the medical device. It must be either and its relative position to the magnetic component is known. In one embodiment of the invention, only a portion of the magnetic component is shown, eg, the most distal portion, such as the distal end of the cannula.

  The former component is functionally connected to the processing unit for the transmission of information from the magnetometric detector and the imaging probe to the processing unit (preferably via the base unit). Preferably, the processing unit is further functionally connected (preferably via the base unit) to further receive information from the base unit. In this way, relevant information may be sent from the processing unit or the magnetometric detector to facilitate the computer calculations performed therein.

  It would be most convenient if the image generation processing units were bidirectionally connected. Preferably, the information obtained by processing the recorded images in the processing unit can be transmitted to the base unit to facilitate the estimation of the needle position and vice versa. For example, a Hough transformation (Hough-Transformation) for a raw ultrasonic image can detect a blurred image of the needle (faint image), and this localization information from the ultrasonic image (localization information) is a constraint. It can be applied to the optimization step of deriving the same needle position from the magnetometer data. Needless to say, needle detection algorithms operating directly on the image can also be stabilized through information about the needle position coming from the base unit.

  Preferably, in the image, it is displayed whether the medical device or a part of the medical device is arranged inside or outside the predetermined space surface. Preferably, an image of the patient's tissue in a particular plane is displayed on the display, which particular plane corresponds to the predetermined spatial plane. The surface to be displayed may be determined by the position and / or orientation of the imaging probe, for example. For example, if the imaging probe is an ultrasound imaging probe operating in 2D mode, the surface to be displayed is the imaging surface of the probe. Preferably, when multiple parts of the medical device are displayed, which part is located in the spatial plane, which part is located on one side of the spatial plane, and which It shows if the part is located on the other side of the space plane. For example, the imaging surface of the imaging probe may be associated with one color, one side of the imaging probe (imaging surface) may be associated with another color, and the other side with a third color. May be associated with. Alternatively or additionally, the trajectory of a magnetic component or a portion of a medical device may be displayed, for example, as disclosed in US Pat. No. 6,733,458. If the imaging device is primarily a 3D device, the above description naturally extends to the 3D volume. Therefore, particularly in such a case, it may be displayed in the image whether the medical device or a part of the medical device is inside or outside the predetermined volume, and on the display, An image of the tissue of the patient within the particular volume may be displayed, the particular volume corresponding to the predetermined volume. The displayed volume may be determined by the position and / or orientation of the imaging probe, for example.

(Magnetic components and medical devices)
The magnetic component is preferably integrated with the rest of the medical device. Alternatively, the magnetic component may be a replaceable part, eg a syringe cannula.

  The functionality of the medical device preferably does not depend on the magnetic component being magnetic. That is, the medical device serves its purpose even if the component is not magnetic. For example, the cannula need not be magnetic to serve its purpose of introducing liquid into the tissue of the patient. This embodiment of the invention has the possibility that certain components of the medical device, which are not generally magnetic, will be magnetized and thus provide position and / or orientation information to the magnetometric detector. Take advantage of the fact that it can function as a magnetic component of.

  Alternatively, the magnetic component is a functional component and the function relies on the component being magnetic. In this case, the invention takes advantage of the fact that the magnetic component, in addition to performing its magnetically related function in the medical device, can also be used to provide position and / or orientation information.

  The inventor has found that magnetic components, especially magnetic components of medical devices, can be reliably detected by commercially available conventional magnetometers. The magnetic field of the magnetic component is preferably not an alternating magnetic field, ie it does not change its sign or orientation periodically. The magnetic field of a preferred magnetic component does not change in the sense that it retains its orientation and / or absolute value for a medical device that is tracked to be essentially constant during a consultation, procedure or surgery. It has been found that such magnetized medical devices are reliably detected by magnetometric detectors with the magnetization kept sufficiently constant during a typical medical procedure.

  The preferred magnetic component is at least partially a permanent magnet. In the context of the present invention, a "permanent magnet" is an object that is magnetized, thereby producing its own persistent magnetic field due to remanence. Advantageously, since it is a permanent magnet, no power supply is needed.

  While permanent magnets are preferred, embodiments in which the magnetic component is a non-permanent magnet (eg, an electromagnet, eg, a solenoid to which electric current may be applied to generate a magnetic field) are also encompassed by the present invention. Also, in some embodiments of the present invention, a portion of the magnetic component may be magnetic simply due to magnetic induction from another portion of the magnetic component (eg, the permanent magnet portion of the component). On the other hand, in other embodiments of the invention, such induction is not involved. The part of the magnetic component that induces the magnetic field in the other part does not necessarily have to be integrated with the other part. Rather, the two parts may be separated. Further, the two parts do not necessarily have to be close to each other, and may be separated from each other by a certain distance. In practice, in general, a magnetic component may consist of one component, but some discrete parts spaced apart from each other, such as several arranged in a row within a medical device. It may consist of a permanent magnet. However, a component of a medical device (eg, a coil of a radio frequency antenna) that becomes magnetic only due to guidance from the outside of the medical device does not generate its own magnetic field and thus is magnetic in the context of the present invention. It should not be considered a component.

  The magnetic component or part of the magnetic component may be a magnetic coating. Preferably, the coating is a permanent magnetic coating. Thus, the coating may be, for example, permanently magnetic particles, more preferably nanoparticles. "Nanoparticles" are particles with a size of 100 nm or less in at least two spatial dimensions.

  In one embodiment of the invention, the magnetic component has an essentially uniform magnetization. In another embodiment, the magnetization is non-uniform in at least one dimension, ie, the magnitude and / or direction of the magnetic moment is varied as a function of position on the magnetic component to cause the magnetic pattern in one or more dimensions. , Which is similar to that of a conventional magnetic memory strip (at least one dimension) or disk (two dimensions), such as is used, for example, in credit cards for the storage of information. In a preferred embodiment of the invention, the one-dimensional magnetic pattern may be recorded along the longitudinal direction of the elongated magnetic component (eg cannula). Advantageously, such a pattern may be convenient for identifying a magnetic component, and thus a device to which the magnetic component is attached or a device of which the magnetic component is a part (eg, a medical device). ) May be useful for document management purposes. Also, by marking specific parts of a medical object with different magnetic codes, these parts can be distinguished. A achievable advantage of this embodiment of the invention is that the individual parts of the magnetic component are identifiable and can be individually tracked with respect to their position and / or orientation, so that Or, it is a point where the orientation can be better determined. In particular, it is possible to advantageously track a changing shape of the magnetic component, eg a needle that is bending under pressure. In addition, the deformed magnetic component and / or the deformation or the degree of deformation of the component can be more easily determined.

  A preferred medical device is elongated, i.e. its length is at least twice its width. More preferably, at least a portion of the medical device insertable into the tissue of a patient is elongated.

  Preferably, at least a portion of the medical device insertable into the tissue of the patient, and more preferably the entire medical device, is tubular. Also preferably, the magnetic component is partially tubular. Alternatively, the portion of the medical device or medical component insertable into the tissue of the patient may have a non-tubular shape, for example when the medical device is an electrosurgical instrument, eg It may have a rod-like shape. In a preferred embodiment of the invention, at least a portion of the insertable medical device, and more preferably the entire medical device, is a cannula. And the cannula also constitutes the magnetic component. The preferred cannula has a beveled end that is used to introduce the cannula into the tissue of the patient.

  Many cannulas are easily bent, so the position of the inserted portion of the cannula, especially the cannula end, can be easily determined from the position of the needle guide as disclosed in US Pat. No. 6216029. Since this is not the case, the present invention is particularly suitable for use with such cannulas. As will be shown in the detailed description below, the model magnetic fields used in the preferred embodiment of the present invention assume only two spaced apart magnetic quantities, one of which is the needle end. The deviation of the actual magnetic field from the model magnetic field is relatively small for the slight needle curvature that normally occurs, so even if the needle is curved, the above model can be easily applied to determine the position of the needle end. It was found to be inferrable.

  The present invention may be used to particular advantage with a cannula for local anesthesia. On the other hand, the present invention may also be used with biopsy cannulas and catheters, such as catheters for local anesthesia. The preferred solid material of the cannula or catheter is permanently magnetized, or the cannula or catheter is provided with a magnetic coating as described above. Alternatively or additionally, the cannula or catheter may be provided with a solenoid coil, preferably at its distal end.

(Magnetizer)
A preferred apparatus for magnetizing the elongated medical device comprises a magnetizing aperture. A magnet is preferably positioned near the magnetized aperture to magnetize the elongated medical device as it passes through the opening. Preferably, the opening in the apparatus is an opening in the container and the elongated medical device is capable of being withdrawn from the container through the opening so that when the elongated medical device is removed from the container. The elongated medical device is magnetized. Preferably, while the plurality of elongated medical devices are contained within the container, they are kept in a sterile packaging separate from the container. Preferably, they remain in this package while they are magnetized.

  A preferred elongated medical device is a cannula, rod or needle. A preferred container can hold two or more medical devices at the same time.

  The magnet is preferably an electromagnet, for example a solenoid, more preferably a ring-shaped solenoid electromagnet. Alternatively, it may be a permanent magnet. The magnetizing device can be designed to uniformly magnetize the inserted medical device or to record a magnetizing pattern along the elongated medical object. This may be useful, for example, to identify medical objects used for document management purposes such as those mentioned above. Preferably, changing the magnetization along the longitudinal direction of the elongated medical device can be accomplished by changing the magnetic field of the solenoid as the elongated medical device advances through the magnetized aperture. To control changes in the magnetic field, the advancement of the elongated medical device can be recorded, for example, by a measurement roll that contacts the elongated medical device as it passes through the magnetizing aperture. In another embodiment, the magnetizing device is a hollow tube composed of separate segments of magnets. By applying different electrical currents to different parts of the tube, a magnetic pattern can be imprinted on the medical device.

  By providing multiple markings on the device for alignment of the magnetometric detector and the elongated medical device, the device can be developed into a calibration tool. Preferably, for alignment, the magnetometric detector is integrated or attached to the imaging probe and the imaging probe is aligned with the elongated medical device using the markings. Thus, the magnetometric detector is aligned with the medical device via the imaging probe.

  The markings allow the elongated medical device and magnetometric detector to be placed in well-defined relative positions. This allows certain parameters of the elongate medical device, most preferably its length and magnetic moment, to be measured based on the measurements of the magnetic measuring device for computer calculation after cannula position and orientation during the medical procedure. Can be easy. In fact, these parameters can greatly enhance the fitting of the model to the parameters measured by the magnetometer as described above.

  The present invention will be described in more detail with reference to the schematic drawings.

1 is a diagram schematically showing an imaging system including an imaging probe, a magnetic measurement detector and a medical device according to the present invention. FIG. 3 is a block diagram of a magnetometric detector according to the present invention. FIG. 3 is a block diagram of a base unit according to the present invention. FIG. 5 is a diagram schematically showing three examples of images of a patient's tissue in which the position and orientation of the cannula according to the first embodiment of the present invention are superimposed. It is a figure which shows typically the magnetic measurement detector by 2nd Embodiment of this invention. FIG. 6 shows a system with an ultrasonic imaging probe and the magnetometric detector shown in FIG. 5. FIG. 7 illustrates absolute gradient magnetic field strength in the embodiment of FIGS. 5 and 6 as a function of needle distance from the imaging surface of the ultrasound imaging probe. FIG. 6 shows a magnetizing device for magnetizing a cannula according to the invention.

  The imaging system 1 shown in FIG. 1 includes a portable ultrasonic probe 2 connected to a processing unit 4 via a cable 3 as an imaging probe. The processing unit 4 drives the ultrasonic probe 2. That is, the processing unit 4 transmits an electric signal to the ultrasonic probe 2 to generate an ultrasonic pulse, interprets raw data received from the ultrasonic probe 2, and scans the raw data with the ultrasonic probe 2. Assemble into an image of the patient's tissue. A battery-type magnetic measurement detector 5 is attached to the ultrasonic probe 2 with a Velcro (registered trademark) fastener (not shown). Positioning elements are provided on the magnetometric detector 5 in order to ensure that it is always mounted in the same well-defined position and orientation when it is reattached to the ultrasonic probe 2. It is provided.

  The magnetometric detector 5 comprises magnetometers 14, 15 (not shown in FIG. 1) and is connected wirelessly or by other means to the base unit 6 bidirectionally (indicated by the flash symbol 7). ing. To that end, both the magnetometric detector 5 and the base unit 6 are provided with wireless transceivers. The transceivers may employ, for example, a Bluetooth (registered trademark) standard or a standard in the WIFI (registered trademark) (IEEE 802.11) standard family. The base unit 6 receives the normalized result of the measurements of the magnetometric detector 5 and from this result calculates the position of the magnetic medical cannula 8 and, in some embodiments, the position of the cannula 8. And calculate the bearing. Along with the measurement result, additional information such as the state of charge of the battery of the magnetic measurement detector 5 is transmitted from the magnetic measurement detector 5 to the base unit 6. Also, the configuration information is transmitted from the base unit 6 to the magnetic measurement detector 5.

  The base unit 6 transfers the calculation result, ie the position information or in some embodiments position and orientation information, to the processing unit 4. For this reason, the base unit 6 includes, for example, a USB (registered trademark) (universal serial bus) connector, a FireWire (registered trademark) (also referred to as iLink (registered trademark) or IEEE 1394) connector, or a Thunderbolt (Thunderbolt) connector. ) (Registered trademark) (also referred to as Light Peak (registered trademark)) connector or the like, and may be connected to the processing unit 4 via a standardized serial connector. In the processing unit 4, the information received from the base unit 6 and the ultrasound image are combined to generate an image of the patient's tissue on the display screen 9 of the processing unit 4, the tissue of the cannula 8 being included in the image. The current position within is displayed. The base unit 6 also receives setting information and / or prior information regarding the position of the cannula 8 from the processing unit 4 via the same connection.

  The components of the magnetometric detector 5 are shown schematically in more detail in the block diagram of FIG. The magnetometric detector 5 comprises an array 10 of two or more (eg four) magnetometers 14, 15 (not shown in FIG. 2) which are subjected to sampling by a microprocessor 11. The microprocessor 11 normalizes the measurement result obtained from the magnetometer array 10 and transfers it to the transceiver 12, and the transceiver 12 has an antenna 13 that sequentially transmits the information to the base unit 6. .. In a modified version of this embodiment, the magnetometric detector 5 is provided with a multiplexer rather than the microprocessor 11 and the normalization is performed by the processor 18 in the base unit 6.

Each magnetometer 14, 15 in the array 10 of magnetometers 14, 15 has a magnetic field component a _k ^u , a _k ^v , a _k ^w (at the position of the magnetometer 14, 15 in three linearly independent directions. k represents each magnetometer). The microprocessor 11 is responsible for these raw values.
a _k = (a _k ^u , a _k ^v , a _k ^w )
And by adding the normalized offset vector beta _k with multiplying normalized matrix M _k into three values a _k obtained from the magnetometer, i.e.,
b _k = a _k ^* M _k + β _k
By the corresponding normalized value b _k = (b _k ^x , b _k ^y , b _k ^z ) in a given orthogonal direction of equal gain
Convert to.

This same transformation is performed for all magnetometers, and all magnetometers have their normalization matrices such that the result b _k for each magnetometer yields a component of the magnetic field in the same orthogonal spatial direction of equal gain. And addition of the normalized offset vector. Thus, for a given uniform magnetic field, all magnetometers will always yield the same value after normalization, regardless of the strength or orientation of that uniform magnetic field. Each normalization matrix and normalization offset vector is permanently stored in memory associated with the microcontroller.

The base unit 6, which is shown schematically in more detail in FIG. 3, receives, via its receiver 16 and antenna 17, the normalized position information from the magnetometric detector 5 and sends that information to the processor 18. Forward. There, the normalized results of the multiple measurements are combined to derive the position (or position and orientation) of the cannula 8. Therefore, each value b _k is applied to the model of the combination of the magnetic field derived from the magnetic cannula 8 and the earth magnetic field. The unknown parameters p in this model are the position 1 of the cannula relative to the ultrasound probe, the length and orientation d of the cannula, and the magnetic coercive force m of the cannula and the earth's magnetic field E.
p = {l, d, m, E}

The unknown parameters are obtained by modeling the magnetic and magnetic fields of the magnetic cannula, in which case
c _k (p) = {c _k ^x (p), c _k ^y (p), c _k ^z (p)}
Is the normalized component of the model magnetic field at the position of magnetometer k for a given set of parameters p. The actual measured component of the component of the magnetic field according to this model Σ _k (b _k −c _k (p)) ² by suitable algorithms known to those skilled in the art.
The parameter p with the smallest deviation from is obtained. Suitable minimization techniques are, for example, gradient-descent algorithms and Levenberg-Marquardt approaches. Also, such optimization can be performed continuously using Kalman filter techniques or similar iterative means.

If the cannula is sufficiently stiff, i.e., it has little curvature, it can be approximated as a straight hollow cylinder. The magnetic field of such a cylinder is equivalent to the magnetic field of the opposite poles (ie exhibiting opposing magnetic forces) evenly distributed on the two end faces of the cylinder, ie on the two rings with the opposite poles of the opposite ends of the cannula. Is. Considering the small diameter of the cannula, the magnetic charge can be further approximated by a two-point magnetic charge at both ends of the cannula. Therefore, according to this model, the magnetic field of the cannula extending along the vector d is measured from position r _k as
N (r _k , d, m) = m ^* (r _k / | r _k | ³ − (r _k + d) / | r _k + d | ³ )

Here, | r _k | and | r _k + d | are absolute values of the vectors r _k and r _k + d, respectively. The position r _k is the relative position of the cannula 8 to the ultrasonic probe 2 using the known positions of the magnetometers 14 and 15 in the magnetic measuring detector 5 and the relative position of the magnetic measuring detector 5 to the ultrasonic probe 2. Can be converted to a specific position l. As a result, when the earth magnetic field E is further considered, each magnetic field component by this model is
c _k (p) = N (r _k , d, m) + E = m ^* (r _k / | r _k | ³ − (r _k + d) / | r _k + d | ³ ) + E
Becomes

  Note that, in contrast to many known approaches, the model does not assume that the needle magnetic field is a dipole field. This is because the magnetometric detector is typically too close to the needle compared to the length of the needle to make the dipole field a viable approximation, which can be overly simplistic.

  The values obtained by adapting this model to the actual values detected by the magnetometers 14, 15 as described above are then passed to the processing unit via the data interface 19, eg a USB® connector. 4 is transferred. There, those values are superimposed on the image of the tissue obtained from the portable ultrasonic probe 2. A method of visualizing the cannula 8 on the display screen will be described with reference to FIG. FIG. 4b shows a cross section of a blood vessel 20 imaged by the portable ultrasound probe 2 in 2D mode. Therefore, the blood vessel 20 crosses the imaging surface of the ultrasonic probe 2. It also shows schematically how the cannula 8 is visualized depending on its position relative to the imaging surface. The cannula is always visualized as a line, the end of which corresponds to the tip of the cannula. When the cannula 8 is in the imaging plane of the probe 2, the cannula 8 is represented by the first color (indicated by the solid line 21 in the drawing). On the other hand, if the cannula 8 is outside the imaging surface, it is represented by a different color, which is either in front of the imaging surface of the cannula 8 (the color shown by the broken line 22 in the drawing) or behind it (( (Indicated by a dotted line 23 in the drawing). FIG. 4a shows the cannula 8 crossing the imaging surface. In this case, the part of the cannula 8 behind the imaging surface is represented by a color different from the color of the part of the cannula 8 crossing the imaging surface, and the part of the cannula 8 in front of the imaging surface has a different color. It is represented by. The situation shown in Figure 4c differs from Figure 4a only in that the cannula 8 crosses the imaging plane at different angles. The portion of the cannula 8 outside the imaging plane is shown on the display as a vertical projection onto the imaging plane.

  In another embodiment, the full expected needle trajectory is shown on the image display, as described above. The actual position of the needle is indicated by either a different color or different line type (bold / hatch, etc.) for the needle trajectory. Also, the position across the imaging plane may be indicated by a special graphic, for example either the circle or the rectangle shown in Figure 4a. The shape or appearance of the graphic may change to indicate the likelihood that the needle will penetrate the imaging plane at that point, i.e. a general ellipse may be used instead of a circle to represent the target area. ..

  An alternative embodiment of the magnetometric detector is shown in FIGS. 5 and 6. This magnetometric detector in the first variant of embodiment comprises only one set 5 of two magnetometers 14, 15. In alternative variants of the embodiment, one or more further sets are provided at further locations on the ultrasound probe 2. It is possible to derive whether the cannula 8 is arranged within the imaging surface 24, in front of the imaging surface 25 or behind the imaging surface 24. For this reason, the magnetometers are arranged along a line parallel to the longitudinal axis of the probe. The normalized measurements of the first magnetometer 14 are subtracted from the normalized measurements of the second magnetometer 15 to effectively cancel the earth magnetic field. The difference is essentially in the direction of the needle tip as other magnetic field components due to the end of the needle decay rapidly with distance from the sensor array. Therefore, the sensor essentially "sees" only the needle tip. The relative distance can be estimated by the magnitude of the measured differential magnetic field.

  In another embodiment of the invention, magnetometers 14, 15 are aligned perpendicular to the longitudinal axis of the probe. Thus, the difference obtained is essentially the gradient of the magnetic field produced by the magnetic cannula 8. By analyzing the magnitude of the gradient, the relative distance of the cannula from the sensor can be determined. By analyzing the direction of the gradient, it can be determined whether the cannula 8 is in front 25 or behind the imaging surface 24, or directly above the imaging surface 24.

  FIG. 7 shows the absolute gradient magnetic field strength G (arbitrary unit) of the cannula 8 that is parallel to the imaging surface 24 but extends from the surface 24 at a distance Y (arbitrary unit). As can be seen, the gradient magnetic field strength G has a minimum value when the distance Y is equal to zero, ie when the cannula 8 is in the imaging plane 24. On the other hand, when the gradient magnetic field strength G is larger than the predetermined threshold value, it can be assumed that the cannula 8 is outside the imaging surface 24. In this case, the direction of the gradient magnetic field indicates whether the cannula 8 is in front 25 or behind the imaging surface 24 (not shown in FIG. 7 since FIG. 7 shows only the absolute value of the magnetic field). ). Thus, using this simple setup, the exact placement and position of the needle cannot, of course, be displayed on the ultrasound image displayed on the screen of the processing device, although for example the "* (area It is possible to superimpose “upper”, “=> (front of the imaging surface)” or “<= (rear of the imaging surface)”.

  Finally, FIG. 8 shows a device 27 for magnetizing the cannula 8 according to the invention. Inside the box-shaped device is a container (not shown) capable of holding a plurality of cannulas 8, each cannula 8 housed in a separate sterile film wrap 28. The device 27 further comprises a circular opening 29 through which the individual cannula 8 can be removed from the container together with the film wrap 28. Inside, the opening is surrounded by a ring-shaped solenoid electromagnet (not shown). The electromagnet is powered by a power supply (not shown) attached to the device. A switch on the power supply allows a current to flow through the electromagnet, which creates an electromagnetic field. The cannula 8 is then magnetized when it is removed from the box through the opening. Proper modulation of the electromagnet's current allows for coded magnetization as the needle is withdrawn from the container.

  Alternatively, there may be an opening on one side of a hollow cylinder composed of a plurality of separate magnetizing coils that allows the magnetic code to be imprinted onto the medical device in one step.

  Then, to measure the magnetic moment and length of the cannula 8, the cannula 8 is placed on the linear marking 30 of the device 27 while still contained within the transparent sterile film packaging 28. The ultrasonic probe 2 fitted with the magnetometric detector 5 is placed on another box-shaped marking 31 on the device 27. As a result, the relative position and orientation of the magnetic measurement detector 5 and the cannula 8 are known, so that the magnetic moment and length of the cannula can be easily derived from the measured values of the magnetometers 14 and 15 after normalization. it can. These values can then be used during a medical procedure to facilitate deriving the position and orientation of the cannula 8 from the magnetometer measurements according to the model described above.

  The various features described in the above description, the claims and the drawings can be related to the present invention in any combination.

Claims (5)

A medical device, at least a portion of which is insertable into a patient's tissue,
A portion of the medical device insertable into the tissue, comprising an elongated magnetic component,
The magnetic component is a cannula,
The cannula is formed of a material that is at least partially magnetizable,
The magnetization is non-uniform in at least one dimension and the magnitude and / or direction of the magnetic moment of the cannula changes as a function of position on the cannula to produce a magnetization in which more than one dimension of the magnetic pattern is produced. , Recorded along the length of the cannula ,
A medical device in which the cannula itself and individual parts of the cannula are identifiable by the one or more dimensional magnetic pattern .   The medical device of claim 1, wherein the functionality of the medical device does not depend on the magnetic component being magnetic.   The medical device according to claim 1 or 2, wherein the cannula is at least partially a permanent magnet.   The medical device according to claim 1, wherein the cannula or a part of the cannula is a magnetic coating.   The medical device according to claim 1, wherein the cannula is made of steel or spring steel.

Images