JP2001218773A - Navigation method and navigation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the three-dimensional position of a probe by an image from a certain view point. SOLUTION: A disk-like index 3 provided integrally with an operation object 2 is projected from a certain reference point 4 inside a space and the elliptic or completely round planar image of different compressions corresponding to a read angle is formed, a distance from the reference point 4 to the disk-like index is obtained based on the long axis length of an ellipse and the inclination angle of the disk-like index is obtained based on the long axis length and short axis length of the ellipse. Thus, the present position of the operation object 2 on three-dimensional coordinates set inside the space is recognized and the guidance of the operation object 2 to a desired position is supported.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a navigation method and a navigation device. More specifically, the present invention particularly relates to an improvement in means for optically measuring a three-dimensional position of a probe operated by an operator such as an operation using a CCD camera.

[0002]

2. Description of the Related Art During an operation such as neurosurgery, a navigation device is used to assist an operator in understanding the positional relationship between a surgical operation site of a patient and a tomographic image such as CT. As a result, for example, the position and posture of the probe can be recognized without directly viewing the probe.

[0003] The main three-dimensional position measurement of an operation part using this navigation device is a mechanical method,
There is a stereo vision system. In the mechanical system, the tip position coordinates are obtained by an articulated arm navigation device having a rotary encoder. In the stereo vision system, a bright spot image placed on a probe is recognized by a plurality of CCD cameras, and a three-dimensional position of the probe is calculated based on the principle of triangulation.

[0004]

However, in the mechanical method, the probe is mechanically connected to the operating table or a holding device installed near the operating table, so that mechanical interference with other surgical instruments causes a surgical operation. Not only does it become an obstacle, but depending on the joint angle, it is not possible to access the affected part smoothly,
Or, there is a difficulty in operability such as difficulty in mechanically holding the probe when the hand is released.

[0005] On the other hand, in the stereo vision system, at least two cameras need to be installed at a position apart from the surgical site, and the operator and other equipment and other devices are placed between the camera and the surgical site. There was a problem that the equipment entered and the video was interrupted. Furthermore, it has been virtually impossible to perform three-dimensional position measurement in a situation such as laparoscopic surgery where it is difficult to insert a plurality of cameras.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a navigation method and a navigation device that enable a probe to measure a three-dimensional position from an image from a certain viewpoint.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, a current position of an operation target is recognized based on three-dimensional coordinates set in a space, and the operation target is positioned at a desired position. In the navigation method that assists in guiding to, the disk-shaped index provided integrally with the operation target is projected from a certain reference point in the space, and a flat image of an ellipse or a perfect circle having a different flatness depending on the reading angle, Find the distance from the reference point to the disc-shaped index based on the major axis length of the ellipse,
In addition, the inclination angle of the disc-shaped index is obtained based on the major axis length and the minor axis length of the ellipse.

As described above, by attaching a disc-shaped index having a known radius to an operation target such as a probe, even when an image of the operation target is observed by a monocular camera, the disc is moved from the observation point (reference point) to the disk. The distance to the shape index can be calculated, and the two-dimensional position of the observed image in the field of view and the information obtained from the flatness of the image observed as an ellipse are taken into account to determine the three-dimensional position of the probe. And posture are estimated. The disc-shaped index is an ellipse on the observation image, but the major axis length of the ellipse is always equal to the diameter of the ring regardless of the inclination of the index. The distance is obtained, and the inclination of the operation target is obtained.

According to a second aspect of the present invention, in the navigation method according to the first aspect, a disc-shaped index is projected by a movement reference point at which the coordinates of the reference point can be grasped. Therefore, it is possible to capture the disc-shaped index while following the movement of the moving operation target.

[0010] The third aspect of the present invention is the first or second aspect.
In the navigation method described above, the center position is obtained by a center position index unit indicating the center of the disc-shaped index, and the long axis length and the short axis length of the ellipse are obtained based on the center position. The center position indicator makes it easy to find the center position, and allows the intersection of the long axis and the short axis to be reliably recognized.

According to a fourth aspect of the present invention, in the navigation method according to any one of the first to third aspects, an amount of rotation of the operation target object around the reading axis is obtained by an asymmetrical rotation angle indicator provided at a position other than the center. Things. Since the rotation angle indicator is provided asymmetrically, it is easy to determine how much the image of the disk-shaped indicator has rotated around the reading axis. In addition, by determining whether the surface of the disc-shaped index is closer or farther from the center of the disc-shaped index, it is easy to recognize which direction the surface of the disc-shaped index is inclined.

According to a fifth aspect of the present invention, there is provided a navigation apparatus for recognizing a current position of an operation target based on three-dimensional coordinates set in a space and assisting in guiding the operation target to a desired position. A disc-shaped index, which is an index provided integrally with the object, and which is image-recognized as an ellipse having a different flatness depending on the reading direction, and a planar image of an ellipse or a perfect circle reflecting the disc-shaped index from a certain reference point in space Image reading means for determining the distance from the reference point to the disc-shaped index based on the major axis length of the ellipse, and calculating the inclination angle of the disc-shaped index based on the major axis length and the minor axis length of the ellipse It is provided with.

According to this navigation device, since a disc-shaped index having a known radius is attached to the operation target, even when the image of the operation target is observed with a single-lens camera, the disc-shaped index is obtained from the observation point (reference point). The distance to the index can be calculated. Also, by taking into account the information obtained from the two-dimensional position of the observed image in the field of view and the flatness of the ring image observed as an ellipse, the three-dimensional position and orientation of the operation target are estimated. Is done. The disc-shaped index is an ellipse on the observation image, but the major axis length of the ellipse is always equal to the diameter of the ring regardless of the inclination of the index. The distance is obtained, and the inclination of the operation target is obtained.

According to a sixth aspect of the present invention, the image reading means in the navigation device according to the fifth aspect is a CCD camera which can move while grasping the coordinates of the reference point. Therefore, it is possible to project the disc-shaped index while following the movement of the moving operation target.

The invention according to claim 7 is the invention according to claim 5 or 6.
In the navigation device described above, a circular index portion formed of a light-emitting body or a color pattern is provided on the disc-shaped index. According to this, an elliptic image that is easily recognizable is created, and the calculation accuracy of the viewpoint distance and the posture is improved, which is preferable.

According to an eighth aspect of the present invention, there is provided the navigation device according to any one of the fifth to seventh aspects, further comprising a center position index portion indicating a center position of the disc-shaped index. Thus, the major axis length and the minor axis length of the ellipse can be obtained based on the center position, and the intersection of the major axis and the minor axis can be reliably and easily recognized.

According to a ninth aspect of the present invention, in the navigation device according to any one of the fifth to eighth aspects, an asymmetrical rotation angle index portion indicating the amount of rotation of the operation target object around the reading axis is provided at the center of the disc-shaped index. It is provided for other than the position.
Therefore, it is possible to detect the circumferential position of the recognition means and easily obtain the rotation amount of the operation target.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail based on an example of an embodiment shown in the drawings.

1 to 8 show an embodiment of the present invention. The navigation device 1 according to the present invention is a device that recognizes a current position of an operation target 2 based on three-dimensional coordinates set in a space and assists in guiding the operation target 2 to a desired position. The navigation device 1 according to the present embodiment includes a disc-shaped index 3, a surgical position searching probe 2 equipped with the disc-shaped index 3, and one CCD camera 5 for observing an image of the disc-shaped index 3. , This CCD camera 5
And an image display unit 7 for estimating the position and orientation of the disc-shaped index 3 from the image of the patient 2 and for superimposing and displaying the position of the probe 2 on a tomographic image of a patient.

The disk-shaped index 3 used in the present embodiment includes a ring-shaped index section 3a as a main index formed of a ring-shaped color pattern or a light emitting section, and a center position index section 3b as an auxiliary index for providing information on the center and rotation angle of the disk. And a rotation angle indicator 3c.

Hereinafter, the principle of measurement by the navigation device 1 of the present invention will be described.

(1) Properties of a ring in space Not only a circle but an object
(Object) has 6 degrees of freedom in the space, which is defined as follows. From a specific reference posture with the object reference point O as the origin; rotation around the z axis: rotation around the x axis: rotation around the y axis

After the rotation, the position moved spatially with respect to the point O without changing the posture is the amount of movement in the x-axis direction:
Movement amount in x, y axis directions: movement amount in y, z axis directions: z
Only the position changed. Here, the amount of parallel movement is different from rotation, and the order of X, Y, Z movement does not matter.

Now, consider a circle having a radius of 1 as a target Object. Here, it is assumed that the circle is formed around the origin (0, 0, 0) on the XY plane. If this is defined as the reference posture, the posture at the beginning or the posture of the circle is not changed.
Assuming that the “circle” with the determined posture is arranged in the space in this way, the spatial degrees of freedom are θ _x , θ _y , X, Y, Z
The five.

(2) Projection of Ring on Plane When a circle is placed in space as described above, when the circle is observed from a fixed point (or reference point 4), it is recognized as an ellipse (telecentric optical system) = Assuming that observations were made at a constant size regardless of distance).

Here, under the assumption that the telecentricity is constant regardless of the distance, the sign of rotation about an axis horizontal to the observation plane cannot be determined, as shown in FIG. For example, the observed image is the same when rotated 45 degrees around the x axis (FIG. 7A) and when rotated 45 degrees around the x axis (FIG. 7B).

However, actual observation uses a non-telecentric optical system, and under such circumstances, an asymmetric component appears with respect to the center of the ring. Here, when considering the diameter passing through the center where the length from the center is the minimum, this diameter is the length divided at the center point, A, B as shown in FIG.
By determining the length of, the sign of the rotation becomes apparent. In FIG. 8, if A <B, the positive direction (FIG.
(A)) On the contrary, if B <A, the direction is negative (FIG. 8 (B)).
Can be easily determined.

Now, it is assumed that the observation point is on the z-axis and the center of the circle is at the origin O. That is, the observation is considered to be a projection shape on the XY plane. When a circle is expressed as x = cos θ and y = sin θ, when the circle is rotated by α around the x axis,

(Equation 1) In the XY plane, an equation of an ellipse having a diameter of 1 and a minor axis is observed (see FIG. 1).

Although it is clear that the shape itself does not change even if it rotates β around the z-axis, it is shown as Equation 2 below. That is, the ellipse of diameter 1 and minor axis cosα (= A) is β
It is a rotated one.

(Equation 2) The above shows that a circular shape is observed as an elliptical shape by taking a free attitude in space. Next, consider detecting a posture from the detected ellipse. However, as is clear from Equation 2, the condition that the surface of the circle is visible (−π / 2
Also, cos α cannot be completely determined because it has two solutions.

The range is limited to 0 to π / 2, and the center of gravity of the image is O (ox, oy) as observation values, and two points are a1: (a1x, aly) and a2: (a2
x, a2y) and the minor axis are b1: (b1x, b1y) and b2: (b2x, b2y).

The ellipse observed under this condition is obtained by moving the original ring around the x-axis.

(Equation 3) Rotate around the z axis

(Equation 4) It is rotated and moved by ox and oy (see Fig. 2).

The above can be obtained from the observed image.

(3) Observation Image of Ring Containing Z Distance Characteristics Up to this point, the description has been simplified by performing telecentric observation. On the other hand, let us consider a condition in which observation is performed with an optical system in which a circle having a known radius (= 1) appears smaller as the distance increases. The coordinate value is x,
When considering an observation system in which y becomes coordinate values (x / F, y / F), the observed image is expressed as follows.

X = (1 / (sin α · sin θ + Z) · k) cos θ y = (1 / (sin α · sin θ + Z) · k) cos α · sin θ In this image, the value when θ = 0 is the diameter / 2 length It is. That is, x = 1 / Zk, and the length simply depends on only the distance of the center of the circle in the z direction. here,

It is assumed that F = (distance from (CCD) to luminescent spot) · k. On the other hand, it cannot be obtained directly from the observation of the minor axis of the observed image, but from the equation, when θ = π / 2, the shortest distance from the origin is (1 / (Z + sinα) · k). (1 / (Z−sin α) · k), and the distance of the minor axis of the ellipse is observed to be asymmetric due to the inclination in the z direction.

(4) Estimation of Spatial Position and Orientation of Ring from Observed Image A method for obtaining the distance and orientation to the origin of a circle having a radius of 1 having the center of the circle on the z-axis by reversing the above discussion. Is shown below.

In the following, the radius of the circle is defined as 1.
The spread of the angle of view for observation is k. Further, the direction from the observation center to the center of the circle is defined as the z-axis. Therefore, the center of the circle is (0, 0) on the observed XY coordinates. For this purpose, the center of the circle has to be recognized in some other way, but here the center of the circle is recognized from an auxiliary marker as shown in FIG.

Search for Angle of Line Segment Corresponding to Longer Diameter Here, two methods are conceivable. One is a method in which the direction perpendicular to the image of the minor axis is defined as the diameter. -1 The distance from the origin to each point of the image is obtained. The line passing through the origin at a right angle to the shortest angle and the image corresponding to the diameter. And

-2 The brightness distribution of the observed image is examined using a straight line passing through the origin as a window (two brightness concentration points are gathered). The distance from the origin to the obtained two points becomes the same (the difference is the minimum or the ratio). Is closest to 1), the angle of the straight window is defined as an image corresponding to the diameter. The angle obtained here is the amount of rotation about the z-axis.

The distance L on the observed image between the two luminance centers on the major axis is obtained. This L is: L = 1 / ZK,
Thereby, the distance Z from the observation center to the center is obtained.

Two luminance centers are obtained for a straight window perpendicular to the major axis. Assuming that the respective distances are i and j (the larger one is i), the rotation θ _x = α around the x-axis is obtained by obtaining the inverse function of ikZ = iksin α + cos α.

FIG. 9 shows an outline of the principle of measurement by the navigation device 1 of the present invention described above by a flow.

[0043]

FIG. 3 shows an example of the creation of a disc-shaped index 3 used in the present invention. The disc-shaped indicator 3 includes a ring-shaped indicator (ring) 3a composed of a light emitter, a color pattern, and the like. As described above, when this index is captured by the CCD camera 5 or the like, it is observed as an ellipse as shown in FIG. 4 depending on the angle with the CCD camera 5, but the length of its major axis is Independently, it indicates distance information to the CCD camera 5.

The disc-shaped index 3 includes a center position index section 3b which is a center position marker for accurately calculating the center of the ring, and a rotation angle index which is an auxiliary index of a small circle representing the rotation angle information of the ring. A portion 3c is provided. These indices and auxiliary indices can also be created by applying a fluorescent paint or a high-brightness paint on a black disk, but if higher stability is required, the indices and auxiliary indices should be LED lighted. Consist of body.

FIG. 5 shows a navigation in which the above-mentioned disc-shaped index 3 is fixed to a probe 2 for determining a surgical position, which is an operation target, and an image of the index is taken by a CCD camera 5 installed at the tip of an articulated arm 8. 1 shows a configuration example of a system.
By miniaturizing the arm part of this articulated arm 8,
It is also possible to configure a navigation system for endoscopic surgery. In this case, the disc-shaped indicator 3 is small enough to be inserted into the abdominal cavity, and the probe 2 is shaped so that one end can be grasped and operated from outside the body as shown in FIG. The opening angle at each joint of the articulated arm 8 is read by a rotary encoder (not shown). Then, the three-dimensional position of the CCD camera 5 is measured by determining the opening of each joint.

The CCD camera 5 installed at the tip of the articulated arm 8 is changed to a surgical microscope, and the three-dimensional position of the disc-shaped index 3 is measured from the image signal. By inputting the position and orientation to the coordinate conversion device, navigation under a microscope can be realized.

The information read by the CCD camera 5 is processed by the image processing device 6. As shown in FIG. 5, the image processing device 6 performs processing such as image capture, noise processing, distortion correction, search for a symmetric shape, and calculation of distance and posture, and calculates the viewpoint distance and posture of the probe 2. .

The image from the CCD camera 5 is displayed on the image display unit 7. For example, in this embodiment, as shown in FIG. 6, a CRT 7a for displaying a video signal from the CCD camera 5 and a CRT 7b for displaying an image synthesized with another image (for example, a tomographic image of the brain) in the coordinate transformation device 9.
Different images are displayed on the two monitors.

As described above, according to the navigation apparatus 1 of the present embodiment, when constructing the optical navigation system for surgery, the number of CCD cameras 5 conventionally required at least two may be reduced to one. It becomes possible. As a result, the geometrical dimensions of the light receiving unit conventionally required several hundred mm, but can be realized with the diameter of one CCD camera. Therefore, during endoscopic surgery, a diameter of 1
Optical navigation using a CCD camera of about 0 mm can be realized.

The above embodiment is an example of a preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the spirit of the present invention. For example, in the present embodiment, the case where one reference point 4 is provided in the space has been described. However, this is not necessarily one camera. Even when a plurality of cameras are used, if the cameras are sequentially switched and used, the reference point 4 is still one point. according to this,
For example, in a case where blind spots occur during movement with only one camera, it is possible to prevent intermittent measurement data by switching cameras.

In this specification, the disc-shaped index 3 or the disc-shaped index 3 and the annular index portion 3 on the disc-shaped index 3 are used.
Although the case of performing navigation based on a combination of a and the like has been described, these are only one form of the index, and the disc-shaped index referred to in this specification includes all indices that can be recognized as at least the outer circumference being circular (for example, (A rectangular plate with an annular index portion 3a).

[0052]

As is apparent from the above description, according to the navigation device of the first aspect, the disc-shaped index having a known radius is attached to the operation target such as the probe.
Even with a single viewpoint, by taking into account the two-dimensional position of the observed image in the field of view and the information obtained from the flatness of the image observed as an ellipse, the three-dimensional position of the probe and Posture can be estimated.

This makes it possible to configure a navigation device with a single camera. In particular, during an operation such as a neurosurgery, the surgeon can operate the patient's operation site and CT.
For example, it is possible to grasp the positional relationship between tomographic images such as a tomographic image and to achieve space saving and cost saving.

According to the navigation method of the present invention, since the disc-shaped index is projected by the movement reference point at which the coordinates of the reference point can be grasped, the disc-shaped index is followed while following the movement of the moving operation target. Can be projected.

According to the third aspect of the present invention, the center position is obtained by the center position index portion indicating the center of the disc-shaped index, and the major axis length and the minor axis length of the ellipse are determined based on the center position. it can. Therefore, the center position can be easily obtained, and the intersection of the long axis and the short axis can be reliably recognized.

According to the navigation method of the fourth aspect, it is possible to easily determine how much the image of the disk-shaped index is rotated around the reading axis by the asymmetrically provided rotation angle index unit. Further, by determining whether the surface of the disc-shaped index is closer or farther from the center of the disc-shaped index, it is easy to recognize which direction the surface of the disc-shaped index is inclined.

According to the navigation apparatus of the fifth aspect of the present invention, since the disc-shaped index having a known radius is attached to the operation target, when the image of the operation target is observed by the monocular camera, the observation point (reference The distance from the point to the disc-shaped index can be calculated. Also, by taking into account the information obtained from the two-dimensional position of the observed image in the field of view and the flatness of the ring image observed as an ellipse, the three-dimensional position and orientation of the operation target are estimated. it can. This makes it possible to configure a navigation device with a single camera, and particularly in the case of surgery such as neurosurgery, an operator can grasp the positional relationship between a surgical operation site of a patient and a tomographic image such as CT. And space saving and cost saving are achieved.

According to a sixth aspect of the present invention, in the navigation device, the image reading means can be moved while grasping the coordinates of the reference point.
Since a CD camera is used, the disc-shaped index can be projected while following the movement of the moving operation target.

According to the seventh aspect of the present invention, since the circular index portion made of a luminous body or a color pattern is provided on the disc-shaped index, an easily recognizable elliptical image is created, and the viewpoint distance and the posture are calculated. Accuracy can be improved.

Further, since the navigation device according to the eighth aspect is provided with the center position index portion indicating the center position of the disc-shaped index, the major axis length and the minor axis length of the ellipse are obtained based on the center position, and the major axis and the minor axis are determined. The intersection of the axes can be recognized reliably and easily.

According to the ninth aspect of the present invention, since the asymmetric rotation angle index portion indicating the amount of rotation of the operation target object about the reading axis is provided at a position other than the center position of the disk-shaped index, the circumferential position of the recognition means is provided. Is detected, the rotation amount of the operation target can be easily obtained.

[Brief description of the drawings]

FIG. 1 shows a ring in a plane rotated by α around the x-axis.

FIG. 2 is a diagram showing an elliptical image rotated by β around the z axis.

FIG. 3 shows an annular index portion, a center position index portion on a disc-shaped index,
It is a figure showing the example of shape of a rotation angle indicator.

FIG. 4 is a diagram showing a state where the annular index portion shown in FIG. 3 is viewed obliquely.

FIG. 5 is a diagram showing an example of a system configuration of a navigation device using a disc-shaped index.

FIG. 6 is a diagram showing an example of a system construction of a navigation device for an endoscope.

FIG. 7 is a diagram showing an observed image under the assumption of a telecentric optical system.

FIG. 8 is a diagram illustrating an example of an observation image in a normal optical system.

FIG. 9 is a flowchart showing an outline of a measurement principle by the navigation device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Navigation apparatus 2 Probe (operation target) 3 Disc-shaped index 3a Ring-shaped index part 3b Center position index part 3c Rotation angle index part 4 Reference point 5 CCD camera (image reading means) 6 Image processing device 7 Image display part

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Haruhiro Tsuneda 6100 Uehara, Ina-shi, Nagano Prefecture Sankyo Seiki Seisakusho Ina Plant (72) Inventor Masao Yajima 6100 Uehara, Ina-shi Nagano Prefecture Sankyo Seiki Seisakusho Co., Ltd. Inside the Ina Plant (72) Inventor Yukio Kosugi 1-2-16 Higashi Tamagawa, Setagaya-ku, Tokyo (72) Inventor Hidetoshi Watanabe 5-29-12-1001, Hongo, Bunkyo-ku, Tokyo

Claims (9)

[Claims] 1. A navigation method for recognizing a current position of an operation target based on three-dimensional coordinates set in a space and assisting in guiding the operation target to a desired position.
The disk-shaped index provided integrally with the operation target is projected from a certain reference point in space, and a flat image of an ellipse or a perfect circle having a different flattening rate depending on a reading angle, and based on a major axis length of the ellipse, A navigation method comprising: obtaining a distance from a reference point to the disc-shaped index; and obtaining an inclination angle of the disc-shaped index based on a major axis length and a minor axis length of the ellipse. 2. The navigation method according to claim 1, wherein the disc-shaped index is displayed by a movement reference point at which coordinates of the reference point can be grasped. 3. The elliptical ellipse according to claim 1, wherein a center position is obtained by a center position index unit indicating a center of the disc-shaped index, and a long axis length and a short axis length of the ellipse are obtained based on the center position. 2. The navigation method according to 2. 4. The navigation method according to claim 1, wherein an amount of rotation of the operation target object around the reading axis is obtained by an asymmetric rotation angle indicator provided at a position other than the center. 5. A navigation device for recognizing a current position of an operation target based on three-dimensional coordinates set in a space and assisting in guiding the operation target to a desired position.
A disc-shaped index which is an index provided integrally with the operation target and which is image-recognized as an ellipse having a different flatness according to a reading direction, and an ellipse or true which is obtained by projecting the disc-shaped index from a certain reference point in space. Image reading means for obtaining a plane image of a circle, and determining the distance from the reference point to the disc-shaped index based on the major axis length of the ellipse and the disc shape based on the major axis length and minor axis length of the ellipse A navigation device comprising: an image processing device that calculates an inclination angle of an index. 6. The navigation apparatus according to claim 5, wherein said image reading means is a CCD camera movable while grasping the coordinates of said reference point. 7. The navigation device according to claim 5, wherein an annular index portion made of a luminous body or a color pattern is provided on the disc-shaped index. 8. The navigation device according to claim 5, further comprising a center position index indicating a center position of the disc-shaped index. 9. The apparatus according to claim 5, further comprising an asymmetrical rotation angle indicator indicating an amount of rotation of the operation target object about the reading axis, provided at a position other than the center position of the disk-shaped indicator. A navigation device as described.