A method for osteotomy trajectory planning of surgical robots

Abstract

The present invention discloses a method for planning osteotomy trajectories for a surgical robot, comprising the following steps: S1, obtaining a preoperative image of the patient's affected area, segmenting the image of the vertebra to be cut, and planning an osteotomy plane on the preoperative image accordingly; S2, registering the preoperative image with the intraoperative image, performing an intersection operation on the planned osteotomy plane and the point cloud in the image of the vertebra to be cut, and obtaining a limiting boundary and a safety boundary of the vertebra to be cut in the intraoperative image; S3, smoothing the limiting boundary of the vertebra to be cut obtained in S2; S4, calculating the normal vector of each point on the smoothed limiting boundary in S3, and combining S3 to obtain an ultrasonic scalpel motion planning trajectory. The present invention can obtain a smooth planning trajectory, ensure that the cutting direction is always perpendicular to the surface of the patient's lesion, and ensure that the cutting plane is cut neatly.

Description

Technical Field

[0001] The present invention relates to the technical field of surgical robots, and in particular to an osteotomy trajectory planning method for a surgical robot. Background Art

[0002] Spinal decompression surgery robots are primarily used for procedures such as laminectomy and laminoplasty for conditions like ligamentum flavum solidification and spinal stenosis. Compared to traditional medical procedures, they offer more precise cutting and greater safety for surrounding tissues. Research is underway in medical institutions both domestically and internationally. Robotic spinal decompression surgery involves image acquisition, image segmentation, surgical planning, registration, and navigation. Constraining the cutting plane for the robotic arm is crucial, but currently, due to the lack of visibility into the spinal canal, there is a risk of overcutting, potentially damaging vital organs like the spinal cord. Furthermore, the cutting process can be uneven and time-consuming. Summary of the Invention

[0003] Purpose of the invention: In view of the above-mentioned shortcomings, the present invention provides a method for planning osteotomy trajectories of a surgical robot, which can obtain a smooth planned trajectory, ensure that the cutting direction is always perpendicular to the surface of the patient's lesion, and ensure that the cutting plane is cut neatly.

[0004] Technical solution:

[0005] The present invention provides a method for planning osteotomy trajectories of a surgical robot, comprising:

[0006] S1. Obtain preoperative images of the patient's affected area, segment the images of the vertebrae to be cut, and plan the osteotomy plane based on the images;

[0007] S2. Registering the preoperative image and the intraoperative image, performing an intersection operation on the planned osteotomy plane and the point cloud in the image of the vertebra to be cut, and obtaining the limiting boundary and safety boundary of the vertebra to be cut in the intraoperative image;

[0008] S3, smoothing the restricted boundary of the vertebral segment to be cut obtained in S2;

[0009] S4: Calculate the normal vector of each point on the restricted boundary after smoothing in S3, and combine it with S3 to obtain the ultrasonic knife motion planning trajectory.

[0010] Specifically, the S2 is:

[0011] Specifically, the S2 is:

[0012] Horizontal simulation lines are set at equal intervals between the two corner points in the vertical direction of the planning frame formed by the osteotomy plane. Two intersection points are generated between each simulation line and the vertebra to be cut. The intersection point close to the vertebra is the restriction point, and the intersection point far from the vertebra is the safety point. Sub-pixel interpolation is performed on the corresponding safety points and restriction points to obtain the safety boundary and restriction boundary composed of the corresponding discrete point sets.

[0013] Specifically, the S3 is:

[0014] calculating an intersection line between the osteotomy plane and the patient's coronal plane;

[0015] Construct a smoothed limiting boundary curve function, substitute all points in the corresponding discrete point set, calculate the parameters of the limiting boundary curve function, thereby obtaining a smoothed limiting boundary curve function, and further obtaining a smoothed limiting boundary.

[0016] More specifically, the limit boundary curve function obtained by the constructed smoothing process is as follows:

[0017] x=a0+a1*(t-t0)+a2*(t-t0) 2 +a3*(t-t0) 3

[0018] y=b0+b1*(t-t0)+b2*(t-t0) 2 +b3*(t-t0) 3

[0019] z=c0+c1*(t-t0)+c2*(t-t0) 2 +c3*(t-t0) 3

[0020] Wherein, x, y, and z are the distances between a point in the limiting boundary curve obtained by smoothing and the patient's coronal plane, sagittal plane, and transverse plane, respectively; a0, a1, a2, a3, b0, b1, b2, b3, c0, c1, c2, and c3 are function parameters, respectively; t is the distance between a point in the limiting boundary curve obtained by smoothing and the intersection line, t∈[t0,t1], t0 is the distance between the starting point of the limiting boundary of the vertebral segment to be cut and the intersection line, and t1 is the distance between the ending point of the limiting boundary of the vertebral segment to be cut and the intersection line.

[0021] Specifically, in S3, the limiting boundary of the vertebral segment to be cut obtained in S2 is smoothed by using an interpolation method.

[0022] Specifically, in S4, the normal vector of each point on the restricted boundary after smoothing in S3 is as follows:

[0023] Get a point on the restricted boundary and its front and back points, get the vector between two adjacent points and its modulus respectively, thereby getting the normal vector of the front and back points corresponding to the point, and then perform weight distribution according to the aforementioned modulus length to get the normal vector of the point.

[0024] More specifically, the weight distribution based on the aforementioned modulus length is used to obtain the normal vector of a point on the restricted boundary, specifically:

[0025]

[0026] in:

[0027]

[0028] d0=‖v0‖

[0029] d1=‖v1‖

[0030]

[0031] Where p1, p0, and p2 are a point on the limit boundary and its front and back points, v0 and v1 are the vectors between two adjacent points, d0 and d1 are the moduli of vectors v0 and v1, V0 and V1 are the normal vectors of the front and back points p0 and p2 of point p1, respectively. l is the direction vector of the intersection line l between the osteotomy plane and the patient's coronal plane.

[0032] Specifically, after obtaining the safe boundary of the vertebral segment to be cut in the intraoperative image in S2, it is smoothed in S3.

[0033] Specifically, in S1, the vertebral segment image in the preoperative image is obtained through AI vertebral segment semantic segmentation.

[0034] Beneficial effects: The present invention fully considers the restriction boundary, safety boundary and plane constraint, and obtains the ultrasonic knife motion planning trajectory in combination with the normal vector of each point on the restriction boundary, thereby obtaining a smooth planning trajectory, ensuring that the cutting direction is always perpendicular to the patient's lesion surface, ensuring that the cutting plane is cut neatly, and through the set safety boundary to avoid damage to important organs such as the spinal cord. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 A flow chart of the trajectory planning method of the present invention;

[0037] Figure 2 An example diagram of trajectory planning of the present invention;

[0038] Figure 3 An example diagram for obtaining the limiting boundary and safety boundary of the vertebra to be cut in the osteotomy plane. DETAILED DESCRIPTION

[0039] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present application is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0040] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of the present invention should have the usual meanings understood by persons with ordinary skills in the field to which the present invention belongs. "Include" or "comprising" and similar words mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0041] In a surgical robot such as a spinal decompression surgical robot, after obtaining preoperative images of the patient's affected area, the image is segmented to obtain vertebral images therein, and preoperative cutting plane planning is performed on the segmented vertebral images, and then a rough restriction boundary and a safety boundary trajectory are generated along the planned cutting plane. The rough restriction boundary trajectory is smoothed by the algorithm of the present invention to generate a fine restriction boundary trajectory, that is, the planned osteotomy trajectory. The planned osteotomy trajectory is registered to the intraoperative image, and the surgical robot is navigated accordingly. The initial safe position of the ultrasonic scalpel installed on the end of the surgical robot's robotic arm can be obtained by lifting a certain distance from the restriction boundary of the planned osteotomy trajectory. Based on this, the surgical robot navigates the movement of its robotic arm so that the ultrasonic scalpel installed on the end of its robotic arm moves to the initial safe position, and then turns on the corresponding control. The doctor freely drags the ultrasonic scalpel to cut between the restriction boundary and the safety boundary of the planned osteotomy trajectory under the constraints of the aforementioned planned plane, and turns off the control after completing the cutting task. Among them, when the ultrasonic bone knife reaches near the safety boundary, the system determines whether to stop cutting based on the impedance value of the ultrasonic bone knife, and cooperates with the interface to display the feed amount and surgical process in real time to ensure that the osteotomy process is safe and controllable, ensure the success rate of the operation, and avoid unnecessary risks.

[0042] Specifically, in the present invention, the osteotomy trajectory planning method of the surgical robot is as follows: Figure 1 As shown, the steps include:

[0043] S1. Obtain preoperative images of the patient's affected area, segment the images of the vertebrae to be cut, and plan the osteotomy plane based on the images;

[0044] In the present invention, the vertebral segment images in the preoperative images of the patient's affected part can be obtained through AI vertebral segment semantic segmentation; specifically, the U-Net network adaptive image segmentation framework can be used.

[0045] In the present invention, based on the segmented image of the vertebra to be cut, the ultrasonic scalpel's operating plane is planned on the preoperative image as the osteotomy plane.

[0046] In the present invention, the preoperative images are CT images.

[0047] S2. Registering the preoperative image and the intraoperative image, performing an intersection operation on the planned osteotomy plane and the point cloud in the image of the vertebra to be cut, and obtaining the limiting boundary and safety boundary of the vertebra to be cut in the intraoperative image;

[0048] Based on the image of the vertebra to be cut obtained by S1, the doctor plans the ultrasonic knife operation plane on the preoperative image, and uses it as the osteotomy plane. The planned osteotomy plane is intersected with the point cloud in the image of the vertebra to be cut to obtain the two boundaries where the osteotomy plane and the vertebra to be cut intersect. Among them, the boundary closer to the vertebra is the limiting boundary (such as Figure 2 、 3 The middle A line) may enter the medullary cavity, nerves, blood vessels and other dangerous areas, and continuous action will cause damage to them; the other is the safe boundary (such as Figure 2 、 3 The middle B line) enters the bone area of ​​the vertebra from here, generating cutting force changes; the area between the two is the cutting area of ​​the ultrasonic scalpel. The ultrasonic scalpel acts on the two degrees of freedom of movement in the osteotomy plane, and can move forward or sink. The other four degrees of freedom constraints cannot be executed, such as Figure 2 、 3 shown.

[0049] In the present invention, the planned osteotomy plane P can be obtained by an inner point and its normal vector N P For example, the inner point of the osteotomy plane P can be represented by the four corner points p of the planned osteotomy plane P. t0 、p t1 、p t2 、p t3 Any of the following expressions: Figure 3 shown.

[0050] In the present invention, the limiting boundary and the safety boundary of the vertebra to be cut in the osteotomy plane in the intraoperative image are obtained as follows: Figure 3 As shown, specifically:

[0051] After registration, the two corner points in the vertical direction of the planning frame formed by the osteotomy plane planned by the doctor are as follows: Figure 3 The corner point p in t0 、p t1 According to the set step size, horizontal simulation lines are set at equal intervals, such as the horizontal straight lines in the figure. In the present invention, they can also be perpendicular to the direction of the spine; two intersections are generated between each simulation line and the vertebra to be cut, the intersection close to the vertebra is the restriction point, and the intersection far from the vertebra is the safety point. The corresponding safety points and restriction points are respectively interpolated by sub-pixel, so as to obtain a point set consisting of the extracted points and the interpolated points, which are respectively used as the safety boundary point set and the restriction boundary point set, thereby obtaining the safety boundary and the restriction boundary.

[0052] In this embodiment, Figure 3 As shown, the two corner points in the vertical direction of the planning frame are p t0 、p t1 , set the horizontal simulation lines at equal intervals, then we can get p t0 With p t2 The points on the safety boundary and the points on the restriction boundary are p s0 and p s1 , p t1 With p t3 The points on the safety boundary and the points on the restriction boundary are p s2 and p s3 , and then get the rough safety boundary and restriction boundary, respectively Figure 3 The yellow boundary saftyBoundray and the red boundary LimitBoundray are shown in the figure, where the yellow boundary, i.e. line B, is the safe boundary, and the red boundary, i.e. line A, is the limit boundary.

[0053] S3, smoothing the limiting boundary of the vertebra to be cut in the osteotomy plane obtained in S2 to obtain a fine limiting boundary of the osteotomy plane;

[0054] The limiting boundary of the vertebra to be cut in the osteotomy plane obtained by S2 is a discontinuous boundary composed of discrete points, wherein the point set composed of discrete points is set to G. The present invention performs smoothing processing on it based on this. By smoothing the safety, the osteotomy trajectory is made more refined, and the operation of the ultrasonic knife is made smoother to prevent the ultrasonic knife from shaking.

[0055] Specifically, the limiting boundary of the vertebra to be cut in the osteotomy plane obtained by S2 is smoothed by cubic spline interpolation as follows:

[0056] During the operation, the patient is in a prone position, and the direction of the ultrasonic scalpel is always toward the patient's coronal plane, thereby calculating the intersection line l between the osteotomy plane obtained by S2 and the patient's coronal plane.

[0057] The limit boundary curve function obtained by smoothing is constructed as follows:

[0058] x=a0+a1*(t-t0)+a2*(t-t0) 2 +a3*(t-t0) 3

[0059] y=b0+b1*(t-t0)+b2*(t-t0) 2 +b3*(t-t0) 3

[0060] z=c0+c1*(t-t0)+c2*(t-t0) 2 +c3*(t-t0) 3

[0061] Where x, y, and z are the distances between a point in the smoothed limiting boundary curve and the patient's coronal, sagittal, and transverse planes, respectively; a0, a1, a2, a3, b0, b1, b2, b3, c0, c1, c2, and c3 are function parameters, and t0 is the distance between the starting point of the limiting boundary of the vertebra to be cut in the osteotomy plane obtained by S2 and the intersection line l. In this example, Figure 3 The corner point p in t2 The distance between the intersection line l; t is the distance between a point in the limit boundary curve obtained by smoothing and the intersection line l, t1 is the distance between the end point of the limit boundary of the vertebra to be cut in the osteotomy plane obtained by S2 and the intersection line l, t∈[t0,t1];

[0062] Substituting all points in the point set G into the aforementioned formula, the aforementioned function parameters can be calculated, thereby obtaining a smoothed limiting boundary curve function, and further obtaining a precise safety boundary of the osteotomy plane. There are many methods for smoothing boundaries, such as line interpolation and cubic spline interpolation. This embodiment only uses cubic spline interpolation as an example.

[0063] In the present invention, in the image, the left-right direction of the human body is the x-axis, the front-back direction of the human body is the y-axis, and the head-foot direction of the human body is the z-axis to establish an image coordinate system, and the patient's coronal plane, sagittal plane, and transverse plane are yoz, xoz, and xoy planes respectively.

[0064] S4, calculating the normal vector of each point on the restricted boundary of the osteotomy plane obtained in S3, and obtaining the ultrasonic scalpel motion planning trajectory in combination with the restricted boundary of the osteotomy plane obtained in S3;

[0065] Specifically, a point on the restricted boundary and its front and rear points are obtained, and the vector between two adjacent points and its modulus are obtained respectively, thereby obtaining the normal vector of the front and rear points corresponding to the point. Based on this, the weight distribution is performed according to the aforementioned modulus length to obtain the normal vector of the point, and the restricted boundary of the osteotomy plane obtained by S3 is combined to obtain the ultrasonic knife motion planning trajectory.

[0066] Specifically, obtain a point p1 on the restricted boundary and its preceding and following points p0 and p2, and calculate the vectors v0 and v1 between the two adjacent points and their moduli d0 and d1 respectively. Thus, the normal vectors V0 and V1 of the preceding and following points p0 and p2 of point p1 are calculated. The normal vector of point p1 is obtained by weighting according to the aforementioned modulus length:

[0067]

[0068] in:

[0069]

[0070] d0=‖v0‖

[0071] d1=‖v1‖

[0072]

[0073] Where N l is the direction vector of the intersection line l.

[0074] In the present invention, the starting point of the safety boundary of the vertebra to be cut obtained by S2 is used as the starting position of the ultrasonic knife cutting. The starting position of the ultrasonic knife cutting is raised to a set height along the height direction of the osteotomy plane to obtain the initial safety position of the ultrasonic knife to ensure that it does not collide with the spinous process bone, surrounding surgical instruments, etc. The robot navigation system controls the ultrasonic scalpel to move to the initial safe position of the ultrasonic scalpel, and then descends to the set height to the starting position for cutting. The doctor cuts the vertebra to be cut under force-controlled dragging, and cuts to the limit boundary. The ultrasonic scalpel is controlled to cut with the ultrasonic scalpel motion planning trajectory obtained by S4. During the cutting process, the robot navigation system obtains the current position of the ultrasonic scalpel in real time, and determines whether the current position of the ultrasonic scalpel exceeds the range of the osteotomy plane and whether it is close to the set range of the safety boundary of the osteotomy plane obtained by S2. If the current position of the ultrasonic scalpel exceeds the range of the osteotomy plane, a reaction force is applied to the ultrasonic scalpel to drive it into the range of the osteotomy plane. If the current position of the ultrasonic scalpel is close to the set range of the safety boundary of the osteotomy plane obtained by S2, it needs to be more finely controlled. In the present invention, admittance compliance control can be adopted, wherein the admittance compliance control can adopt existing technology, which will not be repeated here.

[0075] In the present invention, after the safety boundary of the osteotomy plane is obtained in S2, it can also be smoothed in S3 to make the control more precise.

[0076] The trajectory planning method of the present invention fully considers the safety boundary, restriction boundary and plane constraint, and determines the initial safe posture of the ultrasonic knife based on the safety boundary. It can also perform smoothing based on the restriction boundary to obtain a complete and smooth restriction boundary, and combine the normal vectors of the positions of each point on the restriction boundary to obtain the ultrasonic knife motion planning trajectory, so as to obtain a smooth planning trajectory, ensure that the cutting direction is always perpendicular to the patient's lesion surface, and ensure that the cutting plane is cut neatly to avoid damage to important organs such as the spinal cord.

[0077] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention (including the claims) is limited to these examples. Within the scope of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the embodiments of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0078] The embodiments of the present invention are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for planning osteotomy trajectory of a surgical robot, characterized in that: include: S1. Obtain preoperative images of the patient's affected area, segment the images of the vertebrae to be cut, and plan the osteotomy plane based on the images; S2. Align the preoperative image with the intraoperative image. Set horizontal simulation lines at equal intervals between the two corner points in the vertical direction of the planning frame formed by the osteotomy plane. Generate two intersection points between each simulation line and the vertebra to be cut. The intersection point close to the vertebra is the restriction point, and the intersection point far from the vertebra is the safety point. Sub-pixel interpolation is performed on the corresponding safety points and restriction points to obtain the safety boundary and restriction boundary composed of the corresponding discrete point sets, that is, the restriction boundary and safety boundary of the vertebra to be cut in the intraoperative image. S3. Calculating the intersection line between the osteotomy plane and the coronal plane of the patient, constructing a smoothed limiting boundary curve function, substituting all points in the corresponding discrete point set into the function, calculating parameters of the limiting boundary curve function, thereby obtaining a smoothed limiting boundary curve function, and further obtaining a smoothed limiting boundary; S4: Calculate the normal vector of each point on the restricted boundary after smoothing in S3, and combine it with S3 to obtain the ultrasonic knife motion planning trajectory.

2. The osteotomy trajectory planning method of a surgical robot according to claim 1, characterized in that: The limit boundary curve function obtained by the smoothing process is as follows: x=a0+a1(t-t0)+a2(t-t0) 2 +a3(t-t0) 3 y=b0+b1(t-t0)+b2(t-t0) 2 +b3(t-t0) 3 z=c0+c1(t-t0)+c2(t-t0) 2 +c3(t-t0) 3 Wherein, x, y, and z are the distances between a point in the smoothed limiting boundary curve and the patient's coronal plane, sagittal plane, and transverse plane, respectively; a0, a1, a2, a3, b0, b1, b2, b3, c0, c1, c2, and c3 are function parameters, respectively; t is the distance between a point in the smoothed limiting boundary curve and the intersection line, t∈[t0, t1], t0 is the distance between the starting point of the limiting boundary of the vertebral segment to be resected and the intersection line, and t1 is the distance between the ending point of the limiting boundary of the vertebral segment to be resected and the intersection line.

3. The osteotomy trajectory planning method of a surgical robot according to claim 1, characterized in that: In S3, the limiting boundary of the vertebral segment to be cut obtained in S2 is smoothed by using an interpolation method.

4. The osteotomy trajectory planning method of a surgical robot according to claim 1, characterized in that: In S4, the normal vector of each point on the restricted boundary after smoothing in S3 is as follows: Get a point on the restricted boundary and its front and back points, get the vector between two adjacent points and its modulus respectively, thereby getting the normal vector of the front and back points corresponding to the point, and then perform weight distribution according to the aforementioned modulus to get the normal vector of the point.

5. The osteotomy trajectory planning method of a surgical robot according to claim 4, characterized in that: The weight distribution according to the aforementioned modulus is used to obtain the normal vector of a certain point on the restricted boundary, specifically: ； in: ； ； ； ； ； ； Where p1, p0, and p2 are a point on the limit boundary and its front and back points, v0 and v1 are the vectors between two adjacent points, d0 and d1 are the moduli of vectors v0 and v1, V0 and V1 are the normal vectors of the front and back points p0 and p2 of point p1, respectively. l is the direction vector of the intersection line l between the osteotomy plane and the patient's coronal plane.

6. The osteotomy trajectory planning method of a surgical robot according to claim 1, characterized in that: After obtaining the safe boundary of the vertebral segment to be cut in the intraoperative image in S2, it is smoothed in S3.

7. The osteotomy trajectory planning method of a surgical robot according to claim 1, characterized in that: In S1, the vertebral segment image in the preoperative image is obtained by AI vertebral segment semantic segmentation.

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