A method for calibrating the center position of a surgical navigation locator

Abstract

The present invention discloses a method for calibrating the center position of a surgical navigation locator, and relates to the field of computer-assisted medical technology. The method comprises: moving the end of a robotic arm when the surgical navigation locator is not installed, so that the vertical distance between the end of the robotic arm and the calibration plate is equal to the vertical distance between the central theoretical position of the surgical navigation locator and the end of the robotic arm, so that the current central theoretical position of the surgical navigation locator is at a coordinate position p1 on the calibration plate, and determining the coordinate position p2 of the intersection of the axis of the end of the robotic arm and the calibration plate on the calibration plate at this time; moving the end of the robotic arm so that the central theoretical position of the surgical navigation locator moves from coordinate position p1 to coordinate position p2; converting coordinate position p2 into coordinate position p3 in the camera image. The present invention efficiently, accurately and conveniently solves the problem of positioning the theoretical position when monitoring the center point offset of the surgical navigation locator.

Description

Technical Field

[0001] The present invention relates to the technical field of computer-aided medical treatment, and in particular to a method for calibrating the center position of a surgical navigation locator. Background Art

[0002] The existing surgical navigation locator is installed at the end of the robotic arm, and is used to clamp surgical instruments through the center point and perform positioning navigation during surgery. When the surgical navigation locator is subjected to force, lateral displacement in the X and Z directions will occur, with an offset range of 0-5mm. This displacement will affect the intraoperative positioning accuracy. In order to monitor the position and movement of the surgical navigation locator, it is necessary to calculate the center position error of the surgical navigation locator, and it is also necessary to obtain the theoretical position of the center of the surgical navigation locator, but the existing technology cannot accurately, efficiently, and conveniently determine the theoretical position of the center of the surgical navigation locator. Summary of the invention

[0003] In view of the above-mentioned defects or shortcomings in the prior art, the present invention provides a method for calibrating the center position of a surgical navigation locator. In this method, a monocular camera is fixed to the end of a robotic arm through a tooling, and the theoretical position of the center point of the surgical navigation locator in the camera is calibrated in combination with the camera image and the calibration plate. This method efficiently, accurately and conveniently solves the problem of positioning the theoretical position when monitoring the offset of the center point of the surgical navigation locator.

[0004] The present invention provides a method for calibrating the center position of a surgical navigation locator, comprising the following steps: moving the end of a robotic arm when the surgical navigation locator is not installed, so that the vertical distance between the end of the robotic arm and a calibration plate is equal to the vertical distance between the central theoretical position of the surgical navigation locator and the end of the robotic arm, so that the current central theoretical position of the surgical navigation locator is at a coordinate position p1 on the calibration plate, and determining the coordinate position p2 of the intersection of the axis of the end of the robotic arm and the calibration plate at this time on the calibration plate; moving the end of the robotic arm so that the central theoretical position of the surgical navigation locator moves from the coordinate position p1 to the coordinate position p2; and converting the coordinate position p2 into a coordinate position p3 in a camera image.

[0005] The method for calibrating the center position of a surgical navigation locator provided by the present invention overcomes the defects of the prior art of using large and low-precision sensors to calibrate the center position of a surgical navigation locator, which is inconvenient, low-precision and low-efficiency. A monocular camera is selected as the monitoring device, and an innovative position calibration algorithm is used to realize efficient, accurate and convenient calibration of the theoretical position when monitoring the center point offset of the surgical navigation locator. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 is a schematic diagram of the structure of a surgical navigation and positioning device provided by an embodiment of the present application; Figure 2 It is a flowchart of a method for calibrating the center position of a surgical navigation locator provided by an embodiment of the present application; Figure 3 It is a scene diagram of a method for calibrating the center position of a surgical navigation locator provided in an embodiment of the present application. DETAILED DESCRIPTION

[0007] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0008] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0009] It should be understood that although the terms first, second, third, etc. may be used to describe the acquisition modules in the embodiments of the present invention, the acquisition modules should not be limited to these terms. These terms are only used to distinguish the acquisition modules from each other.

[0010] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0011] It should be noted that the directional words such as "upper", "lower", "left", and "right" described in the embodiments of the present invention are described at the angles shown in the drawings and should not be understood as limiting the embodiments of the present invention. In addition, in the context, it should also be understood that when it is mentioned that an element is formed "on" or "under" another element, it can not only be formed directly "on" or "under" another element, but also be formed "on" or "under" another element indirectly through an intermediate element.

[0012] The invention of this application aims to provide a method for calibrating the center position of a surgical navigation locator, by fixing a monocular camera to the end of a robotic arm through a tooling, and combining the camera image and the calibration plate to calibrate the theoretical position of the center point of the surgical navigation locator in the camera. After accurately obtaining the theoretical position of the center point of the surgical navigation locator in the camera, the position deviation of the surgical navigation locator can be tracked and monitored by comparing the actual position of the center point of the surgical navigation locator.

[0013] Based on the similar working principle of surgical navigation locators, the surgical navigation locator center position calibration method proposed in this application is suitable for all types of surgical navigation locators that clamp surgical instruments through the clamping center point (referred to as the center point) of the surgical navigation locator. Exemplarily, this application takes a double ring locator as an example for detailed description.

[0014] See also Figure 1 The surgical navigation positioning device 100 includes: a mechanical arm 101, a surgical navigation positioning device 102, a monocular camera 103, a first fixing device 104, and a second fixing device 105. The monocular camera 103 is mounted on the end 106 of the mechanical arm through the first fixing device 104, and the surgical navigation positioning device 102 is mounted on the end 106 of the mechanical arm through the second fixing device 105. The axis of the surgical navigation positioning device 102 in the length direction is parallel to the axis of the end of the mechanical arm, and the second fixing device 105 is used to drive the surgical navigation positioning device 102 to move up and down in a direction perpendicular to the axis of the end 106 of the mechanical arm.

[0015] Optionally, the surgical navigation locator 102 is a double-circular ring locator, including a first circular portion 1021, a second circular portion and a line segment portion that can be imaged under medical imaging equipment; wherein, the first circular portion 1021 and the second circular portion are coaxial, the diameter of the first circular portion 1021 is smaller than the diameter of the second circular portion, the line segment portion extends along the radial direction of the first circular portion 1021, and the center of the surgical navigation locator 102 is the center of the first circular portion 1021 or the center of the second circular portion.

[0016] Furthermore, the first fixing device 104 is fixedly connected to the flange 107 , and the flange 107 is fixed to the end 106 of the robot arm.

[0017] Furthermore, the second fixing device 105 is an L-shaped lifting rail, and the L-shaped lifting rail is fixed to the flange 107 .

[0018] The double ring positioner has a design size. Due to factors such as processing errors and stress deformation during use, there is a deviation between the actual position of the clamping center of the double ring positioner and the theoretical position of the clamping center. In order to monitor and calculate this deviation, it is necessary to first accurately calibrate the theoretical position of the center.

[0019] See also Figure 2 An embodiment of the present application provides a method for calibrating the center position of a surgical navigation locator, which uses a monocular camera and a calibration plate to efficiently and accurately calibrate the theoretical center position of a double-ring locator, and specifically includes the following steps: Step S101, move the end of the robotic arm when the surgical navigation locator is not installed, so that the vertical distance between the end of the robotic arm and the calibration plate is equal to the vertical distance between the center theoretical position of the surgical navigation locator and the end of the robotic arm, so that the current center theoretical position of the surgical navigation locator is at the coordinate position p1 on the calibration plate, and determine the coordinate position p2 of the intersection of the axis of the robotic arm end and the calibration plate on the calibration plate.

[0020] See also Figure 3 The method of this embodiment accurately locates the theoretical center position of the surgical navigation locator without installing the surgical navigation locator. Assume that the clamping center of the double ring locator is The axis of the double ring positioner in the length direction is on a straight line parallel to the axis of the end of the robot arm, and the theoretical distance between the two axes is l Known, in addition to the clamping center point Height from the end of the robot arm h Known.

[0021] The calibration process is divided into two stages. The first stage is to move the robotic arm so that the vertical distance between the end of the robotic arm and the calibration plate is equal to the vertical distance between the theoretical center position of the double-ring locator and the end of the robotic arm. The second stage is to find the projection position of the intersection of the axis of the end of the robotic arm and the calibration plate in the camera.

[0022] Phase 1: Move the robotic arm so that the height between the end of the robotic arm and the calibration plate is the theoretical height h In order to move the end of the robot arm to the target position, it can be achieved in the following ways: Step S1011: Use a monocular camera to identify the corner points on the calibration plate and obtain the position and posture of the calibration plate in the camera coordinate system. ; Step S1012: Calculate the initial position of the end of the robot arm in the robot arm base coordinate system based on the initial position of the end of the robot arm and the positional relationship between the end of the robot arm and the robot arm base. ; Step S1013, when the vertical distance between the end of the manipulator and the calibration plate is equal to the vertical distance between the center theoretical position of the double ring locator and the end of the manipulator, the target position of the end of the manipulator in the manipulator base coordinate system is calculated according to the following formula: : (1) in, for The inverse matrix of Indicates the target position of the calibration plate in the end-of-arm coordinate system. is a known quantity; Represents the position and posture of the camera in the coordinate system of the end of the robot arm. is a known quantity; Indicates the position and posture of the calibration plate in the camera coordinate system; Indicates the initial position of the end of the robot arm in the coordinate system of the robot arm base; According to the target position of the end of the manipulator in the manipulator base coordinate system Move the end of the robot arm when the double-ring locator is not installed, so that the current theoretical center position of the double-ring locator is at the coordinate position p1 on the calibration plate.

[0023] The second stage: After the mobile robot is in place, the coordinate position p2 of the intersection of the robot end axis and the calibration plate on the calibration plate is determined. Specifically, it can be found by rotating the robot end. When the robot end rotates, the projection position of the intersection of the robot end axis and the calibration plate in the camera is fixed, so the fixed intersection, that is, the coordinate position p2, can be found by rotating the robot end.

[0024] Specifically include: Step S1014: Use a monocular camera to identify the corner points on the calibration plate and obtain the posture matrix of the calibration plate in the camera coordinate system before the end of the robot arm rotates. and the position matrix , merged into the following pose matrix: (2) in, - It represents the pose matrix parameters of the calibration plate in the camera coordinate system before the end of the manipulator rotates, which is calculated by the monocular camera recognizing the corner points on the calibration plate. Step S1015: Use a monocular camera to identify the corner points on the calibration plate and obtain the posture matrix of the calibration plate in the camera coordinate system after the end of the robotic arm rotates an angle. and the position matrix , merged into the following pose matrix: (3) in, - It represents the pose matrix parameters of the calibration plate in the camera coordinate system after the end of the manipulator rotates an angle, which is calculated by the monocular camera recognizing the corner points on the calibration plate. Step S1016, according to the posture matrix , position matrix , attitude matrix , position matrix and the position matrix of the coordinate position p2 = , calculate the projection coordinates of the coordinate position p2 of the end of the robot before rotation in the camera image: (4) in , is the projection coordinate of the coordinate position p2 before the end of the robot arm rotates in the camera image, is the depth of the coordinate position p2 in the camera image before the end of the robot arm rotates; Step S1017, according to the posture matrix , position matrix , attitude matrix , position matrix and the position matrix of the coordinate position p2 = , calculate the projection coordinates of the coordinate position p2 of the end of the robot after rotation in the camera image: (5) in , is the projection coordinate of the coordinate position p2 of the end of the robot after rotation in the camera image, is the depth of the coordinate position p2 of the end of the robot arm before and after rotation in the camera image; Step S1018: According to the above formulas (4) and (5), we can obtain: (6) in: is the horizontal coordinate of the coordinate position p2, is the ordinate of the coordinate position p2, , , , , , , , , , , , , Solve the above equation (6) to obtain the coordinate value (x, y) of the coordinate position p2.

[0025] Step S102: Move the end of the robotic arm to move the theoretical center position of the surgical navigation locator from the coordinate position p1 to the coordinate position p2.

[0026] Specifically, after obtaining the coordinate position p2 in step S101, the theoretical position of the clamping center of the double-ring locator in the camera image is then searched. l At a distance, and Figure 3 The center point is directly behind the end of the robot arm. Therefore, move the end of the robot arm forward. l After the distance, the coordinate position In short, the theoretical center position of the double ring locator can be moved from coordinate position p1 to coordinate position p2 by moving the end of the robot arm a predetermined distance in the opposite direction of the direction of the double ring locator at the end of the robot arm axis, where the predetermined distance is the vertical distance between the center of the double ring locator and the axis of the end of the robot arm.

[0027] Step S103: convert the coordinate position p2 into a coordinate position p3 in the camera image.

[0028] Specifically, the coordinate position The position of the point in the camera image can be obtained by projecting it onto the camera image. This is achieved through the following steps: Step S1031, after obtaining the coordinate value of the coordinate position p2, the corner points on the calibration plate are identified by a monocular camera to obtain the posture matrix R and position matrix t of the calibration plate in the camera coordinate system; Step S1032, convert the coordinate value (x, y) of the coordinate position p2 to the camera coordinate system according to the following formula:

[0029] in is the coordinate of the coordinate position p2 in the camera coordinate system; Step S1033: Perform normalization to obtain normalized coordinates ; Step S1034, set the camera intrinsic parameter matrix to:

[0030] in, and represents the focal length on the x-axis and y-axis, and represents the origin coordinates of the image coordinate system, , and The quantity is unknown; Step S1035: normalize the coordinates according to the following formula Convert to the pixel coordinate system of the camera image:

[0031] Step S1036, calculate according to the above formula and , get the pixel coordinates of the projection of the theoretical center position of the double ring locator in the camera image , that is, coordinate position p3.

[0032] After calculating the pixel coordinates of the projection of the theoretical center position of the double-ring locator in the camera image (i.e., coordinate position p3), the position offset of the double-ring locator can be tracked and monitored by comparing the actual position of the center point of the double-ring locator. Although the present embodiment is described using the double-ring locator as an example, the method of the present embodiment is not only applicable to the double-ring locator, but also to other surgical navigation locators with a clamping center point, which will not be described in detail in the present embodiment.

[0033] The surgical navigation locator center position calibration method of this embodiment overcomes the defects of the prior art of using large and low-precision sensors to calibrate the center position of the surgical navigation locator, which is inconvenient, low-precision and low-efficiency. A monocular camera is selected as the monitoring device, and an innovative position calibration algorithm is used to achieve efficient, accurate and convenient calibration of the theoretical position when monitoring the center point offset of the surgical navigation locator.

[0034] The above description is only a preferred embodiment of the present invention. Those skilled in the art should understand that the scope of disclosure involved in the present invention is not limited to the technical solution formed by a specific combination of the above technical features, but also should cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above disclosed concept. For example, the above features are replaced with the technical features with similar functions disclosed in the present invention (but not limited to) to form a technical solution.

Claims

1. A method for calibrating the center position of a surgical navigation locator, characterized in that: The steps include: Move the end of the manipulator arm when the surgical navigation locator is not installed, so that the vertical distance between the end of the manipulator arm and the calibration plate is equal to the vertical distance between the center theoretical position of the surgical navigation locator and the end of the manipulator arm, so that the current center theoretical position of the surgical navigation locator is at the coordinate position p1 on the calibration plate, and determine the coordinate position p2 of the intersection of the axis of the end of the manipulator arm and the calibration plate on the calibration plate at this time; Moving the end of the robotic arm to move the theoretical center position of the surgical navigation locator from the coordinate position p1 to the coordinate position p2; The coordinate position p2 is converted to the coordinate position p3 in the camera image.

2. The method for calibrating the center position of a surgical navigation locator according to claim 1, characterized in that: The step of moving the end of the robotic arm when the surgical navigation locator is not installed so that the vertical distance between the end of the robotic arm and the calibration plate is equal to the vertical distance between the central theoretical position of the surgical navigation locator and the end of the robotic arm, thereby making the current central theoretical position of the surgical navigation locator at the coordinate position p1 on the calibration plate comprises: The monocular camera is used to identify the corner points on the calibration plate and obtain the position and posture of the calibration plate in the camera coordinate system. ; The initial position of the end of the robot arm in the robot arm base coordinate system is calculated through the initial position of the end of the robot arm and the position relationship between the end of the robot arm and the robot arm base. ; When the vertical distance between the end of the robotic arm and the calibration plate is equal to the vertical distance between the center theoretical position of the surgical navigation locator and the end of the robotic arm, the target position of the end of the robotic arm in the robotic arm base coordinate system is calculated according to the following formula: : （1） in, for The inverse matrix of Indicates the target position of the calibration plate in the end-of-arm coordinate system. is a known quantity; Represents the position and posture of the camera in the coordinate system of the end of the robot arm. is a known quantity; Indicates the position and posture of the calibration plate in the camera coordinate system; Indicates the initial position of the end of the robot arm in the coordinate system of the robot arm base; According to the target position of the end of the manipulator in the manipulator base coordinate system The end of the robotic arm without the surgical navigation locator installed is moved so that the central theoretical position of the current surgical navigation locator is at the coordinate position p1 on the calibration plate.

3. The method for calibrating the center position of a surgical navigation locator according to claim 1, characterized in that: The step of determining the coordinate position p2 of the intersection of the robot arm end axis and the calibration plate on the calibration plate comprises: The monocular camera is used to identify the corner points on the calibration plate and obtain the attitude matrix of the calibration plate in the camera coordinate system before the end of the robot arm rotates. and the position matrix , merged into the following pose matrix: （2） in, - It represents the pose matrix parameters of the calibration plate in the camera coordinate system before the end of the manipulator rotates, which is calculated by the monocular camera recognizing the corner points on the calibration plate.

4. The method for calibrating the center position of a surgical navigation locator according to claim 3, characterized in that: The step of determining the coordinate position p2 of the intersection of the robot arm end axis and the calibration plate on the calibration plate at this time also includes: The monocular camera is used to identify the corner points on the calibration plate, and the posture matrix of the calibration plate in the camera coordinate system is obtained after the end of the robotic arm rotates an angle. and the position matrix , merged into the following pose matrix: （3） in, - It represents the pose matrix parameters of the calibration plate in the camera coordinate system after the end of the robotic arm rotates an angle, which is calculated by the monocular camera recognizing the corner points on the calibration plate.

5. The method for calibrating the center position of a surgical navigation locator according to claim 4, characterized in that: The step of determining the coordinate position p2 of the intersection of the robot arm end axis and the calibration plate on the calibration plate at this time also includes: According to the posture matrix , position matrix , attitude matrix , position matrix and the position matrix of the coordinate position p2 = , calculate the projection coordinates of the coordinate position p2 of the end of the robot before rotation in the camera image: （4） in , is the projection coordinate of the coordinate position p2 before the end of the robot arm rotates in the camera image, is the depth of the coordinate position p2 in the camera image before the end of the robot arm rotates.

6. The method for calibrating the center position of a surgical navigation locator according to claim 5, characterized in that: The step of determining the coordinate position p2 of the intersection of the robot arm end axis and the calibration plate on the calibration plate at this time also includes: According to the posture matrix , position matrix , attitude matrix , position matrix and the position matrix of the coordinate position p2 = , calculate the projection coordinates of the coordinate position p2 of the end of the robot after rotation in the camera image: （5） in , is the projection coordinate of the coordinate position p2 of the end of the robot after rotation in the camera image, It is the depth of the coordinate position p2 of the end of the robot arm before and after rotation in the camera image.

7. The method for calibrating the center position of a surgical navigation locator according to claim 6, characterized in that: The step of determining the coordinate position p2 of the intersection of the robot arm end axis and the calibration plate on the calibration plate at this time also includes: According to the above formulas (4) and (5), we can get: （6） in: is the horizontal coordinate of the coordinate position p2, is the ordinate of the coordinate position p2, ， ， ， ， ， ， ， ， ， ， ， ， Solve the above equation (6) to obtain the coordinate value (x, y) of the coordinate position p2.

8. The method for calibrating the center position of a surgical navigation locator according to claim 1, characterized in that: The step of moving the end of the mechanical arm to move the central theoretical position of the surgical navigation locator from the coordinate position p1 to the coordinate position p2 includes: The end of the robotic arm is moved a predetermined distance in a direction opposite to the direction in which the surgical navigation locator is located on the axis of the end of the robotic arm, wherein the predetermined distance is a vertical distance from the center of the surgical navigation locator to the axis of the end of the robotic arm.

9. The method for calibrating the center position of a surgical navigation locator according to claim 7, characterized in that: The step of converting the coordinate position p2 into the coordinate position p3 in the camera image comprises: After obtaining the coordinate value of the coordinate position p2, the corner points on the calibration plate are identified by the monocular camera to obtain the attitude matrix R and position matrix t of the calibration plate in the camera coordinate system; The coordinate value (x, y) of the coordinate position p2 is converted to the camera coordinate system according to the following formula: in is the coordinate of the coordinate position p2 in the camera coordinate system.

10. The method for calibrating the center position of a surgical navigation locator according to claim 9, characterized in that: The step of converting the coordinate position p2 into the coordinate position p3 in the camera image comprises: right Perform normalization to obtain normalized coordinates ; Assume the camera intrinsic parameter matrix is: in, and represents the focal length on the x-axis and y-axis, and represents the origin coordinates of the image coordinate system, , and The quantity is unknown; The normalized coordinates are calculated as follows: Convert to the pixel coordinate system of the camera image: According to the above calculation and , get the pixel coordinates of the projection of the theoretical center position of the surgical navigation locator in the camera image .

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