A Method for Calibrating the Central Position of a Surgical Navigation Locator

Abstract

The present invention discloses a method for calibrating the central position of a surgical navigation locator, which relates to the field of computer-aided medical technology. The method includes: 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 theoretical central position of the surgical navigation locator and the end of the robotic arm, so that the current theoretical central position of the surgical navigation locator is at the coordinate position p1 on the calibration plate, and determining the coordinate position p2 on the calibration plate of the intersection point of the axis of the end of the robotic arm and the calibration plate at this time; moving the end of the robotic arm to move the theoretical central position of the surgical navigation locator from the coordinate position p1 to the coordinate position p2; converting the coordinate position p2 into the coordinate position p3 in the camera image. The present invention efficiently, accurately and conveniently solves the problem of positioning the theoretical position during the monitoring of the deviation of the central point of the surgical navigation locator.

Description

Technical Field

[0001] The present invention relates to the field of computer-aided medical technology, and particularly relates to a method for calibrating the central position of a surgical navigation locator. Background Art

[0002] The existing surgical navigation locator is installed at the end of a robotic arm and is used to hold a surgical instrument through the center point and perform positioning and navigation during surgery. When the surgical navigation locator is stressed, lateral offsets in the X and Z directions will occur, with the offset range within 0 - 5 mm. Such offsets will affect the intraoperative positioning accuracy. To monitor the position and movement of the surgical navigation locator, it is necessary to calculate the central position error of the surgical navigation locator and also obtain the theoretical position of the center of the surgical navigation locator. However, 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 deficiencies in the prior art, the present invention provides a method for calibrating the central position of a surgical navigation locator. In this method, a monocular camera is fixed to the end of the robotic arm through a tooling, and in combination with the camera image and a calibration board, the theoretical position of the center point of the surgical navigation locator in the camera is calibrated. This method efficiently, accurately, and conveniently solves the problem of positioning the theoretical position during the monitoring of the offset of the center point of the surgical navigation locator.

[0004] The present invention provides a method for calibrating the central position of a surgical navigation locator, including the following steps: 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 board is equal to the vertical distance between the theoretical central position of the surgical navigation locator and the end of the robotic arm, so that the current theoretical central position of the surgical navigation locator is at the coordinate position p1 on the calibration board, and determine the coordinate position p2 on the calibration board of the intersection point of the axis of the end of the robotic arm and the calibration board at this time; Move the end of the robotic arm so that the theoretical central position of the surgical navigation locator moves from the coordinate position p1 to the coordinate position p2; Convert the coordinate position p2 into the coordinate position p3 in the camera image.

[0005] The method for calibrating the central position of the surgical navigation locator provided by the present invention overcomes the defects of inconvenience, low accuracy, and low efficiency caused by using sensors with large volume and low accuracy to calibrate the central position of the surgical navigation locator in the prior art. 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 during the monitoring of the offset of the center point of the surgical navigation locator. Brief Description of the Drawings

[0006] By reading the detailed description of the non-restrictive embodiments with reference to the following drawings, other features, objectives, and advantages of the present application will become more obvious:

[0007] Figure 1 is a schematic structural diagram of a surgical navigation positioning device provided by an embodiment of the present application;

[0008] Figure 2 is a schematic flowchart of a method for calibrating the central position of a surgical navigation locator provided by an embodiment of the present application;

[0009] Figure 3 is a schematic scenario diagram of a method for calibrating the central position of a surgical navigation locator provided by an embodiment of the present application. Detailed implementation manners

[0010] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0011] 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", "the", and "said" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0012] 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, these acquisition modules should not be limited to these terms. These terms are only used to distinguish the acquisition modules from each other.

[0013] Depending on the context, the word "if" as used herein may be interpreted as "when" or "while" or "in response to determining" or "in response to detecting". Similarly, depending on the context, the phrase "if determined" or "if detecting (stated condition or event)" may be interpreted as "when determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)".

[0014] It should be noted that the orientation terms such as "upper", "lower", "left", and "right" described in the embodiments of the present invention are described from the angles shown in the drawings and should not be construed 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 directly formed "on" or "under" another element, but also be indirectly formed "on" or "under" another element through an intermediate element.

[0015] The invention objective of the present application is to provide a method for calibrating the central 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 a calibration board, the theoretical position of the center point of the surgical navigation locator in the camera is calibrated. After accurately obtaining the theoretical position of the center point of the surgical navigation locator in the camera, subsequently, by comparing the actual position of the center point of the surgical navigation locator, the position deviation of the surgical navigation locator can be tracked and monitored.

[0016] Based on the similar working principle of the surgical navigation locator, the method for calibrating the central position of the surgical navigation locator proposed in the present application is applicable to all types of surgical navigation locators that hold surgical instruments through the clamping center point (abbreviated as the center point) of the surgical navigation locator. Exemplarily, the present application takes a double-ring locator as an example for detailed description.

[0017] See Figure 1 , the surgical navigation positioning device 100 includes: a robotic arm 101, a surgical navigation locator 102, a monocular camera 103, a first fixing device 104, and a second fixing device 105. The monocular camera 103 is installed at the end of the robotic arm 106 through the first fixing device 104, the surgical navigation locator 102 is installed at the end of the robotic arm 106 through the second fixing device 105. The axis in the length direction of the surgical navigation locator 102 is parallel to the axis of the end of the robotic arm. The second fixing device 105 is used to drive the surgical navigation locator 102 to move up and down in a direction perpendicular to the axis of the end of the robotic arm 106.

[0018] Optionally, the surgical navigation locator 102 is a double-ring locator, including a first circular part 1021, a second circular part, and a line segment part that can be imaged under a medical imaging device; wherein, the first circular part 1021 and the second circular part are coaxial, the diameter of the first circular part 1021 is smaller than the diameter of the second circular part, the line segment part extends along the radial direction of the first circular part 1021, and the center of the surgical navigation locator 102 is the center of the first circular part 1021 or the center of the second circular part.

[0019] Further, the first fixing device 104 is fixedly connected to a flange 107, and the flange 107 is fixed to the end of the robotic arm 106.

[0020] Further, the second fixing device 105 is an L-shaped lifting slide rail, and the L-shaped lifting slide rail is fixed to the flange 107.

[0021] There is a design dimension for the above double-ring locator. Due to factors such as machining errors and force deformation during use, there is a deviation between the actual position and the theoretical position of the clamping center of the double-ring locator. To monitor and calculate this deviation, it is necessary to first accurately calibrate its central theoretical position.

[0022] See Figure 2 , for the method of calibrating the central position of the surgical navigation locator provided by an embodiment of the present application, the theoretical central position of the double-ring locator is efficiently and accurately calibrated by a monocular camera and a calibration board, and the specific steps are as follows:

[0023] 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 board is equal to the vertical distance between the theoretical central position of the surgical navigation locator and the end of the robotic arm, so that the theoretical central position of the current surgical navigation locator is at the coordinate position p1 on the calibration board, and determine the coordinate position p2 of the intersection of the axis of the end of the robotic arm and the calibration board on the calibration board at this time.

[0024] See Figure 3 , for the method of this embodiment, the theoretical central position of the surgical navigation locator is accurately positioned when the surgical navigation locator is not installed. Assume that the clamping center of the double-ring locator is , the axis in the self-length direction of the double-ring locator is on a straight line parallel to the axis of the end of the robotic arm, and the theoretical distance between the two axes l is known. In addition, the height of the clamping center point from the end of the robotic arm h is known.

[0025] 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 board is equal to the vertical distance between the theoretical central 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 board in the camera.

[0026] The first stage: Move the robotic arm so that the height between the end of the robotic arm and the calibration board is the theoretical height h . In order to move the end of the robotic arm to this target position, it can be achieved by the following method:

[0027] Step S1011, identify the corner points on the calibration board through a monocular camera to obtain the pose of the calibration board in the camera coordinate system ;

[0028] Step S1012, calculate the initial pose of the end of the robotic arm in the robotic arm base coordinate system through the initial position of the end of the robotic arm and the position relationship between the end of the robotic arm and the robotic arm base ;

[0029] Step S1013, calculate the target pose of the end of the robotic arm in the robotic arm base coordinate system when the vertical distance between the end of the robotic arm and the calibration board is equal to the vertical distance between the theoretical central position of the double-ring locator and the end of the robotic arm according to the following formula :

[0030] (1)

[0031] Wherein, is the inverse matrix of indicating the target pose of the calibration board in the coordinate system of the end of the robotic arm, which is a known quantity; indicating the pose of the camera in the coordinate system of the end of the robotic arm, which is a known quantity; indicating the pose of the calibration board in the camera coordinate system; indicating the initial pose of the end of the robotic arm in the coordinate system of the robotic arm base;

[0032] According to the target pose of the end of the robotic arm in the coordinate system of the robotic arm base move the end of the robotic arm without the double-ring locator installed so that the theoretical position of the center of the current double-ring locator is at the coordinate position p1 on the calibration board.

[0033] Second stage: After the robotic arm to be moved arrives, then determine the coordinate position p2 on the calibration board of the intersection point of the axis of the end of the robotic arm and the calibration board at this time. Specifically, it can be found by rotating the end of the robotic arm. When the end of the robotic arm rotates, the projection position of the intersection point of the axis of the end of the robotic arm and the calibration board in the camera is stationary. Therefore, the stationary intersection point, that is, the coordinate position p2, can be found by rotating the robotic arm.

[0034] Specifically, it includes:

[0035] Step S1014, identify the corner points on the calibration board through a monocular camera to obtain the attitude matrix and the position matrix of the calibration board in the camera coordinate system before the end of the robotic arm rotates, and merge them into the following pose matrix:

[0036] (2)

[0037] Wherein, - represents the pose matrix parameters of the calibration board in the camera coordinate system before the end of the robotic arm rotates, calculated by identifying the corner points on the calibration board through a monocular camera;

[0038] Step S1015, identify the corner points on the calibration board through a monocular camera to obtain the attitude matrix and the position matrix of the calibration board in the camera coordinate system after the end of the robotic arm rotates by an angle, and merge them into the following pose matrix:

[0039] (3)

[0040] Among them, - represents the pose matrix parameters of the calibration board in the camera coordinate system after the end of the robotic arm rotates by an angle, calculated from the corner points recognized by the monocular camera on the calibration board;

[0041] Step S1016, according to the pose matrix , position matrix , pose matrix , position matrix and the position matrix of the coordinate position p2 = , calculate the projection coordinates of the coordinate position p2 at the end of the robotic arm before rotation in the camera image:

[0042] (4)

[0043] Where , are the projection coordinates of the coordinate position p2 at the end of the robotic arm before rotation in the camera image, is the depth of the coordinate position p2 at the end of the robotic arm before rotation in the camera image;

[0044] Step S1017, according to the pose matrix , position matrix , pose matrix , position matrix and the position matrix of the coordinate position p2 = , calculate the projection coordinates of the coordinate position p2 at the end of the robotic arm after rotation in the camera image:

[0045] (5)

[0046] Where , are the projection coordinates of the coordinate position p2 at the end of the robotic arm after rotation in the camera image, is the depth of the coordinate position p2 at the end of the robotic arm before and after rotation in the camera image;

[0047] Step S1018, according to the above formulas (4) and (5), it can be calculated that:

[0048] (6)

[0049] Where:

[0050] is the abscissa of the coordinate position p2,

[0051] is the ordinate of the coordinate position p2,

[0052] ,

[0053] ,

[0054] ,

[0055] ,

[0056] ,

[0057] ,

[0058] ,

[0059] ,

[0060] ,

[0061] ,

[0062] ,

[0063] ,

[0064] Solve the above formula (6) to obtain the coordinate values (x, y) of the coordinate position p2.

[0065] Step S102: Move the end of the robotic arm so that the theoretical center position of the surgical navigation locator moves from the coordinate position p1 to the coordinate position p2.

[0066] Specifically, after obtaining the coordinate position p2 in step S101, then start to find the theoretical position of the clamping center of the double-ring locator in the camera image. Since the clamping center point of the double-ring locator is at a l distance from the axis of the end of the robotic arm, and as Figure 3 shown, the direction of this center point is directly behind the end of the robotic arm. Therefore, after moving the end of the robotic arm forward by l distance, at this time the coordinate position coincides with the theoretical center position of the double-ring locator. In short, move the end of the robotic arm a predetermined distance in the opposite direction of the direction of the double-ring locator located on the axis of the end of the robotic arm, and the predetermined distance is the perpendicular distance from the center of the double-ring locator to the axis of the end of the robotic arm, so that the theoretical center position of the double-ring locator can move from the coordinate position p1 to the coordinate position p2.

[0067] Step S103: Convert the coordinate position p2 into the coordinate position p3 in the camera image.

[0068] Specifically, projecting the coordinate position onto the camera image can obtain the position of this point in the camera image, which is specifically implemented through the following steps:

[0069] Step S1031: After obtaining the coordinate values of the coordinate position p2, identify the corner points on the calibration board through a monocular camera to obtain the attitude matrix R and the position matrix t of the calibration board in the camera coordinate system;

[0070] Step S1032: Convert the coordinate values (x, y) of the coordinate position p2 into the camera coordinate system according to the following formula:

[0071]

[0072] where is the coordinate of the coordinate position p2 in the camera coordinate system;

[0073] Step S1033: Perform normalization processing on to obtain the normalized coordinate ;

[0074] Step S1034: Assume the camera internal parameter matrix is:

[0075]

[0076] where, and represent the focal lengths on the x-axis and y-axis, and represent the origin coordinates of the image coordinate system, , and are all known quantities;

[0077] Step S1035: Convert the normalized coordinate into the pixel coordinate system of the camera image according to the following formula:

[0078]

[0079] Step S1036: Calculate and according to the above formula to obtain the pixel coordinates of the projection of the center theoretical position of the double-ring locator in the camera image, that is, the coordinate position p3.

[0080] After calculating the pixel coordinates of the projection of the theoretical center position of the double-ring locator in the camera image (i.e., the coordinate position p3), the subsequent 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 this embodiment is described by taking the double-ring locator as an example, the method of this embodiment is not only applicable to the double-ring locator, but also applicable to other surgical navigation locators with a clamping center point, which will not be elaborated in this embodiment.

[0081] The method for calibrating the center position of the surgical navigation locator in this embodiment overcomes the defects of inconvenience, low accuracy and low efficiency caused by calibrating the center position of the surgical navigation locator by using a large-sized and low-precision sensor in the prior art. A monocular camera is selected as the monitoring device, and an innovative position calibration algorithm is used to realize the efficient, accurate and convenient calibration of the theoretical position during the monitoring of the center point offset of the surgical navigation locator.

[0082] The above description is only a preferred embodiment of the present invention. Those skilled in the art should understand that the disclosed scope in the present invention is not limited to the technical solutions formed by the specific combination of the above technical features, and should also 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 technical solutions formed by mutually replacing the above features with the technical features (but not limited to) having similar functions disclosed in the present invention.

Claims

1. A method for calibrating the center position of a surgical navigation locator, characterized in that: The surgical navigation positioning device comprises: a mechanical arm, a surgical navigation positioning device, a monocular camera, a first fixing device and a second fixing device, wherein the monocular camera is mounted on the end of the mechanical arm through the first fixing device, and the surgical navigation positioning device is mounted on the end of the mechanical arm through the second fixing device, wherein the axis of the surgical navigation positioning device in the length direction is parallel to the axis of the end of the mechanical arm, and the second fixing device is used to drive the surgical navigation positioning device to move up and down in a direction perpendicular to the axis of the end of the mechanical arm; The method comprises the following steps: 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 central theoretical position of the surgical navigation locator and the end of the manipulator arm, so that the current central theoretical position of the surgical navigation locator is at the coordinate position p1 on the calibration plate in the manipulator arm end coordinate system, and determine the coordinate position p2 of the intersection of the axis of the manipulator arm end and the calibration plate on the calibration plate in the manipulator arm end coordinate system; 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 monocular 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 monocular 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 monocular camera in the coordinate system of the end of the robotic arm, is a known quantity; Indicates the position and posture of the calibration plate in the monocular 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 monocular camera coordinate system before the end of the robot arm rotates. , merged into the following pose matrix: （2） in, - It represents the pose matrix parameters of the calibration plate in the monocular 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 monocular 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 monocular 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.

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 , and the position matrix of the coordinate position p2 = , calculate the projection coordinates of the coordinate position p2 of the end of the manipulator before rotation in the monocular camera image: （4） in , is the projection coordinate of the coordinate position p2 before the end of the robot arm rotates in the monocular camera image, is the depth of the coordinate position p2 before the end of the robot arm rotates in the monocular camera image.

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 , 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 monocular camera image: （5） in , is the projection coordinate of the coordinate position p2 of the end of the robot after rotation in the monocular camera image, It is the depth of the coordinate position p2 of the end of the robot arm before and after rotation in the monocular 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 monocular 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 posture matrix R and position matrix t of the calibration plate in the monocular camera coordinate system; The coordinate value (x, y) of the coordinate position p2 is converted to the monocular camera coordinate system according to the following formula: in is the coordinate of the coordinate position p2 in the monocular 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 monocular camera image comprises: right Perform normalization to obtain normalized coordinates ; Assume the intrinsic parameter matrix of the monocular camera 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 All are known quantities; The normalized coordinates are calculated as follows: Convert to the pixel coordinate system of the monocular camera image: According to the above calculation , get the pixel coordinates of the projection of the theoretical center position of the surgical navigation locator in the monocular camera image .

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