A high-precision treatment head automatic centering method

Abstract

The application discloses a high-precision treatment head automatic centering method, comprising the following steps: 1, camera system calibration of a camera; 2, a camera Cam1 acquires the texture of a third identification ring, determines the position of an identification disc, and plans a preliminary positioning track of a treatment head; 3, a mechanical arm moves, and the treatment head moves to a prepared position for alignment, thereby realizing preliminary centering of the treatment head; 4, a camera Cam2 and a camera Cam3 acquire the texture of a first identification ring and the third identification ring on the identification disc, determine the relative position of the treatment head and the identification disc, and plan a precise positioning track of the treatment head; and 5, a processor controls the movement of the mechanical arm, so that the treatment head is precisely centered with a light limiting cylinder. The application realizes full-automatic high-precision alignment of the treatment head and the light limiting cylinder by using two sets of identification members and two sets of cameras to guide the movement of the mechanical arm.

Description

Technical Field

[0001] This invention belongs to the field of radiotherapy equipment treatment head alignment technology, specifically relating to a high-precision automatic alignment method for treatment heads. Background Technology

[0002] Radiotherapy refers to local treatment using radiation to eliminate and eradicate primary and metastatic tumors. Radiotherapy, along with surgery and chemotherapy, constitutes the three basic treatment methods for tumors. However, radiotherapy has advantages such as wide applicability, definite efficacy, simple procedure, few side effects, and low requirements on the patient's own condition. About two-thirds of patients need radiotherapy during cancer treatment, making it one of the main treatment methods.

[0003] Intraoperative radiotherapy (IRT) is a high-dose radiation therapy administered under direct vision to visible tumors, tumor beds, or sites prone to recurrence and metastasis during surgery. Currently, in clinical practice, the movement of existing radiotherapy equipment into and out of the operating room, and adjustments to the patient's lesion site, are often hampered by limitations in the adjustment range and the need for manual adjustments. These adjustments are often not made in a single, efficient manner, requiring multiple adjustments over a considerable period, thus extending the overall surgical time and increasing the risk of infection for the patient. Therefore, there is a lack of a high-precision automatic alignment method for the treatment head, enabling highly accurate alignment of the fully automated treatment head with the light limiter. Summary of the Invention

[0004] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a high-precision automatic alignment method for a treatment head. Camera Cam1 acquires the texture of the third marker ring to determine the position of the marker disk. The processor plans the initial positioning trajectory of the treatment head and controls the movement of the robotic arm to achieve initial alignment of the treatment head. Cameras Cam2 and Cam3 acquire the textures of the first and third marker rings on the marker disk to determine the relative position of the treatment head and the marker disk. The processor plans the precise positioning trajectory of the treatment head and controls the movement of the robotic arm to achieve precise alignment of the treatment head with the light limiter. This fully automatic, high-precision alignment of the treatment head and the light limiter is easy to promote and use.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a high-precision automatic centering method for a treatment head, wherein the treatment head is mounted on a radiotherapy device, and the radiotherapy device includes...

[0006] Base: Used for support and fixation during the movement of the entire device and during treatment;

[0007] Fixed frame: Set on the base and fix the robotic arm;

[0008] Robotic arm: used to fix the treatment head and drive its movement;

[0009] Treatment head: Used for radiation therapy;

[0010] Beam limiting device: including a beam limiting tube and a marker plate installed on top of the beam limiting tube, which is used to align the patient's lesion area for collimation, dose distribution control and protection;

[0011] Image-guided alignment device: includes a processor, two sets of markers and two sets of cameras. One set of markers includes a first marker ring on the upper surface of the marker disc, a second marker ring on the edge of the upper surface of the marker disc, and a third marker ring on the outer surface of the marker disc. One set of cameras includes a first set of cameras mounted on a fixed frame. The other set of markers includes a treatment head marker on the side of the treatment head housing facing the fixed frame. The other set of cameras includes a second set of cameras mounted on the beam tube exit end face. The first set of cameras includes camera Cam1, and the second set of cameras includes camera Cam2 and camera Cam3.

[0012] There are three treatment head markers. The three treatment head markers are not in a straight line and are all spherical markers. The textures and colors of the three treatment head markers are all different.

[0013] The optical axis of camera Cam2 is parallel to the axis of the treatment head, while the optical axis of camera Cam3 is at an angle of 15° to 20° to the axis of the treatment head.

[0014] The method is characterized by comprising the following steps:

[0015] Step 1: Camera system calibration for cameras Cam1, Cam2, and Cam3;

[0016] Step 2: Camera Cam1 acquires the texture of the third marker ring, determines the position of the marker disc, and the processor plans the initial positioning motion trajectory of the treatment head.

[0017] Step 3: The processor controls the movement of the robotic arm to move the treatment head to the alignment preparation position, and then uses the field of view of cameras Cam2 and Cam3 to lock the position of the marker plate to achieve the initial alignment of the treatment head.

[0018] Step 4: Cameras Cam2 and Cam3 acquire the textures of the first and third marker rings on the marker disc, determine the relative position of the treatment head and the marker disc, and the processor plans the precise positioning motion trajectory of the treatment head.

[0019] Step 5: The processor controls the movement of the robotic arm to precisely align the treatment head with the light limiter.

[0020] The above-mentioned high-precision automatic centering method for a treatment head is characterized in that: in step two, the process of camera Cam1 acquiring the texture of the third marker ring and determining the position of the marker disk is as follows:

[0021] Step 201: Camera Cam1 continuously captures images of the third identification ring at a fixed frame rate;

[0022] Step 202: Within the field of view of camera Cam1, the processor identifies the arc-shaped line segment texture of the third identification ring;

[0023] Step 203: The processor fits an ellipse based on the arc-shaped line segment from step 202;

[0024] Step 204: Determine the major and minor axes of the ellipse;

[0025] Step 205: Determine the distance from the marker disc to the camera Cam1 based on the length of the major axis;

[0026] The position where the major and minor axes intersect in steps 206 and 203 is the center position of the marker disk. Based on the result of step 204, the coordinates of the center position of the marker disk relative to camera Cam1 are determined proportionally.

[0027] Step 207: Determine the orientation of the marker disk by the direction of the minor axis, the ratio of the major and minor axes, and the texture color inside the arc-shaped line segment.

[0028] The above-mentioned high-precision automatic alignment method for a treatment head is characterized in that: in step four, cameras Cam2 and Cam3 acquire the textures of the first and third marker rings on the marker disk, and the process of determining the relative position of the treatment head and the marker disk is as follows:

[0029] Step 401: Cameras Cam2 and Cam3 continuously acquire images of the first and third marker rings at a fixed frame rate;

[0030] Step 402: The processor processes the data from cameras Cam2 and Cam3 in a loop until the deviation of the pose of the treatment head from the target value is less than the tolerance value.

[0031] The above-mentioned high-precision automatic centering method for a treatment head is characterized in that: step 402 is as follows:

[0032] Step 4021: Calculate the angle of the marker disk relative to the camera Cam3 based on the data from the camera Cam3, and adjust the posture of the treatment head according to the angle deviation so that the beam axis of the treatment head is parallel to the normal vector of the upper plane of the marker disk.

[0033] Step 4022: Calculate the distance between the center of the marking plate and the lower end of the treatment head based on the data from camera Cam2, and adjust the position of the treatment head according to the distance deviation;

[0034] Step 4023: Calculate the coordinates of the center of the marker plate relative to the beam axis of the treatment head based on the camera Cam2 data, and adjust the position of the treatment head according to the coordinate deviation so that the beam axis of the treatment head overlaps with the central axis of the marker plate.

[0035] The above-mentioned high-precision automatic centering method for a treatment head is characterized in that: the process of step 4021 is as follows:

[0036] First, the processor identifies the ring-shaped texture on the surface of the disk in the image, which forms an elliptical ring in the image;

[0037] Then, calculate the ratio of the major axis to the minor axis of the outer ellipse of the elliptical ring, the direction of the minor axis, calculate the ratio of the first marking ring to the third marking ring, compare it with the calibrated data, and calculate the angular deviation of the marking disk relative to the camera Cam3.

[0038] The above-mentioned high-precision automatic centering method for a treatment head is characterized in that: the process of step 4022 is as follows:

[0039] First, the processor identifies the ring-shaped texture on the surface of the disk in the image, which forms an elliptical ring in the image;

[0040] Then, the major axis of the outer ellipse of the elliptical ring is calculated and compared with the calibrated data to calculate the distance deviation of the marker disk relative to the camera Cam2.

[0041] The above-mentioned high-precision automatic centering method for a treatment head is characterized in that: the process of step 4023 is as follows:

[0042] First, the processor identifies the ring-shaped texture on the surface of the disk in the image, which forms an elliptical ring in the image;

[0043] Then, the foci of the major and minor axes of the outer ellipse are calculated and compared with the calibrated data to calculate the deviation of the coordinates of the center of the labeling disc relative to the axis of the treatment head beam.

[0044] The beneficial effects of this invention are as follows: Camera Cam1 acquires the texture of the third marker ring to determine the position of the marker disk; the processor plans the initial positioning motion trajectory of the treatment head; the processor controls the movement of the robotic arm to achieve the initial centering of the treatment head; Cameras Cam2 and Cam3 acquire the textures of the first and third marker rings on the marker disk to determine the relative position of the treatment head and the marker disk; the processor plans the precise positioning motion trajectory of the treatment head; and controls the movement of the robotic arm to achieve precise centering of the treatment head and the light limiter, thus achieving fully automatic and high-precision alignment of the treatment head and the light limiter, which is convenient for widespread use.

[0045] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the radiotherapy device of the present invention.

[0047] Figure 2 This is a schematic diagram showing the positional relationship of the cameras Cam1, Cam2, and Cam3 of the present invention.

[0048] Figure 3 This is a schematic diagram showing the positional relationship between the cameras Cam2 and Cam3 of the present invention.

[0049] Figure 4 This is a schematic diagram of the beam-limiting device of the present invention.

[0050] Figure 5 This is a flowchart of the method of the present invention.

[0051] Explanation of reference numerals in the attached figures:

[0052] 100—Base; 110—Mount; 111—First set of cameras;

[0053] 120—Robotic arm; 130—Treatment head; 131—Treatment head marker;

[0054] 132—Treatment head outer shell; 133—Beam tube; 134—Second set of cameras;

[0055] 140—Beam limiting device; 141—First marking ring; 142—Second marking ring;

[0056] 143—Third identification ring; 144—Light limiting tube; 150—Beam limiting device positioning clip;

[0057] 160 — Treatment bed; 170 — Patient. Detailed Implementation

[0058] like Figures 1 to 5 As shown, this invention provides a high-precision automatic alignment method for a treatment head, wherein the treatment head is mounted on a radiotherapy device, and the radiotherapy device includes...

[0059] Base 100: Used for support and fixation during the movement of the entire device and during treatment;

[0060] Fixed frame 110: Set on the base 100 and fix the robotic arm 120;

[0061] Robotic arm 120: Used to fix the treatment head and drive its movement;

[0062] Treatment Head 130: Used for radiotherapy radiation;

[0063] Beam limiting device 140: includes a beam limiting tube 144 and a marker plate installed on top of the beam limiting tube 144, which is aligned with the lesion area of ​​the patient 170 for collimation of radiation, control of dose distribution and protection.

[0064] Image guidance alignment device: includes a processor, two sets of markers and two sets of cameras. One set of markers includes a first marker ring 141 disposed on the upper surface of the marker disc, a second marker ring 142 disposed on the edge of the upper surface of the marker disc, and a third marker ring 143 disposed on the outer surface of the marker disc. One set of cameras includes a first set of cameras 111 disposed on the fixed frame 110. The other set of markers includes a treatment head marker 131 disposed on the side of the treatment head housing 132 facing the fixed frame 110. The other set of cameras includes a second set of cameras 134 disposed on the exit end face of the beam tube 133. The first set of cameras 111 includes camera Cam1, and the second set of cameras 134 includes camera Cam2 and camera Cam3.

[0065] There are three treatment head markers 131. The three treatment head markers 131 are not in a straight line and are all spherical markers. The textures and colors of the three treatment head markers 131 are all different.

[0066] The optical axis of camera Cam2 is parallel to the axis of treatment head 130, and the optical axis of camera Cam3 is at an angle of 15° to 20° to the axis of treatment head 130.

[0067] It should be noted that the method of obtaining the relative tilt angle by identifying the major and minor axes of the second identification ring on the image actually approximates the slope of each point on the cosine curve in terms of accuracy. When the optical axis of the camera Cam3 is parallel to the axis of the treatment head 130, the corresponding slope is 0. To avoid this situation, Cam3 is installed at an angle to ensure the accuracy of the system in recognizing the relative posture of the positioning plate.

[0068] The method includes the following steps:

[0069] Step 1: Camera system calibration for cameras Cam1, Cam2, and Cam3;

[0070] Step 2: Camera Cam1 acquires the texture of the third marker ring 143, determines the position of the marker disc, and the processor plans the initial positioning motion trajectory of the treatment head 130.

[0071] Step 3: The processor controls the movement of the robotic arm 120 to move the treatment head 130 to the alignment preparation position. Then, the field of view of cameras Cam2 and Cam3 is used to lock the position of the marker plate to achieve the initial alignment of the treatment head 130.

[0072] Step 4: Cameras Cam2 and Cam3 acquire the textures of the first marker ring 141 and the third marker ring 143 on the marker disk, determine the relative position of the treatment head 130 and the marker disk, and the processor plans the precise positioning motion trajectory of the treatment head 130.

[0073] Step 5: The processor controls the movement of the robotic arm 120 to precisely align the treatment head 130 with the light-limiting tube 144.

[0074] It should be noted that during the calibration of the Cam1 camera, after manual positioning using an external positioning marker to ensure the system meets accuracy requirements, the current image is recorded and the corresponding parameter values ​​are calculated. Considering the linear relationship between distance and object size, at least two sets of data at different distances are recorded. At the same time, considering the need to calculate the offset for rotation angle, it is necessary to perform calibration at at least one distance with the marker disk tilted at 0° ("the marker disk is at a 90° angle with the horizontal axis", i.e., the light limiter is in the vertical direction).

[0075] When calibrating Cam2 and Cam3, after manual positioning using an external positioning marker device to ensure the system meets accuracy requirements, the current image is recorded and the corresponding parameter values ​​are calculated. Considering the linear relationship between distance and object size, at least two sets of data at different distances are recorded (Cam2 calibration); at the same time, considering that the rotation angle needs to be calculated for offset, it is necessary to perform correction at at least one distance with the relative tilt angle of the marker disk at 0° (the beam axis is parallel to the normal vector of the upper plane of the marker disk) (Cam3 calibration).

[0076] In this embodiment, in step two, the process of camera Cam1 acquiring the texture of the third marker ring 143 and determining the position of the marker disk is as follows:

[0077] Step 201: Camera Cam1 continuously captures images of the third identification ring 143 at a fixed frame rate;

[0078] Step 202: Within the field of view of camera Cam1, the processor identifies the arc-shaped line segment texture of the third identification ring 143;

[0079] Step 203: The processor fits an ellipse based on the arc-shaped line segment from step 202;

[0080] Step 204: Determine the major and minor axes of the ellipse;

[0081] Step 205: Determine the distance from the marker disc to the camera Cam1 based on the length of the major axis;

[0082] The position where the major and minor axes intersect in steps 206 and 203 is the center position of the marker disk. Based on the result of step 204, the coordinates of the center position of the marker disk relative to camera Cam1 are determined proportionally.

[0083] Step 207: Determine the orientation of the marker disk by the direction of the minor axis, the ratio of the major and minor axes, and the texture color inside the arc-shaped line segment.

[0084] In this embodiment, in step four, the process of cameras Cam2 and Cam3 acquiring the textures of the first marker ring 141 and the third marker ring 143 on the marker disk and determining the relative position of the treatment head 130 and the marker disk is as follows:

[0085] Step 401: Cameras Cam2 and Cam3 continuously acquire images of the first identifier ring 141 and the third identifier ring 143 at a fixed frame rate;

[0086] Step 402: The processor processes the data from cameras Cam2 and Cam3 in a loop until the deviation of the pose of the treatment head 130 from the target value is less than the tolerance value.

[0087] In this embodiment, step 402 is as follows:

[0088] Step 4021: Calculate the angle of the marker disk relative to the camera Cam3 based on the data from the camera Cam3, and adjust the posture of the treatment head according to the angle deviation so that the beam axis of the treatment head is parallel to the normal vector of the upper plane of the marker disk.

[0089] Step 4022: Calculate the distance between the center of the marking plate and the lower end of the treatment head based on the data from camera Cam2, and adjust the position of the treatment head according to the distance deviation;

[0090] Step 4023: Calculate the coordinates of the center of the marker plate relative to the beam axis of the treatment head based on the camera Cam2 data, and adjust the position of the treatment head according to the coordinate deviation so that the beam axis of the treatment head overlaps with the central axis of the marker plate.

[0091] In this embodiment, step 4021 is as follows:

[0092] First, the processor identifies the ring-shaped texture on the surface of the disk in the image, which forms an elliptical ring in the image;

[0093] Then, calculate the ratio of the major axis to the minor axis of the outer ellipse of the elliptical ring, the direction of the minor axis, calculate the ratio of the first marking ring to the third marking ring, compare it with the calibrated data, and calculate the angular deviation of the marking disk relative to the camera Cam3.

[0094] In this embodiment, step 4022 is as follows:

[0095] First, the processor identifies the ring-shaped texture on the surface of the disk in the image, which forms an elliptical ring in the image;

[0096] Then, the major axis of the outer ellipse of the elliptical ring is calculated and compared with the calibrated data to calculate the distance deviation of the marker disk relative to the camera Cam2.

[0097] In this embodiment, step 4023 is as follows:

[0098] First, the processor identifies the ring-shaped texture on the surface of the disk in the image, which forms an elliptical ring in the image;

[0099] Then, the foci of the major and minor axes of the outer ellipse are calculated and compared with the calibrated data to calculate the deviation of the coordinates of the center of the labeling disc relative to the axis of the treatment head beam.

[0100] In this embodiment, the first identification ring 141, the second identification ring 142, and the third identification ring 143 are all different colors.

[0101] In this embodiment, the limiting device 140 is fixed by the limiting device positioning clip 150, and the other end of the limiting device positioning clip 150 is fixed on the treatment bed 160.

[0102] It should be noted that the process by which the camera acquires the circular texture on the marking disc and calculates the position and orientation of the light-limiting tube is based on the following principle: For a camera with fixed parameters, the distance of the object from the camera is directly proportional to the size of its projection on the image. For a circle, different angles result in an ellipse projected onto the image, and the angle (relative to the axis of the treatment head) is cos... -1 (S / L), where S is the minor axis length and L is the major axis length. The tilt direction is obtained based on the direction of S. Since the optical axis of the Cam3 camera is at an angle of 15° to 20° to the axis of the treatment head, the calculated angle needs to be offset to obtain the actual angle. The direction of the angle offset can be obtained based on the different contents of the third marking ring on the light limiter shown in the image.

[0103] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Any simple modifications, alterations, or equivalent structural changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for automatic alignment of a high-precision treatment head, wherein the treatment head is mounted on a radiotherapy device, the radiotherapy device comprising... Base (100): Used for support and fixation during the movement of the entire device and during treatment; Fixed frame (110): Set on the base (100) and fixed to the robotic arm (120); Robotic arm (120): used to fix the treatment head and drive the movement of the treatment head; Treatment head (130): Used for radiotherapy radiation; Beam limiting device (140): includes a beam limiting tube (144) and a marker plate installed on top of the beam limiting tube (144), which is aligned with the lesion area of ​​the patient (170) for collimation of radiation, control of dose distribution and protection; Image guidance alignment device: includes a processor, two sets of markers and two sets of cameras. One set of markers includes a first marker ring (141) set on the upper surface of the marker disc, a second marker ring (142) set on the edge of the upper surface of the marker disc and a third marker ring (143) set on the outer surface of the marker disc. One set of cameras includes a first set of cameras (111) set on the fixed frame (110). The other set of markers includes a treatment head marker (131) set on the side of the treatment head housing (132) facing the fixed frame (110). The other set of cameras includes a second set of cameras (134) set on the exit end face of the beam tube (133). The first set of cameras (111) includes camera Cam1, and the second set of cameras (134) includes camera Cam2 and camera Cam3. There are three treatment head markers (131). The three treatment head markers (131) are not on a straight line and are all spherical markers. The textures and colors of the three treatment head markers (131) are all different. The optical axis of camera Cam2 is parallel to the axis of treatment head (130), and the optical axis of camera Cam3 is at an angle of 15° to 20° to the axis of treatment head (130). The method is characterized by comprising the following steps: Step 1: Camera system calibration for cameras Cam1, Cam2, and Cam3; Step 2: Camera Cam1 acquires the texture of the third marker ring (143), determines the position of the marker disc, and the processor plans the initial positioning motion trajectory of the treatment head (130). Step 3: The processor controls the movement of the robotic arm (120) to move the treatment head (130) to the alignment preparation position. Then, the field of view of the cameras Cam2 and Cam3 is used to lock the position of the marker plate to achieve the initial alignment of the treatment head (130). Step 4: Cameras Cam2 and Cam3 acquire the textures of the first and third marker rings (141 and 143) on the marker disk, determine the relative position of the treatment head (130) and the marker disk, and the processor plans the precise positioning motion trajectory of the treatment head (130). Step 5: The processor controls the movement of the robotic arm (120) to precisely align the treatment head (130) with the light limiter (144).

2. The high-precision automatic centering method for a treatment head according to claim 1, characterized in that: In step two, the process of camera Cam1 acquiring the texture of the third marker ring (143) and determining the position of the marker disk is as follows: Step 201: Camera Cam1 continuously captures images of the third identification ring (143) at a fixed frame rate; Step 202: Within the field of view of camera Cam1, the processor identifies the arc-shaped line segment texture of the third identification ring (143); Step 203: The processor fits an ellipse based on the arc-shaped line segment from step 202; Step 204: Determine the major and minor axes of the ellipse; Step 205: Determine the distance from the marker disc to the camera Cam1 based on the length of the major axis; The position where the major and minor axes intersect in steps 206 and 203 is the center position of the marker disk. Based on the result of step 204, the coordinates of the center position of the marker disk relative to camera Cam1 are determined proportionally. Step 207: Determine the orientation of the marker disk by the direction of the minor axis, the ratio of the major and minor axes, and the texture color inside the arc-shaped line segment.

3. The high-precision automatic centering method for a treatment head according to claim 2, characterized in that: In step four, cameras Cam2 and Cam3 acquire the textures of the first marker ring (141) and the third marker ring (143) on the marker disk, and the process of determining the relative position of the treatment head (130) and the marker disk is as follows: Step 401: Cameras Cam2 and Cam3 continuously acquire images of the first identifier ring (141) and the third identifier ring (143) at a fixed frame rate; Step 402: The processor processes the data from cameras Cam2 and Cam3 in a loop until the deviation of the pose of the treatment head (130) from the target value is less than the tolerance value.

4. The high-precision automatic centering method for a treatment head according to claim 3, characterized in that: The process of step 402 is as follows: Step 4021: Calculate the angle of the marker disk relative to the camera Cam3 based on the data from the camera Cam3, and adjust the posture of the treatment head according to the angle deviation so that the beam axis of the treatment head is parallel to the normal vector of the upper plane of the marker disk. Step 4022: Calculate the distance between the center of the marking plate and the lower end of the treatment head based on the data from camera Cam2, and adjust the position of the treatment head according to the distance deviation; Step 4023: Calculate the coordinates of the center of the marker plate relative to the beam axis of the treatment head based on the camera Cam2 data, and adjust the position of the treatment head according to the coordinate deviation so that the beam axis of the treatment head overlaps with the central axis of the marker plate.

5. A high-precision automatic centering method for a treatment head according to claim 4, characterized in that: The process of step 4021 is as follows: First, the processor identifies the ring-shaped texture on the surface of the disk in the image, which forms an elliptical ring in the image; Then, calculate the ratio of the major axis to the minor axis of the outer ellipse of the elliptical ring, the direction of the minor axis, calculate the ratio of the first marking ring to the third marking ring, compare it with the calibrated data, and calculate the angular deviation of the marking disk relative to the camera Cam3.

6. A high-precision automatic centering method for a treatment head according to claim 4, characterized in that: The process of step 4022 is as follows: First, the processor identifies the ring-shaped texture on the surface of the disk in the image, which forms an elliptical ring in the image; Then, the major axis of the outer ellipse of the elliptical ring is calculated and compared with the calibrated data to calculate the distance deviation of the marker disk relative to the camera Cam2.

7. A high-precision automatic centering method for a treatment head according to claim 4, characterized in that: The process of step 4023 is as follows: First, the processor identifies the ring-shaped texture on the surface of the disk in the image, which forms an elliptical ring in the image; Then, the foci of the major and minor axes of the outer ellipse are calculated and compared with the calibrated data to calculate the deviation of the coordinates of the center of the labeling disc relative to the axis of the treatment head beam.

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