Face point cloud registration method and device by taking points in C-type region

Abstract

The face point cloud registration method and device taking points through the C-shaped area can train the collected data, realize position matching with a real patient, and realize accurate positioning of a surgical instrument in a surgical area. The method comprises the following steps: (1) starting an optical tracking device; (2) contacting a tracking tool tip with a tracking small ball to the patient's skin surface to achieve the purpose that all tracking points are actual positions on the patient's skin; (3) starting to collect point cloud data, and drawing a C-shaped line on the patient's head by holding the tracking tool; (4) judging whether the number of collected points reaches a specified number, if yes, executing step (5), otherwise executing step (3); (5) ending the collection and starting the matching, adopting a 4PCS four-point congruent set registration method to perform the matching, and saving a relative position relationship conversion matrix; and (6) ending.

Description

Technical Field

[0001] This invention relates to the field of medical image processing technology, and more particularly to a face point cloud registration method and a face point cloud registration device that uses C-type region sampling, mainly for use in the field of surgical navigation. Background Technology

[0002] Currently, most hospitals use endoscopes as surgical navigation tools in ENT or skull base surgery. The main function of endoscopes is to help doctors see the tissue structure of organs around the skull base, observe and magnify the location of lesions and perform surgery. Using endoscopes can minimize the area and size of surgery performed outside the body, reducing the need for anesthesia. It is a minimally invasive technique that is widely used in the medical industry.

[0003] Taking endoscopic-guided neurosurgery as an example, surgeons can treat pituitary adenomas located at the base of the skull without opening the skull, and perform minimally invasive surgeries within the nasal cavity. This breaks through traditional surgical taboos, allowing highly complex lesions to be treated without damaging local normal anatomical structures. However, using only an endoscope cannot observe the distribution of subcutaneous tissues such as blood vessels and optic nerves. In skull base surgery, surgeons are most concerned about accidentally touching these vital and irreversibly damaged tissues and organs during the procedure. To avoid this, a relatively new method is to use optical or electromagnetic tracking equipment to guide surgical instruments within the patient's body. The system tracks the patient's position in real time and uses computer vision technology to reconstruct the surgical site and surrounding area in three dimensions based on the patient's preoperative CT data. This allows important subcutaneous tissues and organs to be displayed completely and three-dimensionally on the screen. When the surgeon moves the surgical instruments, a three-dimensional visualization system displays the tip of the instrument and the subcutaneous tissue on the screen to assist the surgeon in performing the operation. Before the operation, it is necessary to match the patient's actual position with the three-dimensional reconstruction model of the patient in the three-dimensional virtual space. The accuracy of the matching is particularly important, as it reflects the actual positional relationship between the surgical instruments and important tissues and organs. Excessive matching error may endanger the patient's health or even life. Therefore, a reasonable and safe matching method is crucial. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a face point cloud registration method by taking points in a C-shaped region, which can train the collected data to achieve position matching with the real patient and achieve precise positioning of surgical instruments in the surgical area.

[0005] The technical solution of this invention is: a face point cloud registration method using C-shaped region sampling, which includes the following steps: (1) Turn on the optical tracking device; (2) The tip of the tracking tool with the tracking ball is brought into contact with the patient's skin surface so that the tracking points are all the actual locations on the patient's skin; (3) Start collecting point cloud data and draw a C-shape on the patient's head with a handheld tracking tool; (4) Determine whether the number of collection points has reached the specified number. If yes, proceed to step (5); otherwise, proceed to step (3). (5) End the collection and start the matching. Use the 4PCS four-point congruent set registration method to perform the matching and save the relative position relationship transformation matrix; (6) End.

[0006] This invention employs a 4PCS four-point identical set registration method for matching. Compared to traditional methods, this method does not require a large overlap between point clouds for successful matching, making it suitable for registration of two point cloud images with small overlap areas. Furthermore, this method can handle complex point cloud registration tasks. During actual point acquisition, to facilitate data collection, the position information of the tracked ball needs to be converted into the position of the tracking tool's tip (the tip of the tracking tool that contacts the patient's skin) based on the size of the tracking tool. Since the tracking tool is a rigid body, only a fixed rotation matrix is ​​needed to complete the conversion. Considering that in actual ENT or skull base surgery, procedures such as intubation and disinfection of the patient's nasal cavity may cause deformation, affecting the matching effect with the 3D model, a C-shaped point acquisition area is used to collect data points, primarily in the patient's forehead and periorbital areas. These areas are generally not processed in these surgeries and will not be affected by deformation. Therefore, this method can train the acquired data to achieve position matching with the real patient, enabling precise positioning of surgical instruments in the surgical area.

[0007] A face point cloud registration device based on C-type region sampling is also provided, which includes: The device module, configured to enable the optical tracking device; The tracking module is configured to bring the tip of a tracking tool with a tracking ball into contact with the patient's skin surface so that the tracking points are all the actual locations on the patient's skin. The collection module, configured to begin collecting point cloud data, uses a handheld tracking tool to draw a C-shape on the patient's head. The judgment module is configured to determine whether the number of collection points has reached a specified number. If so, the matching module is executed; otherwise, the collection module is executed. The matching module is configured to end collection and begin matching. It uses the 4PCS four-point congruent set registration method for matching and saves the relative position relationship transformation matrix. Attached Figure Description

[0008] Figure 1 This is a flowchart of the face point cloud registration method based on C-type region sampling according to the present invention. Detailed Implementation

[0009] like Figure 1 As shown, this face point cloud registration method using C-shaped region sampling includes the following steps: (1) Turn on the optical tracking device; (2) The tip of the tracking tool with the tracking ball is brought into contact with the patient's skin surface so that the tracking points are all the actual locations on the patient's skin; (3) Start collecting point cloud data and draw a C-shape on the patient's head with a handheld tracking tool; (4) Determine whether the number of collection points has reached the specified number. If yes, proceed to step (5); otherwise, proceed to step (3). (5) End the collection and start the matching. Use the 4PCS four-point congruent set registration method to perform the matching and save the relative position relationship transformation matrix; (6) End.

[0010] This invention employs a 4PCS four-point identical set registration method for matching. Compared to traditional methods, this method does not require a large overlap between point clouds for successful matching, making it suitable for registration of two point cloud images with small overlap areas. Furthermore, this method can handle complex point cloud registration tasks. During actual point acquisition, to facilitate data collection, the position information of the tracked ball needs to be converted into the position of the tracking tool's tip (the tip of the tracking tool that contacts the patient's skin) based on the size of the tracking tool. Since the tracking tool is a rigid body, only a fixed rotation matrix is ​​needed to complete the conversion. Considering that in actual ENT or skull base surgery, procedures such as intubation and disinfection of the patient's nasal cavity may cause deformation, affecting the matching effect with the 3D model, a C-shaped point acquisition area is used to collect data points, primarily in the patient's forehead and periorbital areas. These areas are generally not processed in these surgeries and will not be affected by deformation. Therefore, this method can train the acquired data to achieve position matching with the real patient, enabling precise positioning of surgical instruments in the surgical area.

[0011] Preferably, in step (1), the optical tracking device is a binocular vision tracking device. The device emits infrared light within a certain range and analyzes the intensity of the infrared light reflected back to the device's camera to identify the tracking object. The tracking tool is a probe with an optical tracking ball. The optical tracking ball is a ball coated with a special coating. The special coating has a very strong ability to reflect infrared light, so that the infrared light emitted by the optical tracking device is reflected back as much as possible, making it easier for the tracking device to identify the position of the ball to achieve the tracking purpose.

[0012] Preferably, in step (2), during the collection point, once the tip of the tracking tool leaves the skin surface, tracking and data collection are stopped and restarted.

[0013] Preferably, in step (3), the tip of the tracking tool moves repeatedly at a constant speed within the green area, and the tip covers every position within the area.

[0014] Preferably, in step (3), the C-type region is the patient's forehead region and the area around the eyes.

[0015] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium. When executed, the program includes the steps of the methods of the above embodiments. The storage medium can be ROM / RAM, magnetic disk, optical disk, memory card, etc. Therefore, corresponding to the method of the present invention, the present invention also includes a face point cloud registration device using C-type region sampling. This device is typically represented as functional modules corresponding to the steps of the method. The device includes: The device module, configured to enable the optical tracking device; The tracking module is configured to bring the tip of a tracking tool with a tracking ball into contact with the patient's skin surface so that the tracking points are all the actual locations on the patient's skin. The collection module, configured to begin collecting point cloud data, uses a handheld tracking tool to draw a C-shape on the patient's head. The judgment module is configured to determine whether the number of collection points has reached a specified number. If so, the matching module is executed; otherwise, the collection module is executed. The matching module is configured to end collection and begin matching. It uses the 4PCS four-point congruent set registration method for matching and saves the relative position relationship transformation matrix.

[0016] Preferably, in the device module, the device is a binocular vision tracking device. This device emits infrared light within a certain range and analyzes the intensity of the infrared light reflected back to the device's camera to identify the tracking object. The tracking tool is a probe with an optical tracking ball. The optical tracking ball is a ball coated with a special coating. The special coating has extremely strong infrared reflectivity, so that the infrared light emitted by the optical tracking device is reflected back as much as possible, making it easier for the tracking device to identify the position of the ball to achieve the tracking purpose.

[0017] Preferably, in the tracking module, during the collection point, once the tip of the tracking tool leaves the skin surface, tracking and data collection stop and restart.

[0018] Preferably, in the collection module, the tip of the tracking tool moves repeatedly at a constant speed within the green area, and the tip covers every position within the area.

[0019] Preferably, in the collection module, the C-shaped region is the patient's forehead region and the area around the eyes.

[0020] The present invention will now be described in more detail.

[0021] The present invention addresses the premise of using the aforementioned surgical navigation system, which requires the use of optical tracking equipment and related tools to collect the necessary data, and combines point cloud training model methods to train the collected data to achieve matching with the position of the real patient, thereby achieving precise positioning of surgical instruments in the surgical area.

[0022] The optical tracking equipment and related tools mainly consist of a binocular vision tracking device. This device can emit infrared light within a certain range and analyze the intensity of the infrared light reflected back to the device's camera to identify the tracking object. The tracking tool mainly consists of a probe with an optical tracking ball. The optical tracking ball is a small ball coated with a special coating. This special coating has extremely strong infrared reflectivity, allowing the infrared light emitted by the optical tracking device to be reflected back as much as possible, making it easier for the tracking device to identify the position of the ball to achieve the tracking purpose.

[0023] Point cloud matching methods work by first constructing local geometric features from point cloud data, and then relocalizing the point cloud data based on these features. 3D point cloud registration involves aligning the point cloud with the target model through transformations such as rotation and translation. This alignment process yields a 4x4 transformation matrix containing a 3x3 rotation matrix and a 3x1 translation vector. Commonly used point cloud registration methods include: Iterative Closest Point (ICP), Normal Distribution Transform (NDT) registration, feature invariance-based registration (ORB / FPFH / NARF), and their evolutionary methods.

[0024] This invention employs the 4PCS (4-point congruent sets) method for matching. Compared to the traditional methods mentioned above, this method does not require a large overlap between point clouds for successful matching. It is suitable for registration of two point cloud images with a small overlap area and can handle complex point cloud registration tasks. In the actual point acquisition process, to facilitate data collection, the tracked ball position information needs to be converted into the position of the tracking tool's tip (the tip of the tracking tool that contacts the patient's skin) based on the size of the tracking tool. Since the tracking tool is a rigid body, only a fixed rotation matrix is ​​needed to complete the conversion.

[0025] Considering that in actual ENT or skull base surgery, procedures such as intubation and disinfection of the patient's nasal cavity are required, which may cause deformation of the patient's nose and affect the matching effect with the 3D model, a "C"-shaped sampling area is used to collect data points. The main areas are the patient's forehead and periorbital area, which are generally not treated in the above-mentioned surgeries and will not be affected by deformation.

[0026] The present invention has the following beneficial effects: This registration method can quickly and accurately register real objects with corresponding three-dimensional models, and the high registration accuracy can assist doctors in performing some surgeries with strict distance accuracy requirements, reduce surgical risks, ensure surgical safety, and can also be used as a surgical training tool to quickly improve the surgical skills of doctors without surgical experience, establish the three-dimensional spatial effect around the patient's lesion, and further restore the real surgical scene.

[0027] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations 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 face point cloud registration method using C-type region sampling, characterized in that: It includes the following steps: (1) Turn on the optical tracking device; (2) The tip of the tracking tool with the tracking ball is brought into contact with the patient's skin surface so that the tracking points are all the actual locations on the patient's skin; (3) Start collecting point cloud data and draw a C-shape on the patient's head with a handheld tracking tool; (4) Determine whether the number of collection points has reached the specified number. If yes, proceed to step (5); otherwise, proceed to step (3). (5) End the collection and start the matching. Use the 4PCS four-point congruent set registration method to perform the matching and save the relative position relationship transformation matrix; (6) End; The C-type area refers to the patient's forehead and the area around the eyes.

2. The face point cloud registration method using C-type region sampling as described in claim 1, characterized in that: In step (1), the optical tracking device is a binocular vision tracking device. The device emits infrared light within a certain range and analyzes the intensity of the infrared light reflected back to the device's camera to identify the tracking object. The tracking tool is a probe with an optical tracking ball. The optical tracking ball is a ball coated with a special coating. The special coating has a very strong ability to reflect infrared light, so that the infrared light emitted by the optical tracking device is reflected back as much as possible, making it easier for the tracking device to identify the position of the ball to achieve the tracking purpose.

3. The face point cloud registration method using C-type region sampling as described in claim 2, characterized in that: In step (2), during the collection point, once the tip of the tracking tool leaves the skin surface, tracking and data collection stop and restart.

4. The face point cloud registration method using C-type region sampling as described in claim 3, characterized in that: In step (3), the tip of the tracking tool moves repeatedly at a constant speed within the C-shaped region, and the tip covers every position within the region.

5. A face point cloud registration device that uses C-type region sampling, characterized in that: It includes: The device module, configured to enable the optical tracking device; The tracking module is configured to bring the tip of a tracking tool with a tracking ball into contact with the patient's skin surface so that the tracking points are all the actual locations on the patient's skin. The collection module, configured to begin collecting point cloud data, uses a handheld tracking tool to draw a C-shape on the patient's head. The judgment module is configured to determine whether the number of collection points has reached a specified number. If so, the matching module is executed; otherwise, the collection module is executed. The matching module is configured to end collection and begin matching. It uses the 4PCS four-point congruent set registration method for matching and saves the relative position relationship transformation matrix. The C-type area refers to the patient's forehead and the area around the eyes.

6. The face point cloud registration device based on C-type region sampling according to claim 5, characterized in that: In the device module, the optical tracking device is a binocular vision tracking device. This device emits infrared light within a certain range and analyzes the intensity of the infrared light reflected back to the device's camera to identify the tracking object. The tracking tool is a probe with an optical tracking ball. The optical tracking ball is a small ball coated with a special coating. The special coating has extremely strong infrared light reflection capabilities, so that the infrared light emitted by the optical tracking device is reflected back as much as possible, making it easier for the tracking device to identify the position of the ball to achieve the tracking purpose.

7. The face point cloud registration device based on C-type region sampling according to claim 6, characterized in that: In the tracking module, during the data collection period, once the tip of the tracking tool leaves the skin surface, tracking and data collection stop and restart.

8. The face point cloud registration device based on C-type region sampling according to claim 7, characterized in that: In the collection module, the tip of the tracking tool moves repeatedly at a constant speed within the C-shaped region, and the tip covers every position within the region.

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