A method and system for automatic coordinate registration in surgical navigation

Abstract

The present application relates to surgical navigation automatic registration technical field, provide a kind of coordinate automatic registration method in surgical navigation, comprising: S1: in the vicinity of the skin of patient surgical site Fixed center easily identifiable marker, and the distal end of position sensor is coincided with the center of marker;S2: CT image scanning is carried out to patient along with marker;S3: the center coordinates of marker in the coordinate system of positioning system are obtained by position sensor;S4: the center of marker is obtained based on the result of automatic segmentation by carrying out the automatic segmentation of CT image to marker, determine the center coordinates of marker in the coordinate system of patient;S5: the conversion matrix of the coordinate system of positioning system and the coordinate system of patient is generated by the center coordinates of marker in the coordinate system of positioning system and the coordinate system of patient. Through high-density cross-line marker and marker automatic segmentation algorithm, marker center calculation method, the coordinate of marker in the coordinate system of patient can be accurately obtained.

Description

Technical Field

[0001] This invention relates to the technical field of automatic registration in surgical navigation, and more particularly to a method and system for automatic coordinate registration in surgical navigation. Background Technology

[0002] Surgical navigation systems accurately correlate preoperative or intraoperative imaging data with the patient's anatomical structures on the operating table. During surgery, they track surgical instruments and display their positions on the patient's images in real time as virtual probes. This allows doctors to clearly see the position of the surgical instruments relative to the patient's anatomical structures, making surgical or minimally invasive interventional procedures faster, more precise, and safer.

[0003] Surgical navigation systems typically include a navigation workstation, a positioning system, and surgical instruments. Currently, the surgical navigation market is dominated by optical and electromagnetic navigation systems. Optical navigation systems are primarily used in neurosurgery, orthopedics, spine surgery, and otolaryngology, while electromagnetic navigation systems are mainly used in thoracic and abdominal surgeries, such as those involving lung and liver tumors. Regardless of whether a surgical navigation system is based on electromagnetic or optical navigation, an essential step is coordinate registration between the patient's coordinate system and the positioning system's coordinate system.

[0004] Coordinate registration is based on a set of marker points and their corresponding coordinates in the patient's coordinate system and the positioning system's coordinate system. A transformation matrix between the two coordinate systems is generated using the LandMark method, thus establishing the mutual transformation relationship between them. In this way, the coordinates of the surgical instruments in the positioning system's coordinate system are obtained through positioning, and the transformation matrix is ​​used to convert the surgical instrument coordinates to the patient's coordinate system. This achieves matching of the surgical instruments and the patient's spatial structure in the same coordinate system, enabling visualized tracking and navigation of the surgical instruments' spatial relationship with the patient's body during surgery.

[0005] In actual surgery, markers are placed on the skin near the surgical site. The position of these markers must not interfere with the procedure. Current optical navigation systems primarily use manual coordinate registration and alignment. This involves calibrating the marker coordinates using a positioning pin within the positioning system, obtaining the marker's coordinates in the positioning system's coordinate system. The marker's coordinates in the patient's coordinate system are then manually obtained by locating the marker on the patient image using surgical planning software. This manual registration and alignment method is cumbersome and its accuracy is inconsistent, varying with each actual operation. With the development of electromagnetic navigation equipment, adding position sensors to the markers allows for automatic acquisition of the positioning system's coordinates. However, accurately obtaining the marker's coordinates in the patient's coordinate system remains a challenge. Currently, markers with regular shapes are primarily used, and their centroids are obtained to determine their coordinates in the patient's coordinate system. However, limitations imposed by CT image slice thickness and metal artifacts prevent the precise determination of the marker's centroid. This issue has consistently hindered the practical clinical application of coordinate alignment in surgical navigation products. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide an automatic coordinate registration method and system for surgical navigation. By using high-density crosshair markers, an automatic marker segmentation algorithm, and a marker center calculation method, the coordinates of the markers in the patient coordinate system can be accurately obtained.

[0007] The above-mentioned objective of this invention is achieved through the following technical solutions:

[0008] An automatic coordinate registration method for surgical navigation includes the following steps:

[0009] S1: Fix a centrally identifiable marker on the skin near the patient's surgical site, and align the distal end of the position sensor with the center of the marker;

[0010] S2: Perform a CT image scan on the patient along with the markers;

[0011] S3: Obtain the center coordinates of the marker in the positioning system coordinate system using the position sensor;

[0012] S4: By automatically segmenting the markers in the CT image and obtaining the center of the markers based on the automatic segmentation results, the center coordinates of the markers in the patient coordinate system are determined;

[0013] S5: Generate a transformation matrix between the positioning system coordinate system and the patient coordinate system using the center coordinates of the marker in the positioning system coordinate system and the patient coordinate system.

[0014] Furthermore, step S1 also includes:

[0015] The easily identifiable marker in the center is a cross marker. The cross marker is embedded in the marker base plate, and the cross marker, together with the marker base plate, is installed in the marker base.

[0016] The front of the marker base includes a marker slot, through which the cross marker and the marker base plate can be attached and detached. The back of the marker base is provided with double-sided adhesive, through which the cross marker is fixed to the skin near the patient's surgical site.

[0017] The far end of the position sensor is connected to the center of the cross marker, and the near end is connected to the host interface control unit (SIU) via a connecting line. At the same time, the position sensor and the base plate of the marker are relatively fixed.

[0018] Further, in step S4, the CT image is automatically segmented using the markers, specifically as follows:

[0019] Seed points are found by threshold segmentation: the segmentation threshold range is determined based on the CT value of the cross marker in the CT image, and all pixels in the CT image are traversed. Pixels whose CT value is within the segmentation threshold range are seed points.

[0020] Based on the seed point, tissue growth is performed to obtain the seed region: taking the seed point as the growth point, traversing the 26 neighborhoods of the seed point, and marking the pixels in the 26 neighborhoods whose CT values ​​are within the segmentation threshold range as the seed region, and taking the newly added pixels in the seed region as the new seed point, taking the new seed point as the growth point, and obtaining the seed region until all adjacent points are not within the segmentation threshold range.

[0021] Furthermore, after obtaining the seed region, cross-shaped line detection is performed within the seed region using a line template detection method. The selected seed region is then used as the cross-shaped marker in the CT image. Specifically:

[0022] Generate two mutually perpendicular line templates, wherein the length of each line template is the same as the length of one side of the cross mark;

[0023] The detection is performed with the pixel points in the seed region as the center of the line template, and the seed region that satisfies the cross marker feature is used as the candidate marker.

[0024] Among them, the cross marker features are that the two single sides are perpendicular to each other, the length of the single side line is close to the actual length of the object, and the error is less than two pixels.

[0025] Further, in step S4, the center of the marker is obtained based on the result of automatic segmentation, specifically as follows:

[0026] The seed region is identified as a boundary point. If a pixel in the seed region has a neighborhood of 26 that is not in the seed region, then the pixel in the current seed region is the boundary point.

[0027] Based on the current boundary point, the endpoints A, B, C and D of the cross marker are obtained by determining whether they are endpoints by the vector direction of the adjacent points outside the seed region and the current boundary point.

[0028] Obtain the line connecting endpoint A and endpoint B, and the line connecting endpoint C and endpoint C. The intersection of the two lines is the center of the marker.

[0029] Further, in step S5, the transformation matrix is ​​calculated using the LandMark method.

[0030] Furthermore, the cross marker is made of high-density material, is highlighted in the CT image, has two equal sides that are not less than 1 cm, forms a 90-degree angle with each side, and has a 45-degree angle between each side and the marker base. The marker base plate is made of low-density material and is distinguishable from the cross marker in the CT image. The marker base is fixed to the patient's skin, is rectangular, and has its long side parallel to the head-to-toe direction.

[0031] An automatic coordinate registration system for surgical navigation, used to perform the automatic coordinate registration method described above, includes:

[0032] A marker setting module is used to fix a centrally identifiable marker on the skin near the patient's surgical site, and to set the distal end of the position sensor to coincide with the center of the marker;

[0033] A CT imaging scanning module, used to perform CT image scanning on the patient along with the markers;

[0034] The positioning system coordinate system coordinate acquisition module is used to acquire the center coordinates of the marker in the positioning system coordinate system through the position sensor;

[0035] The patient coordinate system coordinate acquisition module is used to automatically segment the markers in the CT image and obtain the center of the markers based on the automatic segmentation results, and determine the center coordinates of the markers in the patient coordinate system.

[0036] The transformation matrix calculation module is used to generate a transformation matrix between the positioning system coordinate system and the patient coordinate system using the center coordinates of the marker in the positioning system coordinate system and the patient coordinate system.

[0037] A computer device includes a memory and one or more processors, the memory storing computer code that, when executed by the one or more processors, causes the one or more processors to perform the method described above.

[0038] A computer-readable storage medium storing computer code that, when executed, performs the method described above.

[0039] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0040] (1) A method for automatic coordinate registration in surgical navigation is provided, comprising the following steps: S1: fixing an easily identifiable marker on the skin near the surgical site of the patient, and setting the distal end of the position sensor to coincide with the center of the marker; S2: performing a CT image scan on the patient along with the marker; S3: obtaining the center coordinates of the marker in the coordinate system of the positioning system through the position sensor;

[0041] S4: By automatically segmenting the markers on the CT image and obtaining the center of the markers based on the automatic segmentation results, the center coordinates of the markers in the patient coordinate system are determined; S5: Using the center coordinates of the markers in the positioning system coordinate system and the patient coordinate system, a transformation matrix between the positioning system coordinate system and the patient coordinate system is generated. The above technical solution, through high-density crosshair markers, an automatic marker segmentation algorithm, and a marker center calculation method, can accurately obtain the coordinates of the markers in the patient coordinate system, improving the accuracy of coordinate registration.

[0042] (2) This application does not require manual coordinate registration and alignment, reducing the complexity of the operation during the operation.

[0043] (3) The cross markers are made of high-density material, which is not affected by the thickness of the CT scan image, can accurately obtain the center coordinates, and can easily perform automatic segmentation under CT images.

[0044] (4) The design of the marker base eliminates the need for the position sensor to be used as a consumable, thus reducing the clinical cost. Attached Figure Description

[0045] Figure 1 This is an overall flowchart of an automatic coordinate registration method for surgical navigation according to the present invention;

[0046] Figure 2 This is a schematic diagram of the cross-shaped marker of the present invention;

[0047] Figure 3 This is a schematic diagram of the base plate of the marker of the present invention;

[0048] Figure 4 This is a flowchart illustrating the process of obtaining the center coordinates of markers in the patient coordinate system according to the present invention.

[0049] Figure 5 This is a schematic diagram illustrating the acquisition of intersection points in this invention;

[0050] Figure 6 This is an overall structural diagram of an automatic coordinate registration method for surgical navigation according to the present invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0052] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0053] First Embodiment

[0054] like Figure 1 As shown, this embodiment provides a method for automatic coordinate registration in surgical navigation, including the following steps:

[0055] S1: Fix a centrally identifiable marker on the skin near the patient's surgical site, and align the distal end of the position sensor with the center of the marker.

[0056] Specifically, in this embodiment, such as Figure 2 As shown, the easily identifiable marker in the center is a cross-shaped marker. The cross-shaped marker is embedded into a marker base plate (preferably rectangular), and the cross-shaped marker, along with the marker base plate, is then installed in a... Figure 3The marker base shown includes a marker slot on its front side, through which the cross marker and its base plate can be attached and detached. Double-sided adhesive is provided on the back side of the marker base to fix the cross marker to the skin near the patient's surgical site. The distal end of the position sensor is connected to the center of the cross marker, and the proximal end is connected to the System Interface Unit (SIU) via a connecting cable. The position sensor and the base plate are relatively fixed in position.

[0057] Furthermore, the cross marker is made of a high-density material to ensure its high brightness in the CT image; a non-magnetic metal can be used. The two sides of the cross marker are equal in length and not less than 1 cm, forming a 90-degree angle. Each side of the cross marker forms a 45-degree angle with its base.

[0058] Furthermore, the base plate of the marker is made of a low-density material to distinguish it from the cross marker on the CT image; the use of metal is not recommended.

[0059] Furthermore, the marker base, fixed to the patient's skin, is rectangular, with its long side as parallel to the head-to-toe direction as possible, taking biocompatibility into consideration. The marker base is made of a low-density material, with a hardness sufficient to adhere to and tightly bond with human skin, preventing relative displacement. The marker base is a disposable consumable and requires on-site sterilization during clinical use. The marker base is used to mount the marker and must not have relative displacement with the marker; it is detachable. The marker base is approximately rectangular, about 3 cm long and 2 cm wide.

[0060] Furthermore, the position sensor must not be bent during assembly, must be fixed in position to the base plate, and must not undergo relative displacement. The outer layer of the position sensor connection cable is reinforced with an insulating layer, and the connection point with the base plate is treated to prevent breakage.

[0061] S2: Perform a CT image scan on the patient along with the markers.

[0062] Specifically, CT scans are performed on patients lying flat before or during surgery. The resulting CT images contain image data of markers.

[0063] S3: Obtain the center coordinates of the marker in the positioning system coordinate system using the position sensor.

[0064] Specifically, obtaining the center coordinates of a marker in the positioning system coordinate system is relatively simple; it can be read directly by the position sensor.

[0065] S4: By automatically segmenting the marker in the CT image and obtaining the center of the marker based on the result of the automatic segmentation, the center coordinates of the marker in the patient coordinate system are determined.

[0066] Step S4 is the core of this invention, such as Figure 4 As shown, the specific process includes the following refinement steps.

[0067] (1) Find seed points by threshold segmentation: Determine the segmentation threshold range based on the CT value of the cross marker in the CT image, and traverse all pixels of the CT image. Pixels whose CT value is within the segmentation threshold range are seed points.

[0068] Because the crosshair markers are made of high-density material and the marker base is made of low-density material, they are easily distinguishable on CT images by their CT values. In this embodiment, the segmentation threshold range is set to [1000, 65535]. All pixels in the CT image are traversed according to the segmentation threshold range, and pixels with CT values ​​within the set segmentation threshold range are recorded as seed points.

[0069] (2) Obtaining a seed region by tissue growth based on the seed point: Using the seed point as the growth point, traverse the 26 neighborhoods of the seed point. Pixels in the 26 neighborhoods whose CT values ​​are within the segmentation threshold range are marked as seed regions. The newly added pixels in the seed region are used as new seed points. Using the new seed points as growth points, the seed region is obtained until all adjacent points are not within the segmentation threshold range.

[0070] Specifically, when the segmentation threshold range is set to [1000, 65535], a seed region is obtained by tissue growth based on the seed point. Tissue growth satisfies the condition that pixels are connected and meet the threshold [1000, 65535]. The specific method is as follows: using the seed point as the growth point, pixels within the threshold range [1000, 65535] of the current seed point's 26 neighborhood are marked as seed regions and used as new seed points. The above steps are repeated until all adjacent points are no longer within the specified threshold range [1000, 65535].

[0071] (3) After obtaining the seed region, cross-shaped line detection is performed in the seed region based on the line template detection method to obtain the selected seed region as the cross-shaped marker in the CT image. Specifically, two mutually perpendicular line templates are generated, and the line templates have the same single-side length as the cross-shaped marker. The detection is performed with the pixel point in the seed region as the center of the line template, and the seed region that satisfies the cross-shaped marker characteristics is obtained as the candidate marker. Wherein, satisfying the cross-shaped marker characteristics means that the two single sides are mutually perpendicular, the single-side line length is close to the actual length, and the error is less than two pixels.

[0072] (4) Determine the boundary point of the seed region. If there is a pixel in the 26 neighborhood of a pixel in the seed region that is not in the seed region, then the pixel in the current seed region is the boundary point.

[0073] Specifically, the process iterates through all pixels in the seed region. For each pixel being iterated over, if there is a non-seed region pixel in the 26-neighborhood, then that pixel is considered part of the seed region. Once all pixels in the seed region have been traversed, all boundary points of the seed region can be obtained.

[0074] (5) Based on the current boundary point, determine whether it is an endpoint by the vector direction of the adjacent points outside the seed region and the current boundary point, and obtain the endpoints A, B, C, and D of the cross marker; Figure 5 As shown, the line connecting endpoint A and endpoint B, and the line connecting endpoint C and endpoint C are obtained, and the intersection of the two lines is the center of the marker.

[0075] Specifically, iterate through all boundary points and calculate the vector direction between the currently traversed boundary point and its adjacent points in the non-seed region. Determine if a point is an endpoint based on the direction of its vector. Generally, the vector of an endpoint should be parallel to the two sides of the crosshair marker.

[0076] S5: Generate a transformation matrix between the positioning system coordinate system and the patient coordinate system using the center coordinates of the marker in the positioning system coordinate system and the patient coordinate system.

[0077] Specifically, the transformation matrix is ​​calculated using the LandMark method.

[0078] Second Embodiment

[0079] like Figure 6 As shown, this embodiment provides an automatic coordinate registration system for surgical navigation used to perform the automatic coordinate registration method in surgical navigation as described in the first embodiment, comprising:

[0080] The marker setting module 1 is used to fix a centrally identifiable marker on the skin near the patient's surgical site, and to set the distal end of the position sensor to coincide with the center of the marker;

[0081] CT image scanning module 2 is used to perform CT image scanning on the patient together with the markers;

[0082] The positioning system coordinate system coordinate acquisition module is used to acquire the center coordinates of the marker in the positioning system coordinate system through the position sensor;

[0083] The patient coordinate system coordinate acquisition module 3 is used to automatically segment the marker in the CT image and obtain the center of the marker based on the result of the automatic segmentation, and determine the center coordinates of the marker in the patient coordinate system.

[0084] The transformation matrix calculation module 4 is used to generate a transformation matrix between the positioning system coordinate system and the patient coordinate system using the center coordinates of the marker in the positioning system coordinate system and the patient coordinate system.

[0085] A computer-readable storage medium stores computer code that, when executed, performs the methods described above. Those skilled in the art will understand that all or part of the steps in the various methods of the above embodiments can be implemented by a program instructing related hardware. This program can be stored in a computer-readable storage medium, which may include: read-only memory (ROM), random access memory (RAM), a magnetic disk, or an optical disk, etc.

[0086] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

[0087] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0088] It should be noted that the above embodiments can be freely combined as needed. The above description is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for automatic coordinate registration in surgical navigation, characterized in that, Includes the following steps: S1: Fix a centrally identifiable marker on the skin near the patient's surgical site, and align the distal end of the position sensor with the center of the marker; S2: Perform a CT image scan on the patient along with the markers; S3: Obtain the center coordinates of the marker in the positioning system coordinate system using the position sensor; S4: By automatically segmenting the markers in the CT image and obtaining the center of the markers based on the automatic segmentation results, the center coordinates of the markers in the patient coordinate system are determined; In step S4, the markers are automatically segmented in the CT image, specifically as follows: Seed points are found by threshold segmentation: the segmentation threshold range is determined based on the CT value of the cross marker in the CT image, and all pixels of the CT image are traversed. Pixels whose CT value is within the segmentation threshold range are seed points. Based on the seed point, tissue growth is performed to obtain the seed region: taking the seed point as the growth point, traversing the 26 neighborhoods of the seed point, and marking the pixels in the 26 neighborhoods whose CT values ​​are within the segmentation threshold range as the seed region, and taking the newly added pixels in the seed region as the new seed point, taking the new seed point as the growth point to obtain the seed region, until all adjacent points are not within the segmentation threshold range. After obtaining the seed region, cross-shaped line detection is performed within the seed region using a line template detection method. The resulting filtered seed region serves as the cross-shaped marker in the CT image. Specifically: Generate two mutually perpendicular line templates, wherein the length of each line template is the same as the length of one side of the cross mark; The detection is performed with the pixel points in the seed region as the center of the line template, and the seed region that satisfies the cross marker feature is used as the candidate marker. Among them, the cross marker features are that the two single sides are perpendicular to each other, the length of the single side line is close to the actual length of the object, and the error is less than two pixels. In step S4, the center of the marker is obtained based on the result of automatic segmentation, specifically: The seed region is identified as a boundary point. If a pixel in the seed region has a neighborhood of 26 that is not in the seed region, then the pixel in the current seed region is the boundary point. Based on the current boundary point, the endpoints A, B, C and D of the cross marker are obtained by determining whether they are endpoints by the vector direction of the adjacent points outside the seed region and the current boundary point. Obtain the line connecting endpoint A and endpoint B, and the line connecting endpoint C and endpoint C. The intersection of the two lines is the center of the marker. S5: Generate a transformation matrix between the positioning system coordinate system and the patient coordinate system using the center coordinates of the marker in the positioning system coordinate system and the patient coordinate system.

2. The automatic coordinate registration method for surgical navigation according to claim 1, characterized in that, Step S1 also includes: The easily identifiable marker in the center is a cross marker. The cross marker is embedded in the marker base plate, and the cross marker, together with the marker base plate, is installed in the marker base. The front of the marker base includes a marker slot, through which the cross marker and the marker base plate can be attached and detached. The back of the marker base is provided with double-sided adhesive, which is used to fix the cross marker to the skin near the patient's surgical site. The far end of the position sensor is connected to the center of the cross marker, and the near end is connected to the host interface control unit (SIU) via a connecting line. At the same time, the position sensor and the base plate of the marker are relatively fixed.

3. The automatic coordinate registration method for surgical navigation according to claim 1, characterized in that, Also includes: In step S5, the transformation matrix is ​​calculated using the LandMark method.

4. The automatic coordinate registration method for surgical navigation according to claim 2, characterized in that, Also includes: The cross marker is made of high-density material, the cross marker is highlighted in the CT image, the two sides of the cross marker are equal and not less than 1 cm, the two sides form a 90-degree angle, and the one side of the cross marker forms a 45-degree angle with the marker base. The marker base plate is made of a low-density material, which distinguishes it from the cross marker on the CT image. The marker base is fixed to the patient's skin and is rectangular, with its long side parallel to the head-to-toe direction.

5. An automatic coordinate registration system for surgical navigation for performing the automatic coordinate registration method for surgical navigation as described in any one of claims 1-4, comprising: A marker setting module is used to fix a centrally identifiable marker on the skin near the patient's surgical site, and to set the distal end of the position sensor to coincide with the center of the marker; A CT imaging scanning module, used to perform CT image scanning on the patient along with the markers; The positioning system coordinate system coordinate acquisition module is used to acquire the center coordinates of the marker in the positioning system coordinate system through the position sensor; The patient coordinate system coordinate acquisition module is used to automatically segment the markers in the CT image and obtain the center of the markers based on the automatic segmentation results, and determine the center coordinates of the markers in the patient coordinate system. The transformation matrix calculation module is used to generate a transformation matrix between the positioning system coordinate system and the patient coordinate system using the center coordinates of the marker in the positioning system coordinate system and the patient coordinate system.

6. A computer device comprising a memory and one or more processors, the memory storing computer code that, when executed by the one or more processors, causes the one or more processors to perform the method as described in any one of claims 1 to 4.

7. A computer-readable storage medium storing computer code, wherein when the computer code is executed, the method of any one of claims 1 to 4 is performed.

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