Transverse process positioning method and device, computer equipment and storage medium

Abstract

The invention relates to the technical field of medical imaging, in particular to a transverse process positioning method and device, computer equipment and a storage medium. The method comprises the following steps: scanning the transverse process center of a target object from a plurality of directions to obtain a first coordinate of each transverse process center in each direction; performing principal component analysis and clustering analysis based on the first coordinates to obtain a clustering center of each vertebra; according to the second coordinate of each transverse process in the ultrasonic image of the target object and the coordinate of the clustering center, determining a target center closest to the transverse process from the clustering center; the first coordinates and the second coordinates are three-dimensional coordinates; and determining the vertebra corresponding to the target center as the vertebra where the transverse process is located. By adopting the method, the vertebrae where the transverse process is located can be accurately positioned.

Description

Technical Field

[0001] The present application relates to the field of medical imaging technology, and in particular to a transverse process positioning method, apparatus, computer equipment, and storage medium. Background Art

[0002] With the development of medical technology, image registration technology has emerged. Image registration technology is mainly used to merge images from different imaging modalities, thereby providing richer information to help doctors make diagnoses. For example, when merging images from different imaging modalities, it is necessary to perform image registration based on the common features in the images from different imaging modalities.

[0003] When performing image registration of vertebrae, image registration can be performed based on the transverse process position information in ultrasound images and medical images. However, since ultrasound probes cannot simultaneously detect the transverse processes of all vertebrae, it is impossible to determine the vertebra where the transverse process detected by the ultrasound probe is located. Summary of the Invention

[0004] Based on this, it is necessary to provide a transverse process positioning method, device, computer equipment and storage medium that can accurately position the transverse process in order to address the above technical problems.

[0005] In a first aspect, the present application provides a transverse process positioning method, the method comprising: Scanning the transverse process center of the target object from multiple directions to obtain a first coordinate of each transverse process center in each direction; Performing principal component analysis and cluster analysis based on each of the first coordinates to obtain a cluster center for each vertebra; determining, from the cluster centers, a target center closest to the transverse process according to the second coordinates of each transverse process in the ultrasound image of the target object and the coordinates of the cluster centers, wherein both the first coordinates and the second coordinates are three-dimensional coordinates; The vertebra corresponding to the target center is determined as the vertebra where the transverse process is located.

[0006] In one embodiment, scanning the transverse process center of the target object from multiple directions to obtain the first coordinate of each transverse process center in each direction includes: Determine the transverse process center of the target object; Scanning the center of each transverse process from multiple directions using an ultrasonic probe to obtain the two-dimensional coordinates of the center of each transverse process in each direction; The two-dimensional coordinates of the center of each transverse process in each direction are converted into first coordinates in the electromagnetic space.

[0007] In one embodiment, determining the center of the transverse process of each vertebra of the target object includes: Segmenting a first transverse process image of a plurality of transverse processes from an ultrasound image of a vertebral region of the target object; Binarizing the first transverse process image to obtain a binary image, and identifying the edge contour of each transverse process in the binary image; The centroid of the edge contour is determined as the center of the transverse process of the target vertebra, or a circumscribed figure containing the edge contour is determined, and the center of the circumscribed figure is determined as the center of the transverse process of the target vertebra.

[0008] In one embodiment, performing principal component analysis and cluster analysis based on each of the first coordinates to obtain the cluster center of each vertebra includes: constructing a data matrix based on each of the first coordinates, and performing centralization processing on the data matrix to obtain a centralized matrix; Calculating a covariance matrix of the centralization matrix, and calculating eigenvalues ​​of the covariance matrix and eigenvectors corresponding to the eigenvalues; Taking the eigenvector corresponding to the maximum eigenvalue as the projection axis, projecting each of the first coordinates onto the projection axis to obtain a third coordinate after each of the first coordinates is projected; Cluster analysis is performed based on each of the third coordinates to obtain a cluster center of each vertebra.

[0009] In one embodiment, the method further comprises: Sort the cluster centers according to their coordinate sizes on the projection axis; According to the ranking results of the cluster centers, the vertebrae corresponding to the cluster centers are determined.

[0010] In one embodiment, determining the target center closest to the transverse process from the cluster centers based on the second coordinates of each transverse process in the ultrasound image of the target object and the coordinates of the cluster centers includes: a second transverse process image segmenting a plurality of transverse processes from an ultrasound image of a vertebral region of the target subject; determining the two-dimensional coordinates of each transverse process in the second transverse process image, and converting the two-dimensional coordinates into second coordinates in electromagnetic space; performing centralization processing on the second coordinate to obtain a centralized second coordinate; Projecting the centralized second coordinate onto the projection principal axis to obtain the fourth coordinate of each transverse process after projection; Based on each of the fourth coordinates, a target center closest to each of the transverse processes is determined from the cluster centers.

[0011] In one embodiment, the method further comprises: Segmenting a third transverse process image from a medical image of the vertebral portion of the target subject, and determining the vertebra where each transverse process in the third transverse process image is located; determining the transverse processes of the same vertebra in the second transverse process image and the third transverse process image as a transverse process pair; registering the ultrasound image and the medical image according to the three-dimensional coordinate information of each transverse process in the transverse process pair to obtain a registration matrix; Based on the registration matrix, a cross-sectional image of the ultrasound image in the three-dimensional reconstructed model corresponding to the medical image is determined, so as to perform puncture guidance based on the cross-sectional image and the ultrasound image.

[0012] In a second aspect, the present application provides a transverse process positioning device, comprising: A scanning module, configured to scan the transverse process center of the target object from multiple directions to obtain a first coordinate of each transverse process center in each direction; an analysis module, configured to perform principal component analysis and cluster analysis based on each of the first coordinates to obtain a cluster center of each vertebra; a center determination module, configured to determine, from the cluster centers, a target center closest to the transverse process based on the second coordinates of each transverse process in the ultrasound image of the target object and the coordinates of the cluster centers; wherein both the first coordinates and the second coordinates are three-dimensional coordinates; A positioning module is used to determine the vertebra corresponding to the target center as the vertebra where the transverse process is located.

[0013] In a third aspect, the present application provides a computer device comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0014] In a fourth aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, which implements the steps of the above method when executed by a processor.

[0015] The above-mentioned transverse process positioning method, apparatus, computer equipment and storage medium scan the transverse process center of the target object from multiple directions to obtain the first coordinate of each transverse process center in each direction, and perform principal component analysis and cluster analysis based on each first coordinate to obtain the cluster center of each vertebra. This can avoid the error caused by a single perspective and facilitate more accurate determination of the cluster center of each vertebra. The target center closest to the transverse process is determined from the cluster center based on the second coordinates of each transverse process and the coordinates of the cluster center in the ultrasound image of the target object; the first coordinate and the second coordinate are both three-dimensional coordinates, and the vertebra corresponding to the target center is determined as the vertebra where the transverse process is located. This can reduce the data dimension while retaining the main features of the data, so as to improve the positioning accuracy of the transverse process and accurately locate the vertebra where the transverse process is located. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A diagram showing an application environment of a transverse process positioning method according to an embodiment; Figure 2 Schematic diagram of a process of locating a transverse process according to an embodiment; Figure 3 A schematic diagram of a process for lumbar vertebrae alignment according to one embodiment; Figure 4 is a structural block diagram of a transverse process positioning device in one embodiment; Figure 5 FIG. 1 is a diagram showing the internal structure of a computer device in one embodiment. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0018] The transverse process positioning method provided in the embodiment of the present application can be applied to Figure 1 In the application environment shown. Among them, the console 102 and the terminal 104 are connected. The console 102 can be a device for transverse process positioning, or a system for transverse process positioning. The console 102 scans the transverse process center of the target object from multiple directions to obtain the first coordinates of each transverse process center in each direction; the console 102 performs principal component analysis and cluster analysis based on each first coordinate to obtain the cluster center of each vertebra; the console 102 determines the target center closest to the transverse process from the cluster center based on the second coordinates of each transverse process and the coordinates of the cluster center in the ultrasound image of the target object; the first coordinate and the second coordinate are both three-dimensional coordinates; the console 102 determines the vertebra corresponding to the target center as the vertebra where the transverse process is located.

[0019] In one embodiment, Figure 2 As shown, a transverse process positioning method is provided, which is applied to Figure 1 The following steps are used as an example to illustrate the console in the figure: S202 , scanning the transverse process centers of the target object from multiple directions to obtain first coordinates of each transverse process center in each direction.

[0020] The transverse process center refers to the center point of each transverse process in the vertebrae of the target subject. The transverse process center can be obtained by identifying an image of the vertebrae of the target subject. The vertebrae can be the lumbar or thoracic vertebrae of the target subject. If the vertebrae are in the lumbar region, the transverse process center is the center point of each transverse process in the lumbar region. If the vertebrae are in the thoracic region, the transverse process center is the center point of each rib in the thoracic region.

[0021] Scanning the transverse process center can be achieved using an ultrasound probe. When the ultrasound probe moves, the coordinates of the same transverse process center on different scanning planes will deviate. Therefore, scanning the transverse process center of the target object from multiple directions can reduce the error caused by scanning.

[0022] The first coordinate is a three-dimensional coordinate in electromagnetic space. Each transverse process center has a first coordinate in all directions, and these first coordinates may or may not be consistent. After the ultrasound probe scans the transverse process center, the two-dimensional coordinates of the transverse process center are first obtained. These two-dimensional coordinates are then converted into three-dimensional first coordinates using a transformation matrix. The transformation matrix converts the ultrasound plane to electromagnetic coordinates.

[0023] Optionally, the console controls the ultrasound probe to scan the transverse process center of the target object from multiple directions to obtain the first coordinates of each transverse process center in each direction.

[0024] S204 , performing principal component analysis and cluster analysis based on each first coordinate to obtain a cluster center of each vertebra.

[0025] Principal component analysis (PCA) is a statistical procedure that transforms a set of potentially correlated variables into a set of linearly independent variables through an orthogonal transformation. These new variables are called principal components. Principal components are linear combinations of the original variables and are ordered by variance: the first principal component has the largest variance, the second has the second largest variance, and so on. The main goal of PCA is dimensionality reduction—reducing the dimensionality of a dataset while preserving as much variation as possible in the original data. This helps simplify data analysis, improves computational efficiency, and removes noise and redundant information.

[0026] Cluster analysis is a technique used to partition a dataset into multiple groups or clusters, so that objects within the same cluster are more similar to each other than objects in other clusters. Clustering algorithms include, but are not limited to, K-means clustering and hierarchical clustering.

[0027] The vertebra is part of the target subject's spine. Vertebrae can be either lumbar or thoracic. Lumbar vertebrae include the vertebral body, vertebral arch, and the transverse processes, spinous processes, superior articular processes, and inferior articular processes extending from the vertebral arch. Thoracic vertebrae include the vertebral body, pedicles, lamina, vertebral foramen, spinous processes, articular processes, and transverse processes. The cluster center of each vertebra can be determined by sorting the coordinates of the cluster centers. Specifically, the vertebra corresponding to each cluster center is determined based on the sorted coordinates of the cluster centers.

[0028] Optionally, the console performs a principal component analysis based on each first coordinate, and then performs a cluster analysis based on the result of the principal component analysis to obtain a cluster center of each vertebra.

[0029] S206 , determining the target center closest to the transverse process from the cluster centers according to the second coordinates of each transverse process in the ultrasound image of the target object and the coordinates of the cluster centers; the first coordinate and the second coordinate are both three-dimensional coordinates.

[0030] The second coordinate is a three-dimensional coordinate in electromagnetic space. After the ultrasound probe scans the center of the transverse process, the two-dimensional coordinate of the transverse process can be obtained first, and then the two-dimensional coordinate is converted into a three-dimensional second coordinate through the transformation matrix.

[0031] Each transverse process corresponds to a target center. For example, if there are transverse processes 1, 2, and 3 in the ultrasound image, and calculations show that cluster center 1 is closest to transverse process 1, cluster center 2 is closest to transverse process 2, and cluster center 3 is closest to transverse process 3, then cluster center 1 is the target center for transverse process 1, cluster center 2 is the target center for transverse process 2, and cluster center 3 is the target center for transverse process 3.

[0032] Optionally, the console calculates the distance between each transverse process and each cluster center according to the second coordinates of each transverse process and the coordinates of the cluster center in the ultrasound image of the target object, and determines the cluster center closest to the transverse process as the target center corresponding to the transverse process.

[0033] S208: Determine the vertebra corresponding to the target center as the vertebra where the transverse process is located.

[0034] There are five lumbar vertebrae in the human body, namely the first lumbar vertebra, the second lumbar vertebra, the third lumbar vertebra, the fourth lumbar vertebra and the fifth lumbar vertebra. The lumbar vertebrae are connected in sequence. Figure 3As shown, L1 represents the first lumbar vertebra, L2 the second lumbar vertebra, L3 the third lumbar vertebra, L4 the fourth lumbar vertebra, and L5 the fifth lumbar vertebra. The human body has 12 thoracic vertebrae, designated as T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, and T12. The vertebra where each transverse process is located refers to the vertebral position of the transverse process in the target subject, such as the lumbar or thoracic vertebra.

[0035] The vertebra corresponding to the target center is the vertebra corresponding to the cluster center. For example, cluster center 1 corresponds to the vertebra where transverse process 1 is located, cluster center 2 corresponds to the vertebra where transverse process 2 is located, and cluster center 3 corresponds to the vertebra where transverse process 3 is located.

[0036] Optionally, the console determines the vertebra corresponding to each target center as the vertebra where the transverse process is located.

[0037] In the above-mentioned transverse process positioning method, the transverse process center of the target object is scanned from multiple directions to obtain the first coordinates of each transverse process center in each direction. Principal component analysis and cluster analysis are performed based on each first coordinate to obtain the cluster center of each vertebra. This can avoid the error caused by a single perspective and facilitate more accurate determination of the cluster center of each vertebra. The target center closest to the transverse process is determined from the cluster center based on the second coordinates of each transverse process and the coordinates of the cluster center in the ultrasound image of the target object; the first coordinate and the second coordinate are both three-dimensional coordinates, and the vertebra corresponding to the target center is determined as the vertebra where the transverse process is located. This can reduce the data dimension while retaining the main features of the data, so as to improve the positioning accuracy of the transverse process and accurately locate the vertebra where each transverse process is located.

[0038] In one embodiment, scanning the transverse process centers of the target object from multiple directions to obtain the first coordinates of each transverse process center in each direction includes: Determine the center of the transverse process of the target object.

[0039] An ultrasonic probe is used to scan the center of each transverse process from multiple directions to obtain the two-dimensional coordinates of the center of each transverse process in each direction.

[0040] The two-dimensional coordinates of the center of each transverse process in each direction are converted into the first coordinates in the electromagnetic space.

[0041] The transverse process center is the center point of the transverse process, which can be obtained through a target image including each vertebra of the vertebral part of the target object, or can be obtained by an operator manually identifying the target image and sending the result of the manual identification to the console.

[0042] The conversion of the two-dimensional coordinates of the center of the transverse process into the first coordinates of the electromagnetic space can be achieved by the transformation matrix. Specifically, the two-dimensional coordinates of the center of the transverse process are P ( x , y ), T w is the transformation matrix from ultrasonic plane to electromagnetic space, through , the two-dimensional coordinates of the center of the transverse process can be converted into the first coordinates of the three-dimensional form ( x w , y w , z w ).

[0043] Optionally, the console determines the center of a transverse process of the target object and scans each transverse process center of the target object from multiple directions using an ultrasound probe to obtain the two-dimensional coordinates of each transverse process center in each direction. The console obtains a transformation matrix from the ultrasound plane to electromagnetic space and uses the transformation matrix to convert the two-dimensional coordinates of each transverse process center in each direction into a first coordinate in the electromagnetic space.

[0044] In this embodiment, each transverse process center is scanned from multiple directions and the two-dimensional coordinates are converted into first coordinates in the electromagnetic space, so that the precise positioning of the transverse process center in the three-dimensional space can be achieved.

[0045] In one embodiment, determining the center of the transverse process of each vertebra of the target subject includes: segmenting a first transverse process image of a plurality of transverse processes from an ultrasound image of a vertebral region of the target subject; Binarizing the first transverse process image to obtain a binary image, and identifying the edge contour of each transverse process in the binary image; The centroid of the edge contour is determined as the center of the transverse process of the target vertebra, or a circumscribed figure containing the edge contour is determined, and the center of the circumscribed figure is determined as the center of the transverse process of the target vertebra.

[0046] The ultrasound image is obtained by scanning the vertebral part of the target object with an ultrasound probe. The method of segmenting the first transverse process image from the ultrasound image includes but is not limited to the threshold segmentation method, the edge detection method, the region generation method, the model segmentation method, etc. The method of segmenting the first transverse process image from the ultrasound image can also be a combination of multiple methods including the threshold segmentation method, the edge detection method, and the model segmentation method. The threshold segmentation method is to divide the pixels in the image into several parts by setting one or more thresholds, so as to segment the first transverse process image and other tissues in the ultrasound image by pixel values. The edge detection method is to use the edge detection algorithm to identify the edge contour of the transverse process in the image, so as to locate and segment the first transverse process image by the edge contour. The model-based method is to use a trained segmentation model to segment the first transverse process image from the ultrasound image.

[0047] Binarization is an image processing technique used to convert a grayscale or color image into a black and white image, where each pixel has a value of either 0 or 255. Binarization is typically performed based on a threshold. Specifically, if the grayscale value of a pixel is greater than the threshold, the pixel is set to 255; if the pixel is less than or equal to the threshold, the pixel is set to 0. The edge contours of each transverse process in the binarized image can be identified using image processing techniques.

[0048] The centroid of the edge contour can be determined based on the average coordinates of all points within the contour. Circumscribed graphics include but are not limited to circumscribed circles and circumscribed rectangles.

[0049] In some embodiments, the centroid of the edge contour may be determined as a first center of the target vertebra, a circumscribed figure containing the edge contour may be determined, the center of the circumscribed figure may be determined as a second center of the target vertebra, and the transverse process center of the vertebra may be determined based on the first and second centers. Specifically, the transverse process center of the vertebra may be determined based on the average coordinates of the first and second centers.

[0050] Optionally, the console segments a first transverse process image of multiple transverse processes from an ultrasound image of the vertebral region of the target subject using one or more segmentation methods. The console binarizes the segmented first transverse process image to obtain a binary image. The console identifies the edge contours of each transverse process in the binary image and determines the center of mass of the edge contours using the average coordinates of all points within the edge contours. The console determines the center of mass of the edge contours as the center of the transverse process of the target subject's vertebra, or determines a circumscribed figure containing the edge contours and determines the center of the circumscribed figure as the center of the transverse process of the target subject's vertebra.

[0051] In this embodiment, by binarizing the first transverse process image and identifying the edge contours of each transverse process in the binarized image, the transverse process boundaries can be effectively highlighted, the influence of background noise can be reduced, and the extent of the transverse process can be more clearly and accurately defined. By determining the centroid of the edge contour or the center of the circumscribed figure as the transverse process center, the transverse process center can be determined for transverse processes of different shapes, improving the consistency and accuracy of positioning.

[0052] In one embodiment, principal component analysis and cluster analysis are performed based on each first coordinate to obtain the cluster center of each vertebra, including: A data matrix is ​​constructed based on each first coordinate, and the data matrix is ​​centralized to obtain a centralized matrix.

[0053] Calculate the covariance matrix of the centered matrix and calculate the eigenvalues ​​of the covariance matrix and the eigenvectors corresponding to the eigenvalues.

[0054] The eigenvector corresponding to the maximum eigenvalue is used as the projection axis, and each first coordinate is projected onto the projection axis to obtain a third coordinate after each first coordinate is projected.

[0055] Cluster analysis was performed based on each third coordinate to obtain the cluster center of each vertebra.

[0056] Each row in the data matrix is ​​determined by a first coordinate. Specifically, the data matrix middle( x n , y n , z n ) indicates the n The first coordinate.

[0057] The centering process includes: calculating the average value of each column in the data matrix to obtain the mean vector, calculating the difference between the data matrix and the mean vector to obtain the centering matrix. Specifically, the centering matrix , X is the data matrix, is the mean vector.

[0058] The formula for calculating the covariance matrix is , C is the covariance matrix, n is the number of the first coordinate, X c is the centralized matrix, is the transposed matrix of the centered matrix.

[0059] The eigenvalues ​​and the eigenvectors corresponding to the eigenvalues ​​are obtained by singular value decomposition of the covariance matrix. Specifically, the singular value decomposition covariance matrix is ,V is the eigenvector matrix, is the transposed matrix of the eigenvector matrix, is a diagonal matrix containing the eigenvalues.

[0060] The calculation formula for the third coordinate is, , V 1 is the projection axis, X c is the centralized matrix, X p is the third coordinate.

[0061] Optionally, the console constructs a data matrix based on the multiple first coordinates X , calculate the mean value of each column in the data matrix and get the mean vector , calculate the data matrix X Subtract the mean vector The difference between X c The console calculates the covariance matrix of the centralization matrix and decomposes the covariance matrix through singular value decomposition C , and get the covariance matrix C The eigenvalues ​​and eigenvectors corresponding to each eigenvalue. The console uses the eigenvector corresponding to the maximum eigenvalue as the projection axis. V 1. Project each first coordinate onto the projection axis V 1. Get the third coordinate after projection of each first coordinate The console is based on each third coordinate X p Cluster analysis was performed to obtain the cluster center of each vertebra.

[0062] In this embodiment, by using the eigenvector corresponding to the maximum eigenvalue as the projection axis, the main variation direction in the data can be captured, which helps to filter out noise and emphasize the main pattern of the data, thereby improving the accuracy of the third coordinate estimation and thus improving the accuracy of the cluster center.

[0063] In one embodiment, the transverse process positioning method further comprises: Sort the cluster centers according to their coordinate sizes on the projection axis.

[0064] According to the sorting results of each cluster center, the vertebra corresponding to each cluster center is determined.

[0065] In some embodiments, the direction of the projection axis is the direction from the foot to the head of the target object. Since the vertebrae are arranged in sequence from the head to the foot of the target object, the direction from the foot to the head of the target object is used as the direction of the projection axis. The cluster centers are sorted according to the coordinate size of each cluster center on the projection axis to determine the vertebrae where each cluster center is located, which can improve accuracy. Furthermore, according to the coordinate value of each cluster center on the projection axis, the cluster centers are sorted from low to high to obtain the sorting results of each cluster center. Among them, the cluster center with a smaller coordinate value is located at the bottom, close to the foot of the target object, and the cluster center with a larger coordinate value is located at the top, close to the head of the target object. Specifically, if the vertebra is a lumbar vertebra, the lumbar vertebrae corresponding to each cluster center in the sorting result are the fifth lumbar vertebra, the fourth lumbar vertebra, the third lumbar vertebra, the second lumbar vertebra and the first lumbar vertebra, that is, the cluster center ranked first corresponds to the fifth lumbar vertebra, the cluster center ranked second corresponds to the fourth lumbar vertebra, the cluster center ranked third corresponds to the third lumbar vertebra, the cluster center ranked fourth corresponds to the second lumbar vertebra, and the cluster center ranked fifth corresponds to the first lumbar vertebra.

[0066] Optionally, the console sorts the cluster centers from low to high according to the coordinate value of each cluster center on the projection axis to obtain a sorting result of each cluster center.

[0067] In this embodiment, by sorting the coordinates of the cluster centers on the projection axis, the cluster centers in different vertebral segments can be more clearly identified and distinguished, which helps to avoid confusion between the cluster centers of adjacent vertebrae, thereby accurately guiding the puncture needle or anesthesia needle for puncture in the puncture scenario.

[0068] In one embodiment, determining the target center closest to the transverse process from the cluster centers based on the second coordinates of each transverse process in the ultrasound image of the target object and the coordinates of the cluster centers includes: A second transverse process image is obtained by segmenting a plurality of transverse processes from the ultrasound image of the vertebral region of the target subject.

[0069] The two-dimensional coordinates of each transverse process in the second transverse process image are determined, and the two-dimensional coordinates are converted into second coordinates in the electromagnetic space.

[0070] The second coordinate is centralized to obtain a centralized second coordinate.

[0071] The centralized second coordinate is projected onto the projection axis to obtain the fourth coordinate of each transverse process.

[0072] Based on each fourth coordinate, the target center closest to each transverse process is determined from the cluster centers.

[0073] Among them, the method of segmenting the second transverse process image from the ultrasound image includes but is not limited to the threshold segmentation method, the edge detection method, the region generation method, the model segmentation method, etc. The method of segmenting the second transverse process image from the ultrasound image can also be a combination of multiple methods including the threshold segmentation method, the edge detection method, and the model segmentation method. The threshold segmentation method is to divide the pixels in the image into several parts by setting one or more thresholds, so as to segment the second transverse process image and other tissues in the ultrasound image by pixel values. The edge detection method is to use the edge detection algorithm to identify the edge contour of the transverse process in the image, so as to locate and segment the second transverse process image by the edge contour. The model-based method is to use a trained segmentation model to segment the second transverse process image from the ultrasound image.

[0074] The two-dimensional coordinates are obtained by scanning with an ultrasound probe. After the ultrasound probe scans the transverse process, the two-dimensional coordinates of the transverse process are first obtained. These two-dimensional coordinates are then converted into a second three-dimensional coordinate using a transformation matrix. The transformation matrix converts the ultrasound plane into electromagnetic space.

[0075] The centralization process includes: determining a target data matrix composed of each second coordinate, calculating the average value of each column in the target data matrix to obtain a target mean vector, calculating the difference between the target data matrix and the target mean vector to obtain the centralized second coordinate.

[0076] In some embodiments, the first coordinate can be directly centered to obtain a centered first coordinate, and the centered first coordinate can be projected onto the projection axis to obtain a fourth coordinate of each transverse process. This can save time in obtaining the second coordinate and improve the efficiency of transverse process positioning.

[0077] Optionally, the console segments a second transverse process image of a plurality of transverse processes from an ultrasound image of the vertebral region of the target subject. The console determines the two-dimensional coordinates of each transverse process in the second transverse process image and converts the two-dimensional coordinates into second coordinates in electromagnetic space. The console performs centralization processing on the second coordinates to obtain a centralized second coordinate. The console projects the centralized second coordinates onto the projection principal axis to obtain a fourth coordinate of each transverse process after projection; the console calculates the distance between each fourth coordinate and each cluster center, and determines the target center closest to each transverse process from the cluster center based on the calculation results.

[0078] In this embodiment, based on each fourth coordinate, the target center closest to each transverse process is determined from the cluster centers previously obtained through cluster analysis. This method not only improves the accuracy of transverse process positioning, but also can effectively identify and distinguish different vertebral segments, so that high reliability can be maintained even in complex anatomical environments.

[0079] In one embodiment, the transverse process positioning method further comprises: A third transverse process image is segmented from a medical image of a vertebral portion of a target object, and the vertebra where each transverse process in the third transverse process image is located is determined.

[0080] The transverse processes of the second transverse process image and the third transverse process image in the same vertebra are identified as a transverse process pair.

[0081] According to the three-dimensional coordinate information of each transverse process in the transverse process pair, the ultrasound image and the medical image are registered to obtain a registration matrix.

[0082] Based on the registration matrix, a cross-sectional image of the ultrasound image in the three-dimensional reconstructed model corresponding to the medical image is determined, so as to perform puncture guidance based on the cross-sectional image and the ultrasound image.

[0083] The medical image is static image data capturing the vertebral region of the target subject at a specific moment. Medical images include, but are not limited to, computed tomography, magnetic resonance imaging, and positron emission tomography. Methods for segmenting the third transverse process image from the medical image include, but are not limited to, threshold segmentation, edge detection, region generation, and model segmentation. Segmenting the third transverse process image from the medical image may also be a combination of multiple methods including threshold segmentation, edge detection, and model segmentation.

[0084] Due to the limited detection range of the ultrasound probe's detection window, ultrasound images do not capture all transverse processes of the target vertebrae. Medical imaging, on the other hand, is a comprehensive scan of the target vertebrae, capturing all transverse processes. Therefore, the third transverse process image will contain more transverse processes than the first and second transverse process images. For example, there are five lumbar vertebrae in the human body, each with a transverse process. An ultrasound probe can only detect three consecutive lumbar vertebrae, while magnetic resonance imaging can capture all five lumbar vertebrae. Therefore, the first transverse process image will contain three transverse processes, while the second transverse process image will contain five.

[0085] In some embodiments, because the third transverse process image may include each transverse process of the target subject's vertebrae, the transverse processes in the third transverse process image can be sorted based on their three-dimensional coordinate information, and the vertebrae to which each transverse process in the third transverse process image resides can be determined based on the sorting result. Specifically, the transverse processes are sorted based on their coordinate values ​​on the target axis, and the vertebrae to which each transverse process in the third transverse process image resides can be determined based on the sorting result. The target axis is oriented from the foot to the head of the target subject.

[0086] In some embodiments, the vertebrae to which each transverse process in the third transverse process image is located can also be determined based on the morphological characteristics of the transverse process and / or adjacent structures. For example, in the lumbar vertebrae, the transverse process of the third lumbar vertebra is typically longer, being the longest transverse process of all lumbar vertebrae. Therefore, the longest transverse process in the third transverse process image can be determined as the transverse process of the third lumbar vertebra. The transverse process of the fifth lumbar vertebra is typically thicker and extends bilaterally, forming a lumbosacral joint with the sacrum. Therefore, the thicker and more bilaterally extending transverse process in the third transverse process image can be determined as the transverse process of the fifth lumbar vertebra. The transverse process of the fifth lumbar vertebra is connected to the sacrum, forming a lumbosacral angle. Therefore, the transverse process connected to the sacrum can also be determined as the transverse process of the fifth lumbar vertebra.

[0087] A transverse process pair refers to the transverse processes in the second and third transverse process images that belong to the same vertebra. For example, if transverse process A in the second transverse process image is the transverse process of the first vertebra, and transverse process B in the third transverse process object is also the transverse process of the first vertebra, then transverse processes A and B are in the same vertebra and are considered a transverse process pair.

[0088] Registration algorithms include, but are not limited to, point cloud registration algorithms. A registration matrix can be used to convert the 3D coordinate information in an ultrasound image into the 3D coordinate information in a medical image. The inverse of the registration matrix can be used to convert the 3D coordinate information in a medical image into the 3D coordinate information in an ultrasound image, thereby enabling fusion between ultrasound and medical images.

[0089] The three-dimensional reconstruction model corresponding to the medical image refers to a three-dimensional reconstruction model constructed using multiple frames of continuous medical images.

[0090] In some embodiments, the process of acquiring a 3D reconstructed model includes: performing data preprocessing on multiple frames of medical images to obtain preprocessed medical images; and performing 3D reconstruction on the preprocessed medical images using a 3D reconstruction algorithm to obtain a 3D reconstructed model. Data preprocessing includes at least one of denoising, image registration, and normalization. Denoising refers to reducing noise in medical images; normalization refers to adjusting the grayscale range in medical images; and image registration refers to aligning multiple frames of medical images to the same coordinate system. 3D reconstruction methods include, but are not limited to, voxel interpolation and surface reconstruction.

[0091] The cross-sectional image acquisition process includes converting the coordinates of the ultrasound image into transformed coordinates in the 3D reconstructed model based on the registration matrix, and determining the cross-sectional image of the ultrasound image in the 3D reconstructed model based on the transformed coordinates. Specifically, the image in the 3D reconstructed model where the transformed coordinates are located is determined as the cross-sectional image.

[0092] In some embodiments, the console can also fuse the cross-sectional image and the ultrasound image to obtain a fused image, so as to guide the puncture based on the fused image, the cross-sectional image, and the ultrasound image to improve the puncture accuracy.

[0093] Optionally, the console uses the trained segmentation model to segment the third transverse process image from the medical image of the vertebral part of the target object, and sorts the transverse processes in the third transverse process image according to the three-dimensional coordinate information of each transverse process in the third transverse process image, and obtains the vertebra where each transverse process in the third transverse process image is located according to the sorting result. The console determines the transverse processes of the second transverse process image and the third transverse process image in the same vertebra as a transverse process pair, and aligns the ultrasound image and the medical image according to the three-dimensional coordinate information of each transverse process in the transverse process pair to obtain a registration matrix. Based on the registration matrix, the console converts the coordinates of the ultrasound image into conversion coordinates in the three-dimensional reconstruction model. The console searches for the cross-sectional image corresponding to the conversion coordinates in the three-dimensional reconstruction model. The console performs puncture guidance based on the cross-sectional image and the ultrasound image.

[0094] In this embodiment, the ultrasound image and the medical image are registered according to the three-dimensional coordinate information of each transverse process in the transverse process pair to obtain a registration matrix. Based on the registration matrix, the cross-sectional image of the ultrasound image in the three-dimensional reconstructed model corresponding to the medical image is determined. In this way, high-precision spatial alignment can be achieved based on the coordinate information of multiple transverse processes, and the registration error can be reduced, making the registration matrix more accurate. Therefore, in scenarios such as puncture, the puncture can be correctly guided by the ultrasound image and the cross-sectional image determined based on the registration matrix.

[0095] This application also provides an application scenario, which applies the above-mentioned transverse process positioning method. Specifically, the application of the transverse process positioning method in this application scenario is as follows: The console segments a first transverse process image of multiple transverse processes from an ultrasound image of the vertebrae of the target subject using one or more segmentation methods. The console binarizes the segmented first transverse process image to produce a binary image. The console identifies the edge contours of each transverse process in the binary image and determines the center of mass of the edge contours by averaging the coordinates of all points within the edge contours. The console determines the center of mass of the edge contours as the center of the transverse process of the target subject's vertebrae, or determines a circumscribed figure containing the edge contours and determines the center of the circumscribed figure as the center of the transverse process of the target subject's vertebrae.

[0096] The console uses an ultrasound probe to scan the center of each transverse process of the target object from multiple directions, obtaining the two-dimensional coordinates of each transverse process center in each direction. The console then obtains a transformation matrix from the ultrasound plane to electromagnetic space and uses the transformation matrix to convert the two-dimensional coordinates of each transverse process center in each direction into a first coordinate in electromagnetic space.

[0097] The console builds a data matrix based on multiple first coordinates X , calculate the mean value of each column in the data matrix and get the mean vector , calculate the data matrix X Subtract the mean vector The difference between X c The console calculates the covariance matrix of the centralization matrix and decomposes the covariance matrix through singular value decomposition C , and get the covariance matrix C The eigenvalues ​​and eigenvectors corresponding to each eigenvalue. The console uses the eigenvector corresponding to the maximum eigenvalue as the projection axis. V 1. Project each first coordinate onto the projection axis V 1. Get the third coordinate after projection of each first coordinate The console is based on each third coordinate X p Perform cluster analysis to obtain cluster centers. The console sorts the cluster centers from low to high according to their coordinate values ​​on the projection axis to obtain the sorting results of the cluster centers, and then determines the vertebrae corresponding to the cluster centers based on the sorting results.

[0098] The console segments a second transverse process image of multiple transverse processes from an ultrasound image of the vertebral region of the target subject. The console determines the two-dimensional coordinates of each transverse process in the second transverse process image and converts the two-dimensional coordinates into second coordinates in electromagnetic space. The console performs centralization processing on the second coordinates to obtain a centralized second coordinate. The console projects the centralized second coordinates onto the projection principal axis to obtain a fourth coordinate of each projected transverse process. The console calculates the distance between each fourth coordinate and each cluster center and, based on the calculation results, determines the target center closest to each transverse process from the cluster center.

[0099] The console identifies the vertebra corresponding to each target center as the vertebra where the transverse process is located. Using the trained segmentation model, the console segments the third transverse process image from the medical image of the target object's vertebrae. Based on the three-dimensional coordinate information of each transverse process in the third transverse process image, the console sorts the transverse processes in the third transverse process image. Based on the sorting result, the console determines the transverse processes in the second and third transverse process images of the same vertebra as a transverse process pair. Based on the three-dimensional coordinate information of each transverse process in the transverse process pair, the console registers the ultrasound image and the medical image to obtain a registration matrix. Based on the registration matrix, the console converts the coordinates of the ultrasound image into transformed coordinates in the three-dimensional reconstructed model. The console searches for the cross-sectional image corresponding to the transformed coordinates in the three-dimensional reconstructed model. The console performs puncture guidance based on the cross-sectional image and the ultrasound image.

[0100] It should be understood that, although the various steps in the flowcharts involved in the various embodiments described above are displayed in sequence according to the instructions of the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowcharts involved in the various embodiments described above can include multiple steps or multiple stages, and these steps or stages are not necessarily executed and completed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0101] Based on the same inventive concept, embodiments of the present application also provide a transverse process positioning device for implementing the aforementioned transverse process positioning method. The solution provided by this device is similar to the solution described in the aforementioned method. Therefore, the specific limitations of one or more transverse process positioning device embodiments provided below can be found in the aforementioned limitations of the transverse process positioning method and will not be further elaborated here.

[0102] In one embodiment, Figure 4 As shown, a transverse process positioning device is provided, comprising: The scanning module 402 is configured to scan the transverse process centers of the target object from multiple directions to obtain the first coordinates of each transverse process center in each direction.

[0103] The analysis module 404 is configured to perform principal component analysis and cluster analysis based on the first coordinates to obtain the cluster center of each vertebra.

[0104] The center determination module 406 is used to determine the target center closest to the transverse process from the cluster centers based on the second coordinates of each transverse process in the ultrasound image of the target object and the coordinates of the cluster centers; the first coordinate and the second coordinate are both three-dimensional coordinates.

[0105] The positioning module 408 is configured to determine the vertebra corresponding to the target center as the vertebra where the transverse process is located.

[0106] In one embodiment, the transverse process positioning device is also used to: determine the transverse process center of the target object; use an ultrasonic probe to scan each transverse process center from multiple directions to obtain the two-dimensional coordinates of each transverse process center in each direction; and convert the two-dimensional coordinates of each transverse process center in each direction into a first coordinate in the electromagnetic space.

[0107] In one embodiment, the transverse process positioning device is further used to: segment a first transverse process image of multiple transverse processes from an ultrasound image of a vertebral portion of a target object; binarize the first transverse process image to obtain a binarized image, and identify the edge contours of each transverse process in the binarized image; determine the centroid of the edge contour as the transverse process center of the target object vertebra, or determine a circumscribed figure containing the edge contour, and determine the center of the circumscribed figure as the transverse process center of the target object vertebra.

[0108] In one embodiment, the transverse process positioning device is also used to: construct a data matrix based on each first coordinate, and centralize the data matrix to obtain a centralized matrix; calculate the covariance matrix of the centralized matrix, and calculate the eigenvalues ​​of the covariance matrix and the eigenvectors corresponding to the eigenvalues; use the eigenvector corresponding to the maximum eigenvalue as the projection axis, project each first coordinate onto the projection axis, and obtain the third coordinate after each first coordinate is projected; perform cluster analysis based on each third coordinate to obtain the cluster center of each vertebra.

[0109] In one embodiment, the transverse process positioning device is further used to: sort the cluster centers according to the coordinate sizes of the cluster centers on the projection axis; and determine the vertebrae corresponding to the cluster centers according to the sorting results of the cluster centers.

[0110] In one embodiment, the transverse process positioning device is also used to: segment a second transverse process image of multiple transverse processes from an ultrasound image of the vertebral part of the target object; determine the two-dimensional coordinates of each transverse process in the second transverse process image, and convert the two-dimensional coordinates into a second coordinate in the electromagnetic space; center the second coordinate to obtain a centralized second coordinate; project the centralized second coordinate onto the projection main axis to obtain a fourth coordinate of each transverse process after projection; and based on each fourth coordinate, determine the target center closest to each transverse process from the cluster center.

[0111] In one embodiment, the transverse process positioning device is also used to: segment the third transverse process image from the medical image of the vertebral part of the target object, and determine the vertebrae where each transverse process in the third transverse process image is located; determine the transverse processes in the second transverse process image and the third transverse process image in the same vertebra as a transverse process pair; align the ultrasound image and the medical image according to the three-dimensional coordinate information of each transverse process in the transverse process pair to obtain a registration matrix; based on the registration matrix, determine the cross-sectional image of the ultrasound image in the three-dimensional reconstructed model corresponding to the medical image, so as to perform puncture guidance based on the cross-sectional image and the ultrasound image.

[0112] Each module in the transverse process positioning device can be implemented in whole or in part through software, hardware, or a combination thereof. Each module can be embedded in or independent of a processor in a computer device in the form of hardware, or can be stored in a memory in the computer device in the form of software, so that the processor can call and execute the corresponding operations of each module.

[0113] In one embodiment, a computer device is provided. The computer device may be a server, and its internal structure diagram may be as follows: Figure 5 As shown. The computer device includes a processor, a memory and a network interface connected through a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store the first coordinate, the cluster center, the second coordinate, the target center, and the vertebra where the transverse process is located. The network interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a transverse process positioning method is implemented.

[0114] Those skilled in the art will understand that Figure 5 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement.

[0115] In one embodiment, a computer device is further provided, including a memory and a processor. The memory stores a computer program, and the processor implements the steps in the above method embodiments when executing the computer program.

[0116] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps in the above-mentioned method embodiments are implemented.

[0117] In one embodiment, a computer program product is provided, including a computer program, which implements the steps in the above method embodiments when executed by a processor.

[0118] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0119] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the above-mentioned embodiments. In particular, any reference to memory, database, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The databases involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processors involved in the various embodiments provided herein may be, but are not limited to, general-purpose processors, central processing units (CPUs), graphics processing units (GPUs), digital signal processors (DSPs), programmable logic devices (PLDs), data processing logic devices based on quantum computing, and the like.

[0120] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, 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.

[0121] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A transverse process positioning method, characterized in that: The method comprises: Scanning the transverse process center of the target object from multiple directions to obtain a first coordinate of each transverse process center in each direction; Performing principal component analysis and cluster analysis based on each of the first coordinates to obtain a cluster center for each vertebra; determining, from the cluster centers, a target center closest to the transverse process according to the second coordinates of each transverse process in the ultrasound image of the target object and the coordinates of the cluster centers, wherein both the first coordinates and the second coordinates are three-dimensional coordinates; The vertebra corresponding to the target center is determined as the vertebra where the transverse process is located.

2. The method according to claim 1, characterized in that Scanning the transverse process center of the target object from multiple directions to obtain the first coordinate of each transverse process center in each direction includes: Determine the transverse process center of the target object; Scanning the center of each transverse process from multiple directions using an ultrasonic probe to obtain the two-dimensional coordinates of the center of each transverse process in each direction; The two-dimensional coordinates of the center of each transverse process in each direction are converted into first coordinates in the electromagnetic space.

3. The method according to claim 2, characterized in that Determining the center of the transverse process of each vertebra of the target object includes: Segmenting a first transverse process image of a plurality of transverse processes from an ultrasound image of a vertebral region of the target object; Binarizing the first transverse process image to obtain a binary image, and identifying the edge contour of each transverse process in the binary image; The centroid of the edge contour is determined as the center of the transverse process of the target vertebra, or a circumscribed figure containing the edge contour is determined, and the center of the circumscribed figure is determined as the center of the transverse process of the target vertebra.

4. The method according to claim 1, wherein The performing principal component analysis and cluster analysis based on each of the first coordinates to obtain the cluster center of each vertebra includes: constructing a data matrix based on each of the first coordinates, and performing centralization processing on the data matrix to obtain a centralized matrix; Calculating a covariance matrix of the centralization matrix, and calculating eigenvalues ​​of the covariance matrix and eigenvectors corresponding to the eigenvalues; Taking the eigenvector corresponding to the maximum eigenvalue as the projection axis, projecting each of the first coordinates onto the projection axis to obtain a third coordinate after each of the first coordinates is projected; Cluster analysis is performed based on each of the third coordinates to obtain a cluster center of each vertebra.

5. The method according to claim 4, characterized in that The method further comprises: Sort the cluster centers according to their coordinate sizes on the projection axis; According to the ranking results of the cluster centers, the vertebrae corresponding to the cluster centers are determined.

6. The method according to claim 4, characterized in that Determining, from the cluster centers, a target center closest to the transverse process based on the second coordinates of each transverse process in the ultrasound image of the target object and the coordinates of the cluster centers, includes: a second transverse process image segmenting a plurality of transverse processes from an ultrasound image of a vertebral region of the target subject; determining the two-dimensional coordinates of each transverse process in the second transverse process image, and converting the two-dimensional coordinates into second coordinates in electromagnetic space; performing centralization processing on the second coordinate to obtain a centralized second coordinate; Projecting the centralized second coordinate onto the projection principal axis to obtain the fourth coordinate of each transverse process after projection; Based on each of the fourth coordinates, a target center closest to each of the transverse processes is determined from the cluster centers.

7. The method according to claim 6, characterized in that The method further comprises: Segmenting a third transverse process image from a medical image of the vertebral portion of the target subject, and determining the vertebra where each transverse process in the third transverse process image is located; determining the transverse processes of the same vertebra in the second transverse process image and the third transverse process image as a transverse process pair; registering the ultrasound image and the medical image according to the three-dimensional coordinate information of each transverse process in the transverse process pair to obtain a registration matrix; Based on the registration matrix, a cross-sectional image of the ultrasound image in the three-dimensional reconstructed model corresponding to the medical image is determined, so as to perform puncture guidance based on the cross-sectional image and the ultrasound image.

8. A transverse process positioning device, characterized in that: The device comprises: A scanning module, configured to scan the transverse process center of the target object from multiple directions to obtain a first coordinate of each transverse process center in each direction; an analysis module, configured to perform principal component analysis and cluster analysis based on each of the first coordinates to obtain a cluster center of each vertebra; a center determination module, configured to determine, from the cluster centers, a target center closest to the transverse process based on the second coordinates of each transverse process in the ultrasound image of the target object and the coordinates of the cluster centers; wherein both the first coordinates and the second coordinates are three-dimensional coordinates; A positioning module is used to determine the vertebra corresponding to the target center as the vertebra where the transverse process is located.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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