Respiratory Phase Search Method and Device Based on Electromagnetic Tracking

Abstract

A respiratory phase search method and device based on electromagnetic tracking involves attaching magnetic positioning tags to the patient before surgery and taking preoperative images. During surgery, magnetic sensors are installed on the magnetic positioning tags for calibration, and a transformation matrix of the magnetic positioning tags is obtained. The transformation matrix is ​​used to record the position information of multiple respiratory cycle markers of the patient during surgery. The position information of multiple respiratory cycle markers is repeatedly registered with the position information of markers in the preoperative images to search for the respiratory phase that matches the respiratory phase of the preoperative images. Electromagnetic positioning tracking has the characteristics of fast response and high accuracy, which can accurately reflect the patient's respiratory phase in real time. Electromagnetic positioning tracking can avoid the problem of obstructed vision. The electromagnetic positioning tags can be changed according to the surgical procedure to better capture local respiratory phase changes of the patient.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electromagnetic tracking, and in particular to a respiratory phase searching method based on electromagnetic tracking and a respiratory phase searching device based on electromagnetic tracking. BACKGROUND

[0002] Respiratory motion is a kind of periodic physiological activity, and respiratory phase can be regarded as an expression of such motion, which is used to reflect the position of the target in the respiratory motion cycle. Respiratory phase has a one-to-one mapping relationship with the target respiratory motion. At present, respiratory phase searching is performed by technologies such as a respiratory bellows, optical tracking, electromagnetic tracking, fluoroscopy images, and image internal feature points.

[0003] Electromagnetic tracking technology constructs a space magnetic field through an electromagnetic field generator, and an electromagnetic receiver receives magnetic field signals in the space magnetic field in accordance with the electromagnetic induction law, and solves the current pose information of the electromagnetic receiver by using a conversion relationship. Electromagnetic positioning and tracking is a tracking technology with the advantages of high precision, high response frequency, simple operation, and no occlusion problem, and can be used to accurately reflect the respiratory phase of a patient in real time during surgery.

[0004] A surgical navigation system needs to plan target points, surgical paths and other operations according to preoperative images of a patient, so as to guide and position in surgery according to the planning in the preoperative images. It is particularly important for the positioning accuracy of the surgical navigation system to accurately search the respiratory phase of the patient when the preoperative images are taken during surgery. Since the respiratory phase of the patient during surgery cannot be guaranteed to be the same as the respiratory phase of the patient when the preoperative CT images are taken, the target points planned according to the preoperative images will deviate during positioning in surgery. In order to find the same respiratory phase when the preoperative images are taken, it is necessary to search the respiratory phase during surgery.

[0005] By integrating electromagnetic tracking into the surgical navigation system, the surgical navigation system can accurately obtain the respiratory phase of the patient in real time during surgery. By searching the respiratory phase of the patient when the image data is taken, the positioning error caused by the inconsistency of the preoperative respiratory phase during surgery can be avoided. SUMMARY

[0006] To overcome the defects of the prior art, the present application solves the technical problem of providing a respiratory phase searching method based on electromagnetic tracking, which can solve the technical problem of errors caused by the inconsistency of the respiratory phase of the patient during surgery and the respiratory phase of the patient when the preoperative images are taken, and can search the respiratory phase of the patient when the preoperative images are taken during surgery.

[0007] The technical scheme of the present application is: the respiratory phase searching method based on electromagnetic tracking, which comprises the following steps:

[0008] (1) Preoperative patient pastes magnetic positioning mark to shoot preoperative image, the magnetic positioning mark is provided with mark points, the mark points are arranged in a certain geometric structure, multiple magnetic positioning marks are pasted near the operation range of the patient to shoot the image, the position relationship of the mark points in the image coordinate system in the preoperative image data is obtained, and the position relationship is recorded as the respiratory phase of the patient shooting the preoperative image;

[0009] (2) Intraoperative calibration of the magnetic sensor installed on the magnetic positioning mark to obtain the magnetic positioning mark conversion matrix, which represents the spatial position conversion relationship from the magnetic sensor to the mark points of the magnetic positioning mark;

[0010] (3) Recording the position information of multiple respiratory cycle mark points of the patient during the operation by using the magnetic positioning mark conversion matrix;

[0011] (4) Multiple intraoperative registrations are performed by using the position information of the multiple respiratory cycle mark points and the position information of the mark points in the preoperative image to search for the respiratory phase matching the respiratory phase of the preoperative image.

[0012] The present application pastes the magnetic positioning mark on the preoperative patient to shoot the preoperative image, calibrates the magnetic sensor installed on the magnetic positioning mark during the operation to obtain the magnetic positioning mark conversion matrix, records the position information of multiple respiratory cycle mark points of the patient during the operation by using the magnetic positioning mark conversion matrix, performs multiple registrations by using the position information of the multiple respiratory cycle mark points and the position information of the mark points in the preoperative image, and searches for the respiratory phase matching the respiratory phase of the preoperative image. The electromagnetic positioning tracking has the characteristics of high speed and high accuracy, can accurately reflect the respiratory phase of the patient in real time, can avoid the problem of occluded line of sight, and can better obtain the local respiratory phase change of the patient according to the operation type. Therefore, the technical problem of errors in intraoperative navigation and preoperative planning caused by the inconsistency between the respiratory phase of the patient during the operation and the respiratory phase of the patient shooting the preoperative image can be solved, and the respiratory phase of the patient shooting the preoperative image can be searched during the operation.

[0013] A respiratory phase searching device based on electromagnetic tracking is also provided, which comprises:

[0014] A position relationship obtaining module configured to perform: preoperative patient pastes magnetic positioning mark to shoot preoperative image, the magnetic positioning mark is provided with mark points, the mark points are arranged in a certain geometric structure, multiple magnetic positioning marks are pasted near the operation range of the patient to shoot the image, the position relationship of the mark points in the image coordinate system in the preoperative image data is obtained, and the position relationship is recorded as the respiratory phase of the patient shooting the preoperative image;

[0015] a conversion matrix module configured to perform: in-vivo calibration of the magnetic positioning marker sticker with the magnetic sensor, and obtain a conversion matrix of the magnetic positioning marker sticker, the conversion matrix representing a spatial position conversion relationship from the magnetic sensor to the marker points of the magnetic positioning marker sticker;

[0016] a position information recording module configured to perform: recording of position information of a plurality of respiratory cycle marker points of the patient in-vivo using the conversion matrix of the magnetic positioning marker sticker;

[0017] a registration search module configured to perform: multiple in-vivo registrations of the position information of the plurality of respiratory cycle marker points with the position information of the marker points in the preoperative image, and search for a respiratory phase matching the respiratory phase of the preoperative image. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a flowchart of the electromagnetic tracking-based respiratory phase search method according to the present application.

[0019] Figure 2 is a flowchart of the calibration of the magnetic positioning marker sticker according to the present application.

[0020] Figure 3 is a flowchart of the CT image marker point detection module according to the present application.

[0021] Figure 4 is a flowchart of the respiratory phase search module according to the present application. DETAILED DESCRIPTION

[0022] As shown in Figure 1 , the electromagnetic tracking-based respiratory phase search method includes the following steps:

[0023] (1) Preoperative patient pastes the magnetic positioning marker sticker to shoot the preoperative image, the magnetic positioning marker sticker has marker points, the marker points are arranged in a certain geometric structure, a plurality of magnetic positioning marker stickers are pasted near the patient operation range to shoot the image, the position relationship of the marker points in the image coordinate system in the preoperative image data is obtained, and the position relationship is recorded as the respiratory phase of the patient shooting the preoperative image;

[0024] (2) In-vivo calibration of the magnetic positioning marker sticker with the magnetic sensor, and obtain a conversion matrix of the magnetic positioning marker sticker, the conversion matrix representing a spatial position conversion relationship from the magnetic sensor to the marker points of the magnetic positioning marker sticker;

[0025] (3) Recording of position information of a plurality of respiratory cycle marker points of the patient in-vivo using the conversion matrix of the magnetic positioning marker sticker;

[0026] (4) Multiple in-vivo registrations of the position information of the plurality of respiratory cycle marker points with the position information of the marker points in the preoperative image, and search for a respiratory phase matching the respiratory phase of the preoperative image.

[0027] The present application pastes the magnetic positioning mark sticker to shoot the preoperative image, calibrates the magnetic positioning mark sticker installed with the magnetic sensor in the operation, obtains the conversion matrix of the magnetic positioning mark sticker, records the position information of the multiple breathing cycle mark points of the patient in the operation by using the conversion matrix of the magnetic positioning mark sticker, performs multiple registrations by using the position information of the multiple breathing cycle mark points and the position information of the mark points in the preoperative image, searches out the breathing phase matched with the breathing phase of the preoperative image, and uses the electromagnetic positioning tracking which has the characteristics of high speed and high accuracy, can accurately reflect the breathing phase of the patient in real time, and can avoid the problem of occlusion of the line of sight. The electromagnetic positioning mark sticker can be changed according to the operation type, and better obtain the local breathing phase change of the patient. Therefore, the technical problem that the error is caused between the intraoperative navigation and the preoperative planning due to the fact that the breathing phase of the patient in the operation does not match the breathing phase of the patient when the preoperative image is shot can be solved, and the breathing phase of the patient when the preoperative image is shot can be searched out in the operation.

[0028] Preferably, in the step (4), the intraoperative registration is to calculate the conversion matrix from the image coordinate system to the magnetic field generator coordinate system by using the position of the mark point of the magnetic positioning mark sticker in the image coordinate system and the position of the mark point of the magnetic positioning mark sticker in the magnetic field generator coordinate system; the registration process is accompanied by the breathing cycle of the patient, multiple registrations are performed to obtain multiple conversion matrices, and the position information of the magnetic sensor for obtaining each conversion matrix is recorded; the conversion matrix with the minimum registration error is selected as the conversion matrix from the image coordinate system to the magnetic field generator coordinate system, and the position coordinate information of the magnetic sensor at this time is obtained, and the position information of the magnetic sensor at this time is used as the searched breathing phase matched with the breathing phase of the patient when the preoperative image is shot.

[0029] Preferably, after the step (4) is completed, the position relationship of the magnetic positioning sensor is recorded at all times, the Euclidean distance between each sensor at each time and the sensor in the searched breathing phase is calculated, and if the distance is less than a preset value, it is represented that the breathing phase of the patient reaches the breathing phase when the preoperative image is shot, and the breathing phase of the patient when the preoperative image is shot is searched out in the operation.

[0030] Preferably, as shown in the step (1), the step (1) comprises the following steps: Figure 2

[0031] (1.1) the magnetic positioning mark sticker is installed with the magnetic positioning sensor;

[0032] (1.2) the positions of the mark points in the coordinate system of the mark sticker are sequentially obtained in order

[0033] P M {p1,p2,p3,p4}, wherein p i The coordinate values p of the mark points in the coordinate system of the mark sticker are recorded​i = {x, y, z};

[0034] (1.3) Obtain the position P of the marker point in the magnetic positioning sensor coordinate system in sequence according to the order E {p1, p2, p3, p4}, wherein p i Record the coordinate value p of the marker point in the magnetic positioning sensor coordinate system i = {x, y, z};

[0035] (1.4) Calculate the conversion matrix of the magnetic positioning marker coordinate system to the magnetic positioning sensor coordinate system, list the equation group P M X = P E , solve X, and set the conversion matrix

[0036] Preferably, as shown in the step (3) comprises the following steps: Figure 3

[0037] (3.1) Set the CT image data as I(y), wherein y = (x T ,v) T ∈R 3 ×R, y represents a coordinate I on a CT image, including a spatial position x ∈ R 3 and a brightness value v ∈ R at the position, each coordinate point has its corresponding brightness value, and the CT data I(y) is imported;

[0038] (3.2) Set a brightness threshold value v1 = 2000, then obtain all points y with brightness equal to 2000 in I(y), obtain a candidate point set I1(y), and the coordinate points with brightness not equal to 2000 are discarded;

[0039] (3.3) If the number of y in the candidate point set I1(y) is not equal to the number of marker points y, adjust the brightness threshold value to obtain a brightness threshold value v2, and screen y in the point set I1(y) to obtain a candidate point set I2(y); after adjusting the brightness threshold value for multiple times, when the number of points y in the candidate point set is equal to the number of marker points, a final point set I M (y) is obtained.

[0040] Preferably, as shown in the step (4) comprises the following steps: Figure 4

[0041] (4.1) Install a magnetic positioning sensor on the magnetic positioning marker of the patient during the operation;

[0042] (4.2) Obtain a plurality of respiratory phase position sets S = {s1, s2, s3,..., s n} of the magnetic positioning sensor under a respiratory cycle of the patient, wherein s = {x, y, z} is the sensor position coordinate;​​

[0043] (4.3) Using the transformation matrix Solving the coordinate positions of the magnetic positioning marker points under multiple breathing phases Obtaining the magnetic positioning marker point set S m ;

[0044] (4.4) Using the magnetic positioning marker point set S m and the marker point set I in the CT image M (y), I M (y) = S m X solving X to obtain the transformation matrix from the coordinate system of the magnetic positioning marker to the CT image set, t n representing the transformation matrix obtained under different breathing phases;

[0045] (4.5) Verification of the transformation accuracy of each transformation matrix, and setting the accuracy requirement to be

[0046] 1mm, then pass wherein i∈(1, n), q = (l), l = {x, y, z}, q is the coordinate value of the sensor coordinate converted to the marker point in the CT image using the transformation matrix; and the Euclidean distance of q i

[0047] to I M (y) is calculated, and if the distance satisfies the Euclidean distance, it is considered that t i the transformation matrix under the breathing phase matches the breathing phase of the patient when the CT image is taken, and if it does not satisfy, the Euclidean distance of the next breathing phase is calculated.

[0048] Those skilled in the art can understand that all or part of the steps in the above-mentioned embodiment method can be completed by programs instructing related hardware, and the programs can be stored in a computer readable storage medium. When the program is executed, each step of the above-mentioned embodiment method is included, and the storage medium can be ROM / RAM, a magnetic disc, an optical disc, a memory card, etc. Therefore, corresponding to the method of the present application, the present application also simultaneously includes a breathing phase searching device based on electromagnetic tracking. The device is usually represented in the form of a functional module corresponding to each step of the method. The device includes:

[0049] The position relationship obtaining module is configured to perform: pasting magnetic positioning mark stickers on a patient to shoot preoperative images, the magnetic positioning mark stickers are provided with mark points, the mark points are arranged in a certain geometric structure, multiple magnetic positioning mark stickers are pasted near a surgery range of the patient to shoot images, position relationships of the mark points in an image coordinate system in preoperative image data are obtained, and a breathing phase of shooting the preoperative images of the patient is recorded according to the position relationships;

[0050] The conversion matrix module is configured to perform: in-surgery calibration of the magnetic positioning mark stickers provided with magnetic sensors to obtain magnetic positioning mark sticker conversion matrices, the magnetic positioning mark sticker conversion matrices represent a spatial position conversion relationship from the magnetic sensors to the mark points of the magnetic positioning mark stickers;

[0051] The position information recording module is configured to perform: recording position information of multiple breathing cycle mark points of the patient in-surgery by using the magnetic positioning mark sticker conversion matrices;

[0052] The registration searching module is configured to perform: multiple in-surgery registrations by using the position information of the multiple breathing cycle mark points and the position information of the mark points in the preoperative images to search for a breathing phase matching the breathing phase of the preoperative images.

[0053] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification, equivalent change and modification made according to the technical essence of the present application to the above embodiment are still within the protection scope of the technical solution of the present application.

Claims

1. A method of respiratory phase searching based on electromagnetic tracking, characterized in that: It comprises the following steps: (1) Preoperative patient pastes magnetic positioning mark sticker to shoot preoperative image, the magnetic positioning mark sticker is provided with mark points, the mark points are arranged in a certain geometric structure, multiple magnetic positioning mark stickers are pasted near the operation range of the patient to shoot the image, the position relationship of the mark points in the image coordinate system in the preoperative image data is obtained, and the position relationship is recorded as the respiratory phase of the patient shooting the preoperative image; (2) Intraoperative calibration of the magnetic positioning mark sticker installed with the magnetic sensor obtains the magnetic positioning mark sticker conversion matrix, and the magnetic positioning mark sticker conversion matrix represents the spatial position conversion relationship from the magnetic sensor to the mark points of the magnetic positioning mark sticker; (3) The position information of multiple respiratory cycle mark points of the patient during the operation is recorded by using the magnetic positioning mark sticker conversion matrix; (4) Multiple intraoperative registrations are performed by using the position information of multiple respiratory cycle mark points and the position information of mark points in the preoperative image, and the respiratory phase matching the respiratory phase of the preoperative image is searched out; In the step (4), the intraoperative registration is to calculate the conversion matrix from the image coordinate system to the magnetic field generator coordinate system by using the position of the mark points of the magnetic positioning mark sticker in the image coordinate system and the position of the mark points of the magnetic positioning mark sticker in the magnetic field generator coordinate system; The registration process is accompanied by the respiratory cycle of the patient, multiple registrations are performed to obtain multiple conversion matrices, and the position information of the magnetic sensor obtaining each conversion matrix is recorded; The conversion matrix with the minimum registration error is selected as the conversion matrix from the image coordinate system to the magnetic field generator coordinate system, and the position coordinate information of the magnetic sensor at this time is obtained, and the position information of the magnetic sensor at this time is used as the respiratory phase matching the respiratory phase of the preoperative patient shooting image; After the step (4) completes the intraoperative registration, the position relationship of the magnetic positioning sensor is recorded at any time, and the Euclidean distance between each sensor at each time and the sensor in the searched respiratory phase is calculated, if the distance is less than a preset value, it means that the respiratory phase of the patient reaches the respiratory phase of the preoperative shooting, and the respiratory phase of the patient shooting the preoperative image is searched in the operation.

2. The electromagnetic tracking-based respiratory phase search method of claim 1, wherein: The step (1) comprises the following steps: (1.1) Magnetic positioning mark sticker installs magnetic positioning sensor; (1.2) The positions of the mark points in the mark sticker coordinate system are obtained in sequence P M {p1,p2,p3,p4}, where p i The coordinate values of the marker points in the marker sticker coordinate system are recorded as p i = {x, y, z}; (1.3) sequentially acquiring the position P of the marker point in the coordinate system of the magnetic positioning sensor according to the order E {p1,p2,p3,p4}, wherein p i The coordinate value p of the marker point in the coordinate system of the magnetic positioning sensor is recorded i = {x, y, z}; (1.4) Calculate the conversion matrix of the magnetic positioning marker coordinate system to the magnetic positioning sensor coordinate system, list the equation group P M X = P E , solve X, set the conversion matrix 3. The electromagnetic tracking-based respiratory phase search method of claim 2, wherein: The step (3) comprises the following steps: (3.1) Let CT image data be denoted as I(y), where y = (x T ,v) T ∈R 3 ×R, y represents a coordinate of I on a CT image, including spatial position x ∈ R 3 and brightness value v ∈ R at the position, each coordinate point has its corresponding brightness value, and the CT data I(y) is imported; (3.2) Set a brightness threshold value v1=2000, then obtain all points y with brightness equal to 2000 in I(y), obtain the candidate point set I1(y), and discard the coordinate points with brightness not equal to 2000; (3.3) If the number of y in the candidate point set I1(y) is not equal to the number of marked points y, adjust the brightness threshold value to obtain the brightness threshold value v2, and screen y in the point set I1(y) to obtain the candidate point set I2(y); after adjusting the brightness threshold value for many times, when the number of points y in the candidate point set is equal to the number of marked points, the final point set I M (y) is obtained.

4. The electromagnetic tracking-based respiratory phase search method of claim 3, wherein: The step (4) comprises the following steps: (4.1) The magnetic positioning mark sticker of the patient during the operation is installed with the magnetic positioning sensor; (4.2) Obtain a set of magnetic positioning sensor positions at multiple respiratory phases under one respiratory cycle of the patient, S = {s1, s2, s3,... s n}, where s = {x, y, z} is the sensor position coordinates; (4.3) using a transformation matrix Solving for coordinate positions of magnetic localization marker points at multiple respiratory phases Obtaining a set S of magnetic localization marker points m ; (4.4) Using the magnetic localization landmark point set S m with the CT image landmark point set I M (y), I M (y) = S m X to obtain the conversion matrix from the magnetic localization landmark coordinate system to the CT image set, representing the conversion matrices obtained at different respiratory phases; (4.5) verification The conversion accuracy of each conversion matrix is set to 1 mm, and the conversion accuracy of each conversion matrix is set to 1 mm. Wherein i∈(1,n), q=(l), l={x,y,z}, q is the coordinate value of the landmark point in the CT image obtained by converting the sensor coordinate using the conversion matrix; calculate q i To I M The Euclidean distance of (y) is calculated, and if the distance satisfies the Euclidean distance, it is considered that t i The conversion matrix under the respiratory phase matches the respiratory phase of the patient when the CT image is taken, and if it does not satisfy, the Euclidean distance of the next respiratory phase is calculated.

5. The electromagnetic tracking-based respiratory phase searching method device of claim 1, wherein: It comprises: A position relationship acquisition module configured to perform: preoperative patient pastes magnetic positioning mark sticker to shoot preoperative image, the magnetic positioning mark sticker is provided with mark points, the mark points are arranged in a certain geometric structure, multiple magnetic positioning mark stickers are pasted near the operation range of the patient to shoot the image, the position relationship of the mark points in the image coordinate system in the preoperative image data is obtained, and the position relationship is recorded as the respiratory phase of the patient shooting the preoperative image; The conversion matrix module is configured to perform: in-vivo calibration of the magnetic positioning marker sticker with the magnetic sensor, and obtaining a magnetic positioning marker sticker conversion matrix, which represents a spatial position conversion relationship from the magnetic sensor to the magnetic positioning marker sticker marker point; The position information recording module is configured to perform: recording position information of a plurality of breathing cycle marker points of the patient in-vivo by using the magnetic positioning marker sticker conversion matrix; The registration search module is configured to perform: multiple in-vivo registrations by using the position information of the plurality of breathing cycle marker points and the position information of the marker points in the preoperative image, and searching for a breathing phase of the preoperative image that matches the breathing phase.

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