Motion tracking method and system suitable for medical imaging scanning

Abstract

The invention relates to a motion tracking method and system suitable for medical imaging scanning. The method comprises the steps that in the medical imaging scanning process, the camera is used for obtaining an optical image of the marker; the marker is irradiated by the light source; determining a rotation angle of the marker based on the optical image; the rotation angle comprises at least one of an in-plane rotation angle and an out-of-plane rotation angle; and obtaining motion information of the detection object according to the rotation angle. By adopting the method, the precision of motion tracking can be improved.

Description

Technical Field

[0001] The present application relates to the field of medical image processing technology, and in particular to a motion tracking method and system suitable for medical imaging scanning. Background Art

[0002] Magnetic resonance imaging (MRI) is a crucial diagnostic tool in modern medicine, capable of high-resolution imaging of soft tissues such as the brain and blood vessels. However, since scanning times are typically long, patients inevitably move during MRI, resulting in motion artifacts in the resulting MRI images. Therefore, motion tracking is required during the imaging process, and motion artifacts in the MRI images are corrected based on the results of motion tracking.

[0003] In traditional technology, optical tracking methods are usually used to track motion using checkerboards and benchmark markers such as ArUco (augmented reality library), ARTag (augmented reality tag), and AprilTag (visual reference system). Although optical tracking methods can achieve high-precision measurement in the three translational degrees of freedom of an object, the measurement accuracy in the three rotational degrees of freedom of the object is not high.

[0004] Therefore, the current motion tracking technology has the problem of low accuracy. Summary of the Invention

[0005] Based on this, it is necessary to provide a motion tracking method, system, device, computer equipment, computer-readable storage medium and computer program product with higher precision to address the above technical problems.

[0006] In a first aspect, the present application provides a motion tracking method suitable for medical imaging scanning. A medical scanning device performing medical imaging scanning includes a scanner, a camera, and a light source. The scanner has a scanning cavity, and a detection object is accommodated in the scanning cavity. The detection object is provided with a marker including moiré patterns and feature points. The method includes:

[0007] During the medical imaging scan, the camera is used to obtain an optical image of the marker; the marker is illuminated by the light source;

[0008] Determining a rotation angle of the marker based on the optical image; the rotation angle includes at least one of an in-plane rotation angle and an out-of-plane rotation angle;

[0009] According to the rotation angle, motion information of the detection object is obtained.

[0010] In one embodiment, the motion information includes six-degree-of-freedom pose information; and determining the rotation angle of the marker based on the optical image includes:

[0011] Obtaining initial position information of the marker according to the feature point image in the optical image; the initial position information includes the in-plane rotation angle, the first out-of-plane rotation angle and translation information;

[0012] determining a second out-of-plane rotation angle of the marker according to a moiré pattern image in the optical image;

[0013] The second out-of-plane rotation angle is merged with the first out-of-plane rotation angle to obtain the out-of-plane rotation angle of the marker; the target posture information of the marker includes the in-plane rotation angle, the out-of-plane rotation angle and the translation information.

[0014] In one embodiment, determining the second out-of-plane rotation angle of the marker according to the moiré pattern image in the optical image includes:

[0015] determining, according to a preset moiré spatial frequency, an incident light offset corresponding to a moiré phase shift of the moiré image; the incident light offset comprising an offset of the incident light between a front surface and a rear surface of the marker;

[0016] The incident light offset is transformed according to the thickness and refractive index of the base layer of the marker to obtain the second out-of-plane rotation angle.

[0017] In one embodiment, the moiré spatial frequency includes a first frequency and a second frequency, the moiré phase shift includes a first phase shift corresponding to the first frequency and a second phase shift corresponding to the second frequency; and determining the second out-of-plane rotation angle of the marker based on the moiré image in the optical image further includes:

[0018] determining a first offset corresponding to the first phase shift according to the first frequency, and determining a second offset corresponding to the second phase shift according to the second frequency;

[0019] determining, according to the thickness and refractive index of the substrate layer, a third out-of-plane rotation angle corresponding to the first offset and a fourth out-of-plane rotation angle corresponding to the second offset;

[0020] The third out-of-plane rotation angle is combined with the fourth out-of-plane rotation angle to obtain the second out-of-plane rotation angle.

[0021] In one embodiment, before determining the incident light offset corresponding to the moiré phase shift of the moiré image according to a preset moiré spatial frequency, the method further includes:

[0022] determining position information of the moiré image in the optical image according to a first feature point image corresponding to a first feature point in the marker;

[0023] segmenting the moiré image from the optical image based on the position information;

[0024] A moiré phase shift in the moiré image is determined.

[0025] In one embodiment, obtaining the initial position information of the marker according to the feature point image in the optical image includes:

[0026] The initial position and posture information of the marker is determined according to the second feature point image corresponding to the second feature point in the marker.

[0027] In one embodiment, after obtaining the motion information of the detection object according to the rotation angle, the method further includes:

[0028] According to the motion information of the detected object, scanning parameters of the medical imaging scan are adjusted; the scanning parameters include at least one of scanning time, scanning angle and scanning position.

[0029] In a second aspect, the present application also provides a motion tracking system suitable for medical imaging scanning. The system includes a scanner, a camera, a light source, and a marker. The scanner has a scanning cavity, and a detection object is accommodated in the scanning cavity. The detection object is provided with the marker comprising moiré patterns and feature points.

[0030] The light source is used to illuminate the marker;

[0031] The camera is used to obtain an optical image of the marker during a medical imaging scan, determine the rotation angle of the marker based on the optical image, and obtain motion information of the detection object according to the rotation angle; the rotation angle includes at least one of an in-plane rotation angle and an out-of-plane rotation angle.

[0032] In one embodiment, the marker includes a front surface, a base layer and a back surface, the front surface is provided with a first grating structure, the base layer is made of a transparent material, and the back surface is provided with a second grating structure. Both the first grating structure and the second grating structure contain orthogonal gratings, and the orthogonal gratings in the first grating structure and the orthogonal gratings in the second grating structure have different spatial frequencies.

[0033] In one embodiment, the front surface is further provided with first characteristic points, including a starting point and an ending point of the orthogonal grating in the first grating structure.

[0034] In one embodiment, the front surface is further provided with second feature points, including at least one of black dots in the white circular area of the front surface, corner points of polygons in the white circular area, and preset patterns in the white circular area.

[0035] In a third aspect, the present application further provides a motion tracking device suitable for medical imaging scanning. The medical scanning device for performing medical imaging scanning includes a scanner, a camera, and a light source. The scanner has a scanning cavity, and a detection object is accommodated in the scanning cavity. The detection object is provided with a marker including moiré patterns and feature points. The device includes:

[0036] an image acquisition module, configured to acquire an optical image of the marker using the camera during the medical imaging scan process; the marker is illuminated by the light source;

[0037] an angle determination module, configured to determine a rotation angle of the marker based on the optical image; the rotation angle comprising at least one of an in-plane rotation angle and an out-of-plane rotation angle;

[0038] The information determination module is used to obtain the motion information of the detection object according to the rotation angle.

[0039] In a fourth aspect, the present application further provides a computer device. The computer device includes a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the following steps are implemented:

[0040] During the medical imaging scan, the camera is used to obtain an optical image of the marker; the marker is illuminated by the light source;

[0041] Determining a rotation angle of the marker based on the optical image; the rotation angle includes at least one of an in-plane rotation angle and an out-of-plane rotation angle;

[0042] According to the rotation angle, motion information of the detection object is obtained.

[0043] In a fifth aspect, the present application further provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the following steps:

[0044] During the medical imaging scan, the camera is used to obtain an optical image of the marker; the marker is illuminated by the light source;

[0045] Determining a rotation angle of the marker based on the optical image; the rotation angle includes at least one of an in-plane rotation angle and an out-of-plane rotation angle;

[0046] According to the rotation angle, motion information of the detection object is obtained.

[0047] In a sixth aspect, the present application further provides a computer program product. The computer program product includes a computer program that, when executed by a processor, implements the following steps:

[0048] During the medical imaging scan, the camera is used to obtain an optical image of the marker; the marker is illuminated by the light source;

[0049] Determining a rotation angle of the marker based on the optical image; the rotation angle includes at least one of an in-plane rotation angle and an out-of-plane rotation angle;

[0050] According to the rotation angle, motion information of the detection object is obtained.

[0051] The above-mentioned motion tracking method, system, device, computer equipment, storage medium and computer program product suitable for medical imaging scanning use a camera to obtain an optical image of the marker during the medical imaging scanning process, determine the rotation angle of the marker based on the optical image, and obtain motion information of the detection object according to the rotation angle; the moiré phase shift in the optical image can be used to accurately determine the rotation angle of the marker. Since the marker is set on the detection object, a more accurate rotation angle of the detection object can be obtained, and then more accurate motion information of the detection object can be obtained. The detection object is motion tracked based on the motion information, thereby improving the accuracy of motion tracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 A diagram of an application environment of a motion tracking method suitable for medical imaging scanning in one embodiment;

[0053] Figure 2 is a schematic diagram of the front surface of a marker in one embodiment;

[0054] Figure 3 is a schematic diagram of the rear surface of a marker in one embodiment;

[0055] Figure 4 is a flow chart of a motion tracking method applicable to medical imaging scanning in one embodiment;

[0056] Figure 5 is a schematic diagram of out-of-plane rotation angles in one embodiment;

[0057] Figure 6 is a flow chart of a motion tracking method suitable for medical imaging scanning in another embodiment;

[0058] Figure 7is a block diagram of a motion tracking system suitable for medical imaging scanning in one embodiment;

[0059] Figure 8 is a block diagram of a motion tracking device suitable for medical imaging scanning in one embodiment;

[0060] Figure 9 FIG. 1 is a diagram showing the internal structure of a computer device in one embodiment. DETAILED DESCRIPTION

[0061] 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.

[0062] The motion tracking method for medical imaging scanning provided in the embodiments of the present application can be applied to Figure 1 In the application environment shown. The detection object and the marker 104 form a rigid connection, so the position information of the marker 104 is the position information of the detection object. The marker 104 consists of a front surface, a base layer and a back surface. The base layer is a transparent material. In order to enhance the reflective performance of the back surface, a reflective film can be attached to the back surface. The front surface and the back surface are both provided with a grating structure. Figure 2 A schematic diagram of the front surface of a marker is provided. Figure 3 A schematic diagram of the rear surface of a marker is provided, according to Figure 2 and Figure 3 , grating structures include but are not limited to orthogonal gratings.

[0063] like Figure 1 As shown, a light source 102 and a camera 106 are positioned in front of a marker 104. The camera 106 can be any optical or digital camera capable of imaging based on received light waves, and the light source 102 can be an object capable of emitting light of a specified wavelength, such as an LED or light-emitting diode. The light source 102 illuminates the marker 104, with the light sequentially passing through the front surface and the substrate layer to the rear surface. Reflected by the rear surface, it forms reflected light, resulting in different periodic intervals (or spatial frequencies) in the grating structures on the front and rear surfaces of the marker 104. When the camera 106 is used to photograph the marker 104, an image containing moiré patterns is obtained. The camera 106 is connected to a scanner to transmit the image containing moiré patterns to a scanner used for medical imaging scans, including but not limited to magnetic resonance imaging scanners.

[0064] A spatial rectangular coordinate system is established with the center point of the initial state of the marker 104 as the origin O. The XOY plane of the spatial rectangular coordinate system is parallel to the front and back surfaces of the marker 104. The Z axis of the spatial rectangular coordinate system is perpendicular to the front and back surfaces of the marker 104. The position information of the marker 104 is represented by six degrees of freedom, including three translational degrees of freedom along the X, Y, and Z axes, and three rotational degrees of freedom around the X, Y, and Z axes. The three rotational degrees of freedom can be expressed by the inclination angle of the X axis. , Y-axis yaw angle and the Z-axis rotation angle To express.

[0065] In one embodiment, Figure 4 As shown, a motion tracking method suitable for medical imaging scanning is provided. The medical scanning device performing the medical imaging scan includes a scanner, a camera, and a light source. The scanner has a scanning cavity that accommodates a detection object, and a marker containing moiré patterns and feature points is provided on the detection object. The detection object can be a patient requiring a medical imaging scan. The method is described using a scanner as an example and includes the following steps:

[0066] Step S210 , during a medical imaging scan, an optical image of a marker is acquired by using a camera; the marker is illuminated by a light source.

[0067] The optical image may be an image obtained by photographing the marker with a camera when the marker is illuminated by a light source.

[0068] In a specific implementation, because the grating structures on the front and back surfaces of the marker have different periodic intervals (or spatial frequencies), a light source illuminates the marker, and a camera captures the marker, producing an optical image containing moiré patterns. As the object moves within the scanner's scanning chamber, the marker moves with it, causing the camera to capture the marker at preset intervals. This produces multiple optical images that change over time, each containing moiré patterns. The camera then transmits these moiré-containing images to the scanner.

[0069] Step S220: determining a rotation angle of the marker based on the optical image; the rotation angle includes at least one of an in-plane rotation angle and an out-of-plane rotation angle.

[0070] The in-plane rotation angle may be the angle at which the marker rotates around the Z axis, and the out-of-plane rotation angle may be the angle at which the marker rotates around the X axis or the Y axis.

[0071] In a specific implementation, feature points can be set on the marker, and the optical image captured by the camera contains images of the feature points. The scanner can preliminarily determine the six-degree-of-freedom pose information of the marker based on the images of the feature points, including the in-plane rotation angle, out-of-plane rotation angle, and translation information of the three degrees of freedom. In addition, when the marker rotates around the X-axis or Y-axis, the moiré in the optical image will translate accordingly, and the amount of translation can be measured by the moiré phase shift. Therefore, there is a certain mapping relationship between the out-of-plane rotation angle of the marker and the moiré phase shift in the optical image. The scanner can pre-acquire the mapping relationship between the out-of-plane rotation angle and the moiré phase shift. After acquiring multiple optical images that change over time, it measures the phase change of the moiré in different optical images to obtain the moiré phase shift corresponding to the different optical images. According to the pre-acquired mapping relationship, a more accurate out-of-plane rotation angle of the marker can be obtained based on the moiré phase shift.

[0072] In practical applications, the PnP (Perspective-n-Point) algorithm can be used, but is not limited to, to preliminarily determine the six-degree-of-freedom pose information of the marker, including the translation along the X, Y, and Z axes. 、 、 , and the tilt angle , yaw angle , rotation angle .

[0073] Figure 5 A schematic diagram of the out-of-plane rotation angle is provided. Figure 5 , assuming that the spatial frequency of the grating on the front surface of the marker is , the spatial frequency of the rear surface grating is , the front surface grating is parallel to the back surface grating, then the spatial frequency of the moiré pattern in the optical image is , assuming the thickness of the base layer of the marker is , the out-of-plane rotation angle of the marker is , the refractive index of air is The refractive index of the substrate is , as the marker rotates, the incident light shifts between the front and back surfaces by , the corresponding moiré phase shift is , thus obtaining the moiré phase shift Rotation angle with marker The mapping relationship between them is

[0074]

[0075] To determine the markers from Time to The out-of-plane rotation angle at the moment can be obtained separately 、 Optical image of the moment 、 ,Measurement and Moiré phase shift , according to the above formula, the rotation angle is obtained , as a marker from Time to When the grating structures on the front and back surfaces are both orthogonal gratings, the out-of-plane rotation angle Can include marker tilt angles and yaw angle .

[0076] Step S230: obtaining motion information of the detection object according to the rotation angle.

[0077] Among them, the motion information can be the six-degree-of-freedom posture information of the detection object, including three translational degrees of freedom of the detection object along the X, Y, and Z axes, and three rotational degrees of freedom around the X, Y, and Z axes, respectively. Among them, the three rotational degrees of freedom include tilt angle, yaw angle, and rotation angle.

[0078] In a specific implementation, the scanner can fuse the out-of-plane rotation angle obtained based on the moiré phase shift with the out-of-plane rotation angle determined based on the feature point image, and use the fused out-of-plane rotation angle, the in-plane rotation angle determined based on the feature point image, and the translation information of the three translation degrees of freedom as the motion information of the marker. Since the marker forms a rigid connection with the detection object, the motion information of the marker is the motion information of the detection object.

[0079] In practical applications, the tilt angle obtained in step S220 can be used , yaw angle To replace the tilt angle obtained by the PnP algorithm , yaw angle , get more accurate six-degree-of-freedom pose information of the marker 、 、 、 、 、 ,Will 、 、 、 、 、 As the six-degree-of-freedom pose information of the detection object.

[0080] The above-mentioned motion tracking method uses a camera to obtain an optical image of the marker during the medical imaging scanning process, determines the rotation angle of the marker based on the optical image, and obtains the motion information of the detection object according to the rotation angle; the moiré phase shift in the optical image can be used to accurately determine the rotation angle of the marker. Since the marker is set on the detection object, a more accurate rotation angle of the detection object can be obtained, and then more accurate motion information of the detection object can be obtained. The detection object is motion tracked based on the motion information, thereby improving the accuracy of motion tracking.

[0081] In one embodiment, the above-mentioned motion information includes six-degree-of-freedom posture information, and the above-mentioned step S220 may specifically include: obtaining the initial posture information of the marker based on the feature point image in the optical image; the initial posture information includes the in-plane rotation angle, the first out-of-plane rotation angle and translation information; determining the second out-of-plane rotation angle of the marker based on the moiré image in the optical image; fusing the second out-of-plane rotation angle with the first out-of-plane rotation angle to obtain the out-of-plane rotation angle of the marker; the target posture information of the marker includes the in-plane rotation angle, the out-of-plane rotation angle and translation information.

[0082] The feature point image may be an image of feature points in the optical image, and the moiré image may be an image of moiré patterns in the optical image.

[0083] The first out-of-plane rotation angle may be an out-of-plane rotation angle determined based on the optical image, and the translation information may be translation amounts of three translational degrees of freedom determined based on the optical image.

[0084] The second out-of-plane rotation angle may be an out-of-plane rotation angle determined according to a moiré phase shift in the moiré image. The target pose information may be the six-degree-of-freedom pose information finally determined for pose tracking.

[0085] In a specific implementation, feature points can be set on the marker, and grating structures with different periodic intervals can be set on the front and back surfaces of the marker. When a light source is illuminated on the marker, the marker is photographed using a camera to obtain an optical image. The feature points form a feature point image in the optical image, and the grating structure forms a moiré image in the optical image. The scanner can first determine the in-plane rotation angle, first out-of-plane rotation angle, and translation information of the marker based on the feature point image, then measure the moiré phase shift of the moiré image in the adjacent optical image, determine a second out-of-plane rotation angle based on the moiré phase shift, and fuse the second out-of-plane rotation angle with the first out-of-plane rotation angle to serve as the out-of-plane rotation angle of the marker. The in-plane rotation angle, out-of-plane rotation angle, and translation information are then used as the target position information of the marker.

[0086] In practical applications, based on the feature point image in the optical image, the PnP algorithm can be used to preliminarily determine the initial pose information of the marker, including the translation along the X, Y, and Z axes. 、 、 , that is, translation information, and tilt angle , yaw angle , that is, the first out-of-plane rotation angle, and the rotation angle , which is the in-plane rotation angle. As the marker rotates out of the plane, the moiré pattern in the optical image will shift, forming a moiré phase shift. Assuming that the spatial frequency of the grating on the front surface of the marker is , the spatial frequency of the rear surface grating is , the front surface grating is parallel to the back surface grating, then the spatial frequency of the moiré pattern in the optical image is , assuming the thickness of the base layer of the marker is , the out-of-plane rotation angle of the marker is , the refractive index of air is The refractive index of the substrate is , as the marker rotates out of plane, the incident light shifts between the front and back surfaces by , the corresponding moiré phase shift is , thus obtaining the moiré phase shift Rotation angle with marker The mapping relationship between them is

[0087]

[0088] Get them separately 、 Optical image of the moment 、 ,Measurement and Moiré phase shift , according to the above formula, the rotation angle is obtained , as a marker from Time to The second out-of-plane rotation angle at the moment. In the case where the grating structures on the front and back surfaces are both orthogonal gratings, the second out-of-plane rotation angle Can include marker tilt angles , yaw angle . Use tilt angle , yaw angle To replace the tilt angle obtained by the PnP algorithm , yaw angle , we can get a more accurate out-of-plane rotation angle of the marker, and the target pose information of the marker is 、 、 、 、 、 .

[0089] In this embodiment, the initial posture information of the marker is obtained based on the feature point image in the optical image; the initial posture information includes the in-plane rotation angle, the first out-of-plane rotation angle and translation information; the second out-of-plane rotation angle of the marker is determined based on the moiré image in the optical image; the second out-of-plane rotation angle is merged with the first out-of-plane rotation angle to obtain the out-of-plane rotation angle of the marker; the target posture information of the marker includes the in-plane rotation angle, the out-of-plane rotation angle and translation information, and the moiré phase shift can be used to accurately determine the out-of-plane rotation angle of the marker, thereby obtaining more accurate six-degree-of-freedom posture information.

[0090] In one embodiment, the above-mentioned step of determining the second out-of-plane rotation angle of the marker based on the moiré image in the optical image may specifically include: determining the incident light offset corresponding to the moiré phase shift of the moiré image based on a preset moiré spatial frequency; the incident light offset includes the offset of the incident light between the front surface and the back surface of the marker; and transforming the incident light offset based on the thickness and refractive index of the base layer of the marker to obtain the second out-of-plane rotation angle.

[0091] The moiré spatial frequency may be the spatial frequency of the grating on the rear surface of the marker.

[0092] The incident light offset may be an offset of the incident light between the front surface and the rear surface of the marker during the movement of the marker.

[0093] In a specific implementation, the scanner can pre-acquire a mapping relationship between the moiré phase shift and the incident light offset, using this mapping relationship as a first mapping relationship, where the first mapping relationship is associated with the spatial frequency of the moiré. The scanner can also pre-acquire a mapping relationship between the incident light offset and the out-of-plane rotation angle of the marker, using this mapping relationship as a second mapping relationship, where the second mapping relationship is associated with the thickness and refractive index of the marker's substrate layer. After measuring the moiré phase shift, the scanner can obtain the incident light offset corresponding to the moiré phase shift based on the first mapping relationship, and then transform the incident light offset based on the second mapping relationship to obtain the second out-of-plane rotation angle of the marker.

[0094] In practical applications, the spatial frequency of the grating on the front surface of the marker is , the spatial frequency of the rear surface grating is , the front surface grating is parallel to the back surface grating, then the spatial frequency of the moiré pattern in the optical image is , assuming the incident light offset is , then the moiré phase shift is , the moiré phase shift is measured After that, according to the first mapping relationship , get the incident light offset .

[0095] refer to Figure 5 , assuming the thickness of the marker base layer is , the refractive index of air is The refractive index of the substrate is , the out-of-plane rotation angle of the marker is , then the incident light offset is , the incident light offset is determined according to the first mapping relationship After that, according to the second mapping relationship , the incident light offset Transformed into the out-of-plane rotation angle of the marker , which is the second out-of-plane rotation angle.

[0096] In this embodiment, the incident light offset corresponding to the moiré phase shift of the moiré image is determined based on a preset moiré spatial frequency; the incident light offset includes the offset of the incident light between the front surface and the back surface of the marker; the incident light offset is transformed according to the thickness and refractive index of the base layer of the marker to obtain a second out-of-plane rotation angle. The out-of-plane rotation angle of the marker can be determined by measuring the moiré phase shift. Since the moiré phase shift can reflect extremely small angular rotations, accurate measurement of the out-of-plane rotation angle of the marker can be achieved.

[0097] In one embodiment, the moiré spatial frequency includes a first frequency and a second frequency, and the moiré phase shift includes a first phase shift corresponding to the first frequency and a second phase shift corresponding to the second frequency; the above-mentioned step of determining the second out-of-plane rotation angle of the marker based on the moiré image in the optical image may further specifically include: determining a first offset corresponding to the first phase shift based on the first frequency, and determining a second offset corresponding to the second phase shift based on the second frequency; determining a third out-of-plane rotation angle corresponding to the first offset and a fourth out-of-plane rotation angle corresponding to the second offset based on the thickness and refractive index of the substrate layer; and fusing the third out-of-plane rotation angle with the fourth out-of-plane rotation angle to obtain the second out-of-plane rotation angle.

[0098] The moiré phase shift may be a phase change of the moiré in different optical images.

[0099] The first frequency and the second frequency are two different spatial frequencies. The first phase shift may be a moiré phase shift corresponding to the first frequency, and the second phase shift may be a moiré phase shift corresponding to the second frequency. The first offset may be an incident light offset determined based on the first frequency and the first phase shift, and the second offset may be an incident light offset determined based on the second frequency and the second phase shift. The third out-of-plane rotation angle may be an out-of-plane rotation angle of the marker determined based on the first offset, and the fourth out-of-plane rotation angle may be an out-of-plane rotation angle of the marker determined based on the second offset.

[0100] In a specific implementation, a grating with a spatial frequency of the fundamental frequency can be set on any surface of the marker, and two gratings with different spatial frequencies can be set on the other surface of the marker, where the spatial frequency of one grating is higher than the fundamental frequency, and the spatial frequency of the other grating is lower than the fundamental frequency. In this way, two moiré patterns can be formed in the optical image acquired by the scanner, and the respective moiré phase shifts are measured to obtain the first phase shift and the second phase shift. The incident light offset corresponding to the moiré phase shift is first determined according to the first frequency and the second frequency, respectively, to obtain the first offset and the second offset. Then, the out-of-plane rotation angle of the marker corresponding to the incident light offset is determined according to the first offset and the second offset, respectively, to obtain the third out-of-plane rotation angle and the fourth out-of-plane rotation angle. Then, the out-of-plane rotation angle of the marker, i.e., the second out-of-plane rotation angle, can be obtained according to the third out-of-plane rotation angle and the fourth out-of-plane rotation angle.

[0101] In practical applications, the spatial frequency of the grating on the front surface of the marker is assumed to be the fundamental frequency There are two gratings on the back surface, both parallel to the grating on the front surface, with spatial frequencies of 、 ,in, 、 , then the spatial frequency of the moiré pattern in the optical image is 、 , and The signs are opposite, so the measured moiré phase shift 、 In the opposite direction, first according to 、 Calculate the first offset and the second offset , and then according to 、 Calculate the third plane rotation angle and the fourth plane rotation angle , and then the third out-of-plane rotation angle can be used and the fourth plane rotation angle To determine the second out-of-plane rotation angle , but not limited to obtaining the second out-of-plane rotation angle according to the average or weighted average of the third out-of-plane rotation angle and the fourth out-of-plane rotation angle, for example, ,or ,in, and The preset weights.

[0102] In this embodiment, a first offset corresponding to a first phase shift is determined according to a first frequency, and a second offset corresponding to a second phase shift is determined according to a second frequency; a third out-of-plane rotation angle corresponding to the first offset and a fourth out-of-plane rotation angle corresponding to the second offset are determined according to the thickness and refractive index of the substrate layer; the third out-of-plane rotation angle is combined with the fourth out-of-plane rotation angle to obtain the second out-of-plane rotation angle, and the two moiré patterns can be used to determine the out-of-plane rotation angle of the marker, thereby increasing the accuracy of determining the out-of-plane rotation angle of the marker.

[0103] In one embodiment, before the above-mentioned step of determining the incident light offset corresponding to the moiré phase shift of the moiré image based on the pre-set moiré spatial frequency, the method may further include: determining the position information of the moiré image in the optical image based on the first feature point image corresponding to the first feature point in the marker; segmenting the moiré image from the optical image based on the position information; and determining the moiré phase shift in the moiré image.

[0104] The first feature point may be a feature point used to mark a position of a moiré pattern, and the first feature point image may be an image of the first feature point captured by a camera.

[0105] The position information of the moiré pattern may be the position coordinates of the moiré pattern in the optical image.

[0106] In a specific implementation, a first feature point can be set on the grating on the front surface or the back surface of the marker, so that the multiple optical images captured and changing with time all contain the first feature point image. The scanner can determine the position information of the moiré patterns in different optical images based on the first feature point, segment the moiré pattern image from the optical image based on the position information, and compare the moiré pattern images in different optical images to obtain the moiré pattern phase shift corresponding to the changing time of the different optical images.

[0107] refer to Figure 2 , a cross point “+” can be set at the starting position and the ending position of the orthogonal grating on the front surface of the marker as the first feature point. Time to The moiré phase shift at each moment can be obtained separately 、 Optical image of the moment 、 , and 、 The cross points in the feature extraction are used to determine 、 The position coordinates of the moiré pattern are obtained from 、 Segment the moiré image from the image and compare the two segmented moiré images to obtain the moiré image from the image. Time to Moiré phase shift at a moment.

[0108] In this embodiment, the position information of the moiré image in the optical image is determined based on the first feature point image corresponding to the first feature point in the marker; the moiré image is segmented from the optical image based on the position information; and the moiré phase shift in the moiré image is determined. The moiré image can be accurately extracted from the optical image through the first feature point, and the moiré phase shift can be accurately determined.

[0109] In one embodiment, the step of obtaining the initial position and posture information of the marker according to the feature point image in the optical image may specifically include: determining the initial position and posture information of the marker according to the second feature point image corresponding to the second feature point in the marker.

[0110] The second feature point may be a feature point used to determine six-degree-of-freedom pose information. The second feature point image may be an image of the second feature point captured by a camera. The initial pose information may be six-degree-of-freedom pose information determined based on the second feature point.

[0111] In a specific implementation, a second feature point can be set on the marker, and the camera shoots the marker. The obtained optical image contains a second feature point image of the second feature point. The scanner can extract the second feature point image from the optical image and determine the initial posture information of the marker based on the second feature point image.

[0112] refer to Figure 2 , a black solid dot "·" can be set in the white circular area on the front surface of the marker, a polygon can be set in the white circular area, and a crosshair pattern " " and petal-shaped patterns" ", using the above-mentioned black solid dots, polygonal corner points, crosshair pattern, and petal-shaped pattern as second feature points, extract the second feature point image from the captured optical image, and determine the six-degree-of-freedom pose information of the marker based on the PnP algorithm, etc., as the initial pose information of the marker. Since the marker is rigidly connected to the detection object, the initial pose information of the marker is also the initial pose information of the detection object.

[0113] In this embodiment, by determining the initial posture information of the marker based on the second feature point image corresponding to the second feature point in the marker, the initial posture information can be quickly determined through the second feature point, thereby improving the speed of determining the target posture information and increasing the real-time performance of motion tracking.

[0114] In one embodiment, after the above step S230, the method may further include: adjusting scanning parameters of the medical imaging scan according to the motion information of the detected object; the scanning parameters include at least one of scanning time, scanning angle and scanning position.

[0115] The scanning time may be the start and end time of the scanner scanning the test object. The scanning angle may be the angle of the scanner relative to the test object during the scanning process. The scanning position may be the relative position of the scanner to the test object during the scanning process. The scanning angle and scanning position can be adjusted by adjusting the test object.

[0116] In a specific implementation, after determining the motion information of the detection object, the scanner can adjust the scanning parameters of the scanner for performing medical imaging scanning on the detection object in real time according to the motion information, including at least one of the scanning time, scanning angle and scanning position.

[0117] In practical applications, the scanner can adjust the scanning time, scanning angle, scanning position, etc. in real time according to the motion information of the detection object to obtain higher quality scanned images. Taking magnetic resonance scanning as an example, the initial posture of a specified voxel of the detection object can be determined based on the optical image at the initial moment, and the initial posture is used as a reference standard. During the magnetic resonance scanning process, the difference between the real-time posture of the detection object and the initial posture is determined based on the optical image acquired in real time, and the posture of the voxel of the detection object is adjusted in real time based on the difference. In addition, when it is necessary to correct translational motion, the image in the slice and readout direction can be moved by changing the center frequency of the RF pulse and the receiver. When it is necessary to correct translation in the phase encoding direction, the receiver phase can be modulated during the acquisition process or phase shifted during the reconstruction process.

[0118] In this embodiment, by adjusting the scanning parameters of the medical imaging scan according to the motion information of the detected object, the scanning parameters can be adjusted in real time according to the motion information, thereby ensuring the imaging quality of the medical imaging scan.

[0119] In one embodiment, Figure 6 As shown, a motion tracking method suitable for medical imaging scanning is provided. The method is described by taking the application of the method to a scanner as an example, and includes the following steps:

[0120] Step S301, during a medical imaging scan, an optical image of a marker is acquired using a camera; the marker is illuminated by a light source;

[0121] Step S302, determining initial position information of the marker according to the second feature point image corresponding to the second feature point in the marker; the initial position information includes an in-plane rotation angle, a first out-of-plane rotation angle, and translation information;

[0122] Step S303, determining a second out-of-plane rotation angle of the marker according to the moiré pattern image in the optical image;

[0123] Step S304: The second out-of-plane rotation angle is combined with the first out-of-plane rotation angle to obtain the out-of-plane rotation angle of the marker; the target posture information of the marker includes the in-plane rotation angle, the out-of-plane rotation angle and the translation information;

[0124] Step S305: obtaining motion information of the detection object according to the rotation angle; the rotation angle includes at least one of an in-plane rotation angle and an out-of-plane rotation angle;

[0125] Step S306 , adjusting the scanning parameters of the medical imaging scan according to the motion information of the detected object; the scanning parameters include at least one of a scanning time, a scanning angle, and a scanning position.

[0126] In a specific implementation, a camera can photograph a marker illuminated by a light source to obtain multiple optical images containing moiré patterns, which are then transmitted to a scanner. The scanner determines the position of the moiré patterns in the optical image based on the first feature point, extracts the moiré pattern image based on the moiré pattern position, and then obtains the moiré pattern phase shift corresponding to different optical images. According to a preset mapping relationship, the incident light offset corresponding to the moiré pattern phase shift and the out-of-plane rotation angle of the marker corresponding to the incident light offset are determined to obtain the out-of-plane rotation angles corresponding to different optical images, and the out-of-plane rotation angle is used as the out-of-plane rotation angle of the detection object rigidly connected to the marker. After determining the initial posture information of the marker, the out-of-plane rotation angle is used to replace the tilt angle and yaw angle in the initial posture information to obtain the motion information of the detection object.

[0127] The above-mentioned motion tracking method can use the moiré phase shift in the optical image to accurately determine the rotation angle of the marker. Since the marker is set on the detection object, a more accurate rotation angle of the detection object can be obtained, and then more accurate motion information of the detection object can be obtained. The detection object is tracked according to the motion information, thereby improving the accuracy of motion tracking.

[0128] In one embodiment, Figure 7 As shown, a motion tracking system suitable for medical imaging scanning is provided, including a scanner 108, a camera 106, a light source 102 and a marker 104; the scanner 108 has a scanning cavity and a detection object is accommodated in the scanning cavity, and the detection object is provided with a marker 104 including moiré patterns and feature points;

[0129] a light source 120 for illuminating the marker 104;

[0130] The camera 106 is used to obtain an optical image of the marker 104 during a medical imaging scan, determine a rotation angle of the marker 104 based on the optical image, and obtain motion information of the detection object according to the rotation angle; the rotation angle includes at least one of an in-plane rotation angle and an out-of-plane rotation angle.

[0131] In a specific implementation, the detection object can be rigidly connected to the marker, and the light source can illuminate the marker to form reflected light on the marker. The camera can shoot the marker to obtain multiple optical images containing moiré patterns. The camera can measure the moiré phase shift corresponding to different optical images, and determine the out-of-plane rotation angle of the marker corresponding to the moiré phase shift according to a preset mapping relationship. The out-of-plane rotation angle is used as the out-of-plane rotation angle of the detection object. The camera can also determine the initial posture information of the marker, and use the initial posture information of the marker as the initial posture information of the detection object. The initial posture information is integrated with the out-of-plane rotation angle to obtain the motion information of the detection object, thereby realizing motion tracking of the detection object.

[0132] The above-mentioned motion tracking system uses a camera to obtain an optical image of the marker during the medical imaging scanning process, determines the rotation angle of the marker based on the optical image, and obtains the motion information of the detection object according to the rotation angle; the moiré phase shift in the optical image can be used to accurately determine the rotation angle of the marker. Since the marker is set on the detection object, a more accurate rotation angle of the detection object can be obtained, and then more accurate motion information of the detection object can be obtained. The detection object is motion tracked based on the motion information, thereby improving the accuracy of motion tracking.

[0133] In one embodiment, the above-mentioned marker includes a front surface, a base layer and a rear surface, the front surface is provided with a first grating structure, the base layer is made of a transparent material, and the rear surface is provided with a second grating structure. Both the first grating structure and the second grating structure contain orthogonal gratings, and the orthogonal gratings in the first grating structure and the orthogonal gratings in the second grating structure have different spatial frequencies.

[0134] The first grating structure may be a grating structure on the front surface, and the second grating structure may be a grating structure on the back surface.

[0135] In a specific implementation, the marker may include a front surface, a base layer, and a back surface. The base layer may be, but is not limited to, a transparent material such as glass or acrylic. A reflective film may also be attached to the base layer to enhance the reflective performance. The front surface and the back surface may be, but are not limited to, formed by depositing chemical substances on the base layer by means of printing, photolithography, or vapor deposition. The front surface and the back surface respectively include a first grating structure and a second grating structure. Since the moiré pattern formed by the superposition of two parallel one-dimensional gratings only reflects the rotation angle of one dimension, in order to measure the tilt angle and yaw angle, orthogonal gratings may be set in the first grating structure and the second grating structure to achieve rotation angle measurement in two orthogonal dimensions. At the same time, the orthogonal gratings in the first grating structure and the orthogonal gratings in the second grating structure need to have different spatial frequencies to form a difference in spatial frequency, which displays moiré patterns in the optical image.

[0136] In this embodiment, the marker includes a front surface, a base layer and a back surface, the front surface is provided with a first grating structure, the base layer is made of a transparent material, and the back surface is provided with a second grating structure. Both the first grating structure and the second grating structure contain orthogonal gratings, and the orthogonal gratings in the first grating structure and the orthogonal gratings in the second grating structure have different spatial frequencies. Moiré patterns can be formed in the optical image, and the out-of-plane rotation angle is measured by the moiré patterns, thereby improving the accuracy of the out-of-plane rotation angle measurement.

[0137] In one embodiment, the front surface is further provided with first characteristic points, including a starting point and an ending point of the orthogonal grating in the first grating structure.

[0138] The first characteristic point may be a starting point and an ending point of the front surface orthogonal grating.

[0139] In a specific implementation, a first feature point can be set on the front surface of the marker so that the optical image captured by the camera contains the first feature point image. The first feature point can be a cross intersection "+" at the starting position and the ending position of the orthogonal grating on the front surface of the marker.

[0140] In this embodiment, by further providing the front surface with first characteristic points, including the starting point and the ending point of the orthogonal grating in the first grating structure, the moiré image can be accurately extracted from the optical image, and the moiré phase shift can be accurately determined.

[0141] In one embodiment, the front surface is further provided with second characteristic points, including at least one of black points in the white circular area of the front surface, corner points of polygons in the white circular area, and preset patterns in the white circular area.

[0142] The second feature point may be, but is not limited to, a black point in the white circular area of the front surface, a polygonal corner point, and a preset pattern.

[0143] In a specific implementation, a second feature point can be set on the front surface of the marker, so that the second feature point image can be extracted from the optical image captured by the camera, and the six-degree-of-freedom pose information of the marker can be determined based on the second feature point image. The second feature point can be a black solid dot "·" in the white circular area on the front surface of the marker, a corner point of a polygon in the white circular area, a crosshair pattern " "Or petal-shaped pattern" "At least one of the following.

[0144] In this embodiment, by providing the front surface with a second feature point, including black dots in the white circular area of the front surface, corner points of the polygon in the white circular area, and at least one of the preset patterns in the white circular area, the initial posture information can be quickly determined, the speed of determining the motion information is improved, and the real-time performance of motion tracking is increased.

[0145] In order to facilitate those skilled in the art to have a deeper understanding of the embodiments of the present application, a specific example will be used for illustration below.

[0146] This application proposes a moiré marker that can achieve high-precision head motion tracking. Based on this moiré marker, high-precision and high-stability six-degree-of-freedom pose estimation can be achieved using a single camera, thereby solving the problems of low accuracy and lack of robustness in traditional motion tracking methods.

[0147] like Figure 1 As shown, the motion tracking system can consist of a camera 106, a light source 102, and a moiré marker 104. The camera 106 forms an optical image by recording the light reflected from the light source 102 after it strikes the marker 104, thereby acquiring spatial information about the marker. The marker 104 comprises a three-layer structure: a front surface, a base layer, and a back surface. The front and back surfaces can be formed by depositing chemicals on the base layer through printing, photolithography, or vapor deposition. The base layer can be made of a transparent material such as glass or acrylic. The back surface can also be coated with a reflective film to enhance reflectivity and improve optical image quality. The marker 104 can be rigidly connected to the tracked object (e.g., a head) through adhesive, binding, or other means. Therefore, the six-degree-of-freedom information of the marker 104 reflects the six-degree-of-freedom information of the object.

[0148] Take the center point of the marker in its initial state as the origin to establish Figure 1 The six-degree-of-freedom information of the marker 104 includes the translation along the X-axis, Y-axis and Z-axis and the rotation around the X-axis, Y-axis and Z-axis, wherein the rotation around the X-axis, Y-axis and Z-axis can be expressed as the tilt angle. , yaw angle and rotation angle The front and rear surfaces of the marker 104 correspond to the XOY plane. Rotation about the X and Y axes can be called out-of-plane rotation, and rotation about the Z axis can be called in-plane rotation.

[0149] like Figure 2 and Figure 3 As shown, grating structures with different periodic intervals can be printed on the front and back surfaces of the marker, creating alternating light and dark black and white stripes in the captured optical image, known as moiré patterns. Moiré patterns can shift with the rotation of the marker, and the amount of this shift can be measured as the phase change of the moiré pattern, known as moiré phase shift. Even very small rotations can cause visible moiré phase shifts, enabling precise rotation angle measurement.

[0150] Assume that the spatial frequencies of the gratings on the front and back surfaces of the marker are and , then the spatial frequency of the moiré pattern is When calculating the moiré phase shift, the refraction effect of the substrate between the front and back surfaces needs to be considered. Assume that the thickness of the substrate is d and the rotation angle of the marker is , due to the refractive index of air Refractive index of the substrate Different, the light incident on the front surface is offset between the front and back surfaces of the base layer, and the offset is , the corresponding moiré phase shift is Therefore, when the marker rotates, the rotation angle of the marker can be obtained by measuring the phase shift of the moiré pattern.

[0151] The moiré pattern formed by the superposition of two parallel one-dimensional gratings is only sensitive to rotation in that dimension, so it can only measure the rotation angle in one dimension. Printing orthogonal gratings on the front and back surfaces respectively can achieve rotation angle measurement in two orthogonal dimensions. These two orthogonal dimensions are usually selected from the X-axis and Y-axis corresponding to the initial state of the marker.

[0152] Since the spatial frequency of the moiré pattern is approximately In general, the camera is far away from the marker, which corresponds to the far-field condition. However, in the head motion tracking scenario, the camera is close to the head and the marker. At this time, due to the existence of the near-field effect, the spatial frequency of the rear surface grating Slight variations may occur, resulting in corresponding shifts in the spatial frequency of the moiré. To avoid affecting motion tracking accuracy, a baseband grating can be printed on one surface of the marker, while two gratings with different frequencies—one above the baseband and the other below—are printed on the other surface. This allows the moiré patterns formed by the two gratings to shift in opposite directions. This design allows for differential measurement of the moiré phase shift, avoiding the influence of near-field effects and improving the accuracy of rotation angle measurements.

[0153] like Figure 2 As shown, a cross-point "+" can be designed on the front surface to accurately locate the starting and ending positions of the moiré pattern. By extracting features from the cross-points and combining them with the grating size of the front and back surfaces, the position coordinates of the moiré pattern in the optical image can be obtained, thereby accurately segmenting the moiré pattern area in the optical image and determining the moiré pattern phase shift.

[0154] In addition to using moiré patterns to achieve high-precision rotation measurement, multiple feature points can also be set to achieve high-precision measurement of the three translational degrees of freedom and rough estimation of the three rotational degrees of freedom. These feature points mainly include the black solid dots “·” in the white circular area of the front surface. By extracting these feature points, the scaling and deformation relationship from the 3D world coordinate system to the 2D image coordinate system can be used to estimate the six-degree-of-freedom pose information of the marker.

[0155] In addition, the above black solid dot “·” can be surrounded by polygons with different numbers of sides, for example, 、 、 These polygons provide a large number of feature points. After extracting the corner points of these polygons, the accuracy of the 6DOF pose estimation can be further improved based on the PnP pose estimation method.

[0156] In addition, a series of crosshair patterns can be printed in the border area of the marker. " and petal-shaped patterns" ", through machine learning or traditional image processing methods, the crosshairs pattern can be accurately located" " and petal-shaped patterns" " and other feature points, further effectively improving the accuracy of six-degree-of-freedom pose estimation.

[0157] The aforementioned motion tracking system utilizes moiré patterns to achieve high-precision rotation angle measurement, addressing the low accuracy of rotation angle measurement in traditional motion tracking technologies. Furthermore, it also provides a method for high-precision moiré position measurement using multiple feature points, addressing the low accuracy of position measurement in traditional motion tracking technologies. Furthermore, it provides a differential measurement method to mitigate measurement bias caused by the near-field effect in head motion tracking.

[0158] 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.

[0159] Based on the same inventive concept, the present application also provides a motion tracking device for implementing the aforementioned motion tracking 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 of the following motion tracking device embodiments can be found in the above-mentioned limitations of the motion tracking method and will not be repeated here.

[0160] In one embodiment, Figure 8 As shown, a motion tracking device suitable for medical imaging scanning is provided. The medical scanning equipment performing medical imaging scanning includes a scanner, a camera, and a light source. The scanner has a scanning cavity, and the scanning cavity accommodates a detection object. The detection object is provided with a marker including moiré patterns and feature points. The above-mentioned device includes: an optical image module 410, a rotation angle module 420, and a motion information module 430, wherein:

[0161] The optical imaging module 410 is configured to obtain an optical image of the marker using the camera during the medical imaging scanning process; the marker is illuminated by the light source;

[0162] A rotation angle module 420 is configured to determine a rotation angle of the marker based on the optical image; the rotation angle includes at least one of an in-plane rotation angle and an out-of-plane rotation angle;

[0163] The motion information module 430 is configured to obtain motion information of the detection object according to the rotation angle.

[0164] In one embodiment, the above-mentioned rotation angle module 420 is also used to obtain the initial posture information of the marker based on the feature point image in the optical image; the initial posture information includes the in-plane rotation angle, the first out-of-plane rotation angle and the translation information; based on the moiré image in the optical image, the second out-of-plane rotation angle of the marker is determined; the second out-of-plane rotation angle is merged with the first out-of-plane rotation angle to obtain the out-of-plane rotation angle of the marker; the target posture information of the marker includes the in-plane rotation angle, the out-of-plane rotation angle and the translation information.

[0165] In one embodiment, the rotation angle module 420 is further configured to determine an incident light offset corresponding to a moiré phase shift of the moiré image based on a preset moiré spatial frequency; the incident light offset includes an offset of the incident light between the front surface and the rear surface of the marker; and the incident light offset is transformed based on the thickness and refractive index of the base layer of the marker to obtain the second out-of-plane rotation angle.

[0166] In one embodiment, the rotation angle module 420 is further configured to determine a first offset corresponding to the first phase shift based on the first frequency, and a second offset corresponding to the second phase shift based on the second frequency; determine a third out-of-plane rotation angle corresponding to the first offset and a fourth out-of-plane rotation angle corresponding to the second offset based on the thickness and refractive index of the substrate layer; and combine the third out-of-plane rotation angle with the fourth out-of-plane rotation angle to obtain the second out-of-plane rotation angle.

[0167] In one embodiment, the rotation angle module 420 is further used to determine the position information of the moiré image in the optical image based on the first feature point image corresponding to the first feature point in the marker; segment the moiré image from the optical image based on the position information; and determine the moiré phase shift in the moiré image.

[0168] In one embodiment, the rotation angle module 420 is further configured to determine the initial position information of the marker according to a second feature point image corresponding to a second feature point in the marker.

[0169] In one embodiment, the motion tracking device further includes a parameter adjustment module for adjusting the scanning parameters of the medical imaging scan according to the motion information of the detected object; the scanning parameters include at least one of scanning time, scanning angle and scanning position.

[0170] Each module in the aforementioned motion tracking device may be implemented in whole or in part through software, hardware, or a combination thereof. Each module may be embedded in or independent of a processor within a computer device in the form of hardware, or may be stored in a computer device memory in the form of software, so that the processor can call and execute the corresponding operations of each module.

[0171] In one embodiment, a computer device is provided. The computer device may be a terminal, and its internal structure diagram may be as follows: Figure 9 As shown. The computer device includes a processor, memory, an input / output interface, a communication interface, a display unit, and an input device. The processor, memory, and input / output interface are connected via a system bus, and the communication interface, display unit, and input device are connected to the system bus via the input / output interface. 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 internal memory. The non-volatile storage medium stores an operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The input / output interface of the computer device is used to exchange information between the processor and external devices. The communication interface of the computer device is used to communicate with external terminals via wired or wireless means, and the wireless means can be achieved via Wi-Fi, mobile cellular networks, NFC (near-field communication), or other technologies. When executed by the processor, the computer program implements a motion tracking method. The display unit of the computer device is used to form a visually visible image and can be a display screen, a projection device, or a virtual reality imaging device. The display screen can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device can be a touch layer covering the display screen, or a button, trackball or touchpad set on the computer device casing, or an external keyboard, touchpad or mouse.

[0172] Those skilled in the art will understand that Figure 9 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.

[0173] 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.

[0174] 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.

[0175] 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.

[0176] 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, and the collection, use and processing of relevant data must comply with the relevant laws, regulations and standards of relevant countries and regions.

[0177] 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.

[0178] 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.

[0179] 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 motion tracking method suitable for medical imaging scanning, characterized in that: A medical scanning device for performing medical imaging scanning includes a scanner, a camera, and a light source. The scanner has a scanning cavity, and a detection object is accommodated in the scanning cavity. A marker including moiré patterns and feature points is provided on the detection object. The method includes: During the medical imaging scan, the camera is used to obtain an optical image of the marker; the marker is illuminated by the light source; Determining a rotation angle of the marker based on the optical image; the rotation angle includes at least one of an in-plane rotation angle and an out-of-plane rotation angle; According to the rotation angle, motion information of the detection object is obtained.

2. The method according to claim 1, characterized in that The motion information includes six-degree-of-freedom posture information; and determining the rotation angle of the marker based on the optical image includes: Obtaining initial position information of the marker according to the feature point image in the optical image; the initial position information includes the in-plane rotation angle, the first out-of-plane rotation angle and translation information; determining a second out-of-plane rotation angle of the marker according to a moiré pattern image in the optical image; The second out-of-plane rotation angle is merged with the first out-of-plane rotation angle to obtain the out-of-plane rotation angle of the marker; the target posture information of the marker includes the in-plane rotation angle, the out-of-plane rotation angle and the translation information.

3. The method according to claim 2, characterized in that Determining a second out-of-plane rotation angle of the marker according to the moiré pattern image in the optical image includes: determining, according to a preset moiré spatial frequency, an incident light offset corresponding to a moiré phase shift of the moiré image; the incident light offset comprising an offset of the incident light between a front surface and a rear surface of the marker; The incident light offset is transformed according to the thickness and refractive index of the base layer of the marker to obtain the second out-of-plane rotation angle.

4. The method according to claim 3, characterized in that The moiré spatial frequency includes a first frequency and a second frequency, and the moiré phase shift includes a first phase shift corresponding to the first frequency and a second phase shift corresponding to the second frequency; The determining the second out-of-plane rotation angle of the marker according to the moiré pattern image in the optical image further includes: determining a first offset corresponding to the first phase shift according to the first frequency, and determining a second offset corresponding to the second phase shift according to the second frequency; determining, according to the thickness and refractive index of the substrate layer, a third out-of-plane rotation angle corresponding to the first offset and a fourth out-of-plane rotation angle corresponding to the second offset; The third out-of-plane rotation angle is combined with the fourth out-of-plane rotation angle to obtain the second out-of-plane rotation angle.

5. The method according to claim 3, characterized in that Before determining the incident light offset corresponding to the moiré phase shift of the moiré image according to the preset moiré spatial frequency, the method further includes: determining position information of the moiré image in the optical image according to a first feature point image corresponding to a first feature point in the marker; segmenting the moiré image from the optical image based on the position information; A moiré phase shift in the moiré image is determined.

6. The method according to claim 2, characterized in that The obtaining of the initial position information of the marker according to the feature point image in the optical image includes: The initial position and posture information of the marker is determined according to the second feature point image corresponding to the second feature point in the marker.

7. The method according to claim 1, characterized in that After obtaining the motion information of the detection object according to the rotation angle, the method further includes: According to the motion information of the detected object, scanning parameters of the medical imaging scan are adjusted; the scanning parameters include at least one of scanning time, scanning angle and scanning position.

8. A motion tracking system suitable for medical imaging scanning, characterized in that: The system includes a scanner, a camera, a light source and a marker, wherein the scanner has a scanning cavity in which a detection object is accommodated, and the marker including moiré patterns and feature points is provided on the detection object; The light source is used to illuminate the marker; The camera is used to obtain an optical image of the marker during a medical imaging scan, determine the rotation angle of the marker based on the optical image, and obtain motion information of the detection object according to the rotation angle; the rotation angle includes at least one of an in-plane rotation angle and an out-of-plane rotation angle.

9. The system according to claim 8, characterized in that The marker includes a front surface, a base layer and a back surface, the front surface is provided with a first grating structure, the base layer is made of a transparent material, and the back surface is provided with a second grating structure. Both the first grating structure and the second grating structure contain orthogonal gratings, and the orthogonal gratings in the first grating structure and the orthogonal gratings in the second grating structure have different spatial frequencies.

10. The system according to claim 9, characterized in that The front surface is further provided with first characteristic points, including a starting point and an ending point of the orthogonal grating in the first grating structure.

11. The system according to claim 9, wherein: The front surface is further provided with second characteristic points, including at least one of black points in the white circular area of the front surface, corner points of a polygon in the white circular area, and a preset pattern in the white circular area.

Images