Magnetic resonance gating method, device, terminal and medium based on laser speckle image

Abstract

This invention provides a magnetic resonance imaging (MRI) gating method, device, terminal, and medium based on laser speckle images, specifically relating to the fields of image processing and physiological monitoring. The solution includes: acquiring a sequence of defocused interferometric speckle images of the heart under laser illumination within a preset time period using a single camera, based on a pre-defined spatiotemporal mapping model; obtaining a composite motion signal of the heart based on the defocused interferometric speckle image sequence; determining the temporal phase characteristics of the heart based on the composite motion signal; and extracting cardiac vibration and respiratory motion signals using a pre-defined gating strategy in response to the detection of the temporal phase characteristics. The novel composite gating strategy proposed in this solution relies solely on a single defocused camera, offering advantages such as non-contact operation, high precision, and robustness to disturbances caused by magnetic fields. It simplifies the MRI process, provides a more comfortable user experience, and effectively eliminates respiratory and cardiac motion artifacts present during MRI.

Description

Technical Field

[0001] The present invention relates to the technical field of image processing and physiological monitoring, and in particular to a magnetic resonance gating method, device, terminal and medium based on laser speckle images. Background Art

[0002] Cardiovascular Magnetic Resonance (CMR) is a non-invasive medical imaging technology that can provide high-resolution cardiovascular images for evaluating cardiac structure and function, as well as related vascular systems such as the aorta and coronary arteries, providing important support for the diagnosis and treatment of cardiovascular diseases. However, CMR imaging often has motion artifacts.

[0003] In the existing technology, gating technology is often used to overcome the generation of motion artifacts. Gating technology uses external signals to trigger image acquisition in synchronization with the heart cycle, thereby effectively reducing cardiac periodic motion artifacts. Commonly used gating technologies include electrocardiogram (ECG) gating and pulse wave (PPG) gating. ECG gating is easily interfered by strong magnetic fields, and PPG gating has conduction time differences, both of which are prone to cause cardiac motion artifacts. It can be seen that the quality of cardiac magnetic resonance images collected using existing ECG gating technology is poor, and it is impossible to accurately extract cardiac motion signals. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide a magnetic resonance gating method, device, terminal and medium based on laser speckle images, aiming to solve the problem in the prior art that the quality of the acquired cardiac magnetic resonance images is poor and the cardiac motion signals cannot be accurately extracted.

[0005] In order to achieve the above-mentioned object, the present invention provides a first aspect of a magnetic resonance gating method based on laser speckle images, which is applied to a magnetic resonance gating device based on laser speckle images, wherein the device comprises a camera and a laser lamp, and comprises the following steps:

[0006] Based on a preset spatiotemporal mapping model, using the camera to collect a sequence of defocused interference speckle images of the heart under the irradiation of the laser light within a preset time period;

[0007] Based on the defocused interference speckle image sequence, a composite motion signal of the heart is obtained, wherein the composite motion signal is composed of cardiac motion and respiratory motion;

[0008] Determining a timing phase characteristic of the heart based on the composite motion signal;

[0009] In response to detecting the timing phase feature, a preset gating strategy is used to extract the heart vibration signal and the respiratory motion signal.

[0010] Optionally, based on a preset spatiotemporal mapping model, using the camera to collect a sequence of defocused interference speckle images of the heart under the irradiation of the laser light within a preset time period includes:

[0011] Based on a preset spatiotemporal mapping model, irradiating a preset position of the heart with the laser light;

[0012] The camera is used to collect a sequence of defocused interference speckle images of the heart within a preset time period.

[0013] Optionally, obtaining the composite motion signal of the heart based on the defocused interference speckle image sequence includes:

[0014] Based on the defocused interferometric speckle image sequence, obtaining a defocused speckle signal;

[0015] An optical flow algorithm is used to extract the defocused speckle signal to obtain a composite motion signal of the heart.

[0016] Optionally, determining the timing phase characteristics of the heart based on the composite motion signal includes:

[0017] Dividing the composite motion signal according to the motion stages of the heart to determine composite motion signal segments corresponding to each motion stage of the heart;

[0018] Feature extraction is performed according to the time sequence of the composite motion signal segments corresponding to all the motion stages to determine the time sequence phase features of the heart.

[0019] Optionally, in response to detecting the timing phase feature, extracting the heart vibration signal and the respiratory motion signal using a preset gating strategy includes:

[0020] In response to detecting a preset respiratory motion feature point and a preset heartbeat motion feature point;

[0021] After the respiratory motion feature point is detected, if one or more cardiac motion feature points are detected in the same respiratory cycle, a nuclear magnetic resonance scan is triggered to obtain an image of a phase corresponding to each cardiac motion feature point to obtain cardiac image data;

[0022] Reconstructing the heartbeat image data based on the time series phase feature to obtain a heart motion signal;

[0023] A respiratory motion signal is obtained based on the composite motion signal and the cardiac motion signal.

[0024] Optionally, in response to detecting the timing phase feature, extracting the heart vibration signal and the respiratory motion signal using a preset gating strategy includes:

[0025] In response to detecting a preset respiratory motion feature point and a preset heartbeat motion feature point;

[0026] After the respiratory motion feature point is detected, if the cardiac motion feature point is detected in the same respiratory cycle, a nuclear magnetic resonance scan is triggered to scan an image of the entire cardiac motion cycle to obtain cardiac image data;

[0027] Reconstructing the heartbeat image data based on the time series phase feature to obtain a heart motion signal;

[0028] A respiratory motion signal is obtained based on the composite motion signal and the cardiac motion signal.

[0029] A second aspect of the present invention provides a magnetic resonance gating device based on laser speckle images, the device comprising at least one camera and at least one laser light, and further comprising:

[0030] A space-time mapping model building module, used to build a space-time mapping model based on the position of the camera and the heart of the subject;

[0031] A defocused speckle image acquisition module, used to acquire a defocused interference speckle image sequence of the heart under the irradiation of the laser light within a preset time period using the camera based on a preset spatiotemporal mapping model;

[0032] A composite motion signal extraction module, used for obtaining a composite motion signal of the heart based on the defocused interference speckle image sequence, wherein the composite motion signal is composed of cardiac motion and respiratory motion;

[0033] A timing phase feature extraction module, used to determine the timing phase feature of the heart based on the composite motion signal;

[0034] The signal separation module is used to extract the heart vibration signal and the respiratory motion signal by using a preset gating strategy in response to detecting the timing phase feature.

[0035] A third aspect of the present invention provides a terminal, comprising a memory, a processor, and a laser speckle image-based magnetic resonance gating program stored in the memory and executable on the processor, wherein the laser speckle image-based magnetic resonance gating program, when executed by the processor, implements any one of the steps of the laser speckle image-based magnetic resonance gating method.

[0036] A fourth aspect of the present invention provides a computer-readable storage medium, on which a laser speckle image-based magnetic resonance gating program is stored, and when the laser speckle image-based magnetic resonance gating program is executed by a processor, any step of the above-mentioned laser speckle image-based magnetic resonance gating method is implemented.

[0037] Compared with the prior art, the beneficial effects of this solution are as follows:

[0038] The present invention mainly uses a camera adjusted to a defocused state to capture laser interference speckle images reflected by the human chest cavity. Laser speckle cardiogram cardiovascular magnetic resonance gating does not need to contact the human body and is not affected by the strong magnetic field of magnetic resonance. By analyzing continuous speckle images, the camera-seismocardiography (Camera-SCG) can be accurately reconstructed, and the magnetic resonance system is triggered based on the reconstructed camera-seismocardiography signal according to the constructed new composite gating strategy, so as to synchronously extract the cardiac motion signal and the respiratory motion signal according to the laser speckle movement, which can effectively reduce the motion artifacts caused by the heart beat. The new composite gating strategy proposed by the present invention relies only on a single defocused camera, has the advantages of non-contact, high precision, and robustness to disturbances caused by magnetic fields, can simplify the magnetic resonance process, provide a more comfortable use experience, and can effectively eliminate the respiratory and cardiac motion artifacts in the magnetic resonance imaging process. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0040] Figure 1 For cardiovascular magnetic resonance imaging;

[0041] Figure 2 This is a flow chart of the magnetic resonance gating method based on laser speckle images of the present invention;

[0042] Figure 3 It is a schematic diagram of the rotational motion along the X-axis / Y-axis of the spatiotemporal mapping model between the heart beat and the speckle pixel motion of the present invention;

[0043] Figure 4 It is a schematic diagram of the translational movement along the Z axis of the spatiotemporal mapping model between the heart beat and the speckle pixel movement of the present invention;

[0044] Figure 5 It is a schematic diagram of the defocused speckle imaging and the corresponding optical flow field of the present invention;

[0045] Figure 6 A schematic diagram of dividing each movement phase of the heart of the present invention;

[0046] Figure 7 A normalized cardiac complex motion signal waveform diagram of the present invention;

[0047] Figure 8 A schematic diagram comparing multiple cardiovascular magnetic resonance gating triggering mechanisms based on cardiac motion signals of the present invention;

[0048] Fig. 9 It is a schematic diagram of a module of a magnetic resonance gating device based on laser speckle image of the present invention;

[0049] Fig.10 It is a schematic diagram of the terminal structure of the present invention. DETAILED DESCRIPTION

[0050] In the following description, specific details such as specific device structures, techniques, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details that hinder the description of the present invention.

[0051] It should be understood that when used in this specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0052] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0053] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0054] As used in this specification and the appended claims, the term "if" may be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if [described condition or event] is detected" may be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0055] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0057] In the face of the problem that the quality of cardiac magnetic resonance images collected by the existing ECG gating technology is poor and the cardiac motion signal cannot be accurately extracted, and considering the reasons for the poor quality of cardiac magnetic resonance images, the main reasons are that cardiac fluctuations, respiratory movements and other limb movements cause changes in tissue position and shape, causing image phase encoding errors or geometric deformation, resulting in motion artifacts such as blur, ghosting, stripes or flickering in the image, such as Figure 1 As shown. Therefore, the present invention proposes a magnetic resonance gating method based on laser speckle images, which mainly uses a defocused camera to capture laser interference speckle images reflected by the human chest cavity. The defocused camera laser speckle cardiogram cardiovascular magnetic resonance gating does not need to contact the human body and is not affected by the strong magnetic field of magnetic resonance. By analyzing continuous speckle images, the heart movement can be accurately reconstructed, and the magnetic resonance system is triggered to collect images based on the reconstructed Camera-SCG signal, which can effectively reduce the motion artifacts caused by heart beats. The composite gating strategy proposed in the present invention only relies on a single defocused camera, and has the advantages of non-contact, high precision, and robustness to disturbances caused by magnetic fields. It can also synchronously extract heart movement and respiratory movement from the movement of laser speckles, realizing a new type of composite gating, which can simplify the magnetic resonance process, provide a more comfortable user experience, and effectively eliminate respiratory and cardiac motion artifacts in the magnetic resonance imaging process.

[0058] An embodiment of the present invention provides a magnetic resonance gating method based on laser speckle images, which is deployed on electronic devices such as computers and servers and is applied to scenarios for monitoring the cardiac movement and respiratory movement of subjects such as humans or animals. It is aimed at the situation where a single-band laser is used to irradiate the subject's heart to collect a defocused interference speckle image for analyzing the subject's composite cardiac operation signal (including a cardiac motion signal and a respiratory motion signal).

[0059] The method of the present invention is applied to a magnetic resonance gating device based on laser speckle images, the device comprising a camera and a laser lamp, the laser lamp is used to emit a laser of a certain wavelength band to the position of the subject's heart, and the camera is used to collect the defocused speckle image of the subject's heart under the irradiation of the laser lamp. The device also comprises a spatiotemporal mapping model construction module, a defocused speckle image acquisition module, a composite motion signal extraction module, a time sequence phase feature extraction module and a signal separation module, the functions of which will be described in detail in the following implementation process of the magnetic resonance gating method based on laser speckle images.

[0060] Based on the device, the detailed process of the magnetic resonance gating method based on laser speckle image of the embodiment is as follows: Figure 2 As shown, the details are as follows:

[0061] Step S100: Based on a preset space-time mapping model, using the camera to collect a sequence of defocused interference speckle images of the heart under the irradiation of the laser light within a preset time period.

[0062] Specifically, since the condition for diffuse reflection is that the wavelength of light is smaller than the height of the fluctuation of the heart surface of the subject, the heart beat will be manifested in the form of microscopic vibration with an amplitude of 0.2-0.5mm on the chest surface. Therefore, in principle, light in the visible light band can be used for this solution. In order to better extract the speckle pattern generated under the irradiation of light in the future, this embodiment uses laser as the light source. Since the laser only contains light of a single wavelength, it has good singleness, which is conducive to accurately separating the speckle pattern corresponding to the laser wavelength. After a lot of research and experimental analysis, it is found that when the camera is in a defocused state, the interference speckle formed in the video after the laser irradiates and reflects on the human body surface not only does not become blurred, but instead presents a granular shape with alternating light and dark and strong contrast. The weak movement of the chest cavity caused by the heart beat will change the reflection direction of the laser on its surface, thereby causing the spatial distribution of the speckle interference fringes in the reflected light field to change, and the intensity of the change of the speckle interference fringes will significantly increase with the increase of the defocus degree of the camera, where the defocus degree represents the ratio of the distance between the subject's heart and the focal plane to the distance between the camera and the focal plane.

[0063] Therefore, this embodiment pre-constructs Figure 3The time-space mapping model shown is as follows: the camera and the subject's heart are arranged on both sides of the focal plane of the camera. When the camera is out of focus, the subject's heart moves to a distance from the focal plane. Taking the rotation of the subject's heart along the Y axis as an example, the initial incident angle of the laser is , the imaging angle of the camera is , when the subject's heart rotates a small angle along the Y axis The incident angle of the laser also changes by the same angle. The laser actually irradiates only a single pixel of the subject’s heart, but because the pixel is not on the focal plane, a speckle is generated on the camera imaging plane. The radial displacement of the speckle relative to the single pixel is The radial displacement is affected by two factors. First, the rotation of the subject's heart itself will cause the orientation of the subject's heart surface relative to the light source and the sensor to change at the same angle. , obviously, ; Second, the change in the angle of illumination caused by the rotational motion will cause the reflected light to produce additional rotation In order to observe the same speckle after the subject's heart rotates, the constraint condition that the speckle before and after rotation has the same initial phase difference (that is, the optical path difference before and after rotation remains unchanged) should be satisfied. Therefore, according to this constraint condition, the change of the illumination angle is defined to satisfy the form shown in formula (1), that is:

[0064] (1),

[0065] Usually the heart rotation angle of the subject is very small, and the equivalent infinitesimal substitution principle can be obtained. , then the radial displacement of the laser speckle on the camera imaging plane is The expression of is shown in formula (2), that is:

[0066] (2),

[0067] in, represents the distance between the subject's heart and the focal plane, represents the distance between the camera lens and the focal plane, Indicates focal length.

[0068] Taking into account the restriction that the light irradiation angle is equal to the camera imaging angle, equation (2) can be simplified as:

[0069] (3).

[0070] Similarly, when the subject's heart rotates along the X-axis, it will cause the pixels to move in the Y-direction of the camera imaging plane, and the expression of the motion displacement is the same as formula (2).

[0071] like Figure 4 As shown, when the camera is imaging vertically ( ), the translational motion of the subject's heart It will not cause the movement of pixels on the camera imaging plane. When the camera imaging has an angle ( ), the light irradiated to the same position on the heart surface of the subject will have an angle of The rotation of the heart is proportional to the out-of-plane displacement of the heart. dz is proportional to the size of ).in, is the irradiation distance. From the above analysis, we can know that and equal, The expression of is the same as that of formula (1). Therefore, the displacement of the speckle on the camera sensor along the X-axis can be obtained , as shown in formula (4):

[0072] (4).

[0073] Since the camera is much more sensitive to out-of-plane rotation than other motions when it is highly out of focus, Much smaller than , the displacement of pixels in the X direction on the camera plane can be simplified as:

[0074] (5),

[0075] in, is a constant.

[0076] Based on the above analysis, the sensitivity of the pixels on the camera imaging plane to the subject's heart movement in the X-axis and Y-axis directions is positively correlated with the camera's defocus degree, where the defocus degree represents the distance between the subject's heart and the focal plane. and the distance between the camera and the focal plane The ratio of . Therefore, in this embodiment, the defocus degree of the camera is adjusted by the spatiotemporal mapping model construction module to achieve different sensitivity settings for the heart movement of the subject, so that the focal plane is located between the camera and the heart of the subject, and the defocus degree is set within the corresponding ratio range according to the sensitivity requirements of the heart movement of the subject, and the spatial position relationship between the camera and the heart is determined; based on the spatial position relationship, the vibration signal of the heart within a preset time period is collected, and the defocused speckle image within the time period is collected by the camera to determine the temporal relationship between the vibration signal of the heart within the preset time period and the corresponding defocused speckle image movement; based on the spatial position relationship and the temporal relationship, a spatiotemporal mapping model between the heart beat and the speckle pixel movement is constructed. The motion monitoring method of the heart of the subject in this embodiment is completely different from the motion monitoring in traditional video imaging. In traditional video monitoring, the farther the camera is from the heart of the subject, the lower the sensitivity of the motion monitoring. Therefore, the imaging method of defocused interferometric speckle is particularly suitable for monitoring weak physiological movements at a long distance.

[0077] Then, a preliminary experiment was conducted on the imaging effect of the above-constructed spatiotemporal mapping model. In the experiment, the distance between the focal plane of the camera and the lens was controlled to adjust the defocus degree of the camera. Figure 5 As shown, in the two experiments, the laser lamp emits lasers of the same wavelength but the distance between the heart and the focal plane is different, which are respectively called the long object distance experiment and the short object distance experiment. By comparing the light interference results of the two experiments, it can be seen that both experiments have the situation of same-direction interference and reverse interference. Compared with the short object distance experiment, the particle size of the speckle generated by the long object distance experiment is larger, and the movement of the optical flow field is more obvious. It can be seen that in monitoring the laser interference phenomenon, as the distance between the heart and the focal plane increases (that is, the object distance is getting farther and farther), the particle size of the obtained speckle is also getting larger and the speckle movement is more sensitive (that is, the arrow representing the movement in the optical flow field is longer), which is consistent with the derivation conclusion related to the above-mentioned spatiotemporal mapping model between the heart beat and the speckle pixel movement. Based on this, according to the calculation accuracy and sensitivity requirements, this embodiment arranges the camera at a suitable distance from the subject to meet the requirements of the interference speckle to amplify the multiple of the heart vibration.

[0078] Then, based on the spatiotemporal mapping model, the laser light is used to illuminate different positions of the heart, and finally a suitable position is determined, which refers to a certain point on the ventricle or atrium, and does not deviate from the heart, which is conducive to improving the effectiveness and accuracy of the acquired defocused interference speckle image sequence; the defocused camera is used to collect the defocused interference speckle image sequence reflected by the human chest cavity within a preset time period through the defocused speckle image acquisition module, and the defocused interference speckle image sequence contains the defocused interference speckle of the reflection signal formed under the irradiation of the laser of a single band emitted by the laser light, wherein the preset time period refers to a period of time corresponding to several heart beat cycles, so as to ensure that the complete heart motion signal and respiratory motion signal can be extracted from the defocused interference speckle image sequence later. This embodiment uses a single defocus camera to collect the defocused interference speckle image of the heart, which has the advantages of non-contact, high precision, and robustness to disturbances caused by magnetic fields, and because the laser reflects the weak chest vibration caused by the heart beat, it has a smaller physiological delay than the pulse wave used in the pulse wave gating technology, and can capture a more accurate and sensitive heart motion state.

[0079] Step S200: obtaining a composite motion signal of the heart based on the defocused interference speckle image sequence, wherein the composite motion signal is composed of cardiac motion and respiratory motion.

[0080] Specifically, since defocused interference speckles corresponding to the laser band are generated under the irradiation of the laser emitted by the laser lamp, and each pixel in the defocused speckle image is composed of pixel values ​​of three channels of RGB, the present embodiment extracts the defocused speckle signal contained in each defocused speckle image in the defocused interference speckle image sequence according to the pixel channel through the composite motion signal extraction module, and since the defocused speckle signal is extracted from the laser speckle image under the optical mode, it will not be interfered by the magnetic field of the magnetic resonance system itself, so the defocused speckle signal has high accuracy; the defocused speckle signal is extracted from the laser speckle image under the optical mode and will not be interfered by the magnetic field of the magnetic resonance system itself, so the defocused speckle signal has high accuracy; the optical flow algorithm is used to extract the defocused speckle signal to obtain a composite motion signal, which is based on the cardiac motion and the respiratory motion, that is, the composite motion signal includes the cardiac vibration signal and the respiratory motion signal, specifically, the optical flow method is used to calculate the motion amplitude of the defocused speckle signal in the X and Y directions and cascade them into a motion amplitude sequence, and the motion amplitude sequence in the X and Y directions is divided into fragments, represented by , for all and , use formula (6) to determine the motion angle of the defocused speckle signal ,in Indicates the ninetieth digit amplitude value in the corresponding quadrant, It means taking the median, Represents the four quadrants in the Cartesian coordinate system, Indicates the number of the quadrant, .

[0081] (6),

[0082] in, represents the quadrant with the largest ninetieth digit among the four quadrants of the Cartesian rectangular coordinate system, represents the coordinates of any two-dimensional space point in the Cartesian rectangular coordinate system, and They represent the movement amplitude of the defocused speckle image in the X direction and the Y direction relative to the previous frame of defocused speckle image, Indicates the number of segments divided by sliding windows. The argmax function returns The parameter corresponding to the maximum value.

[0083] Obtain the motion angle of the defocused speckle signal Then, use formula (7) to and Synthesize into a composite motion signal of the heart , that is, Camera-SCG signal.

[0084] (7),

[0085] in, and Represents the composite motion signal of all sliding windows The magnitude of movement in the X direction and the magnitude of movement in the Y direction.

[0086] It can be seen that the essence of the Camera-SCG signal is the regular pixel motion information in the speckle image.

[0087] Step S300: Determine the timing phase characteristics of the heart based on the composite motion signal.

[0088] Specifically, since the movement stages of the heart mainly include systole and diastole, these two stages can be further subdivided into atrial systole (corresponding to the P wave on the electrocardiogram), ventricular isovolumetric contraction (from the beginning of the QRS complex to the S1 heart sound), ventricular rapid ejection period, ventricular slow ejection period, ventricular isovolumetric relaxation period (S2 heart sound to the beginning of the T wave), ventricular rapid filling period and ventricular slow filling period (atrial systole) and other movement stages. Among them, the starting point or end point of each movement stage in a heartbeat movement cycle includes the mitral valve closure (Mitral Valve Closure, MC) point, isovolumetric contraction (Inferior VenaCava, IVC) point, aortic valve opening (Aortic Valve Opening, AO) point, rapid ejection (Rapid Ejection, RE) point, aortic valve closure (Aortic Valve Closure, AC) point, mitral valve opening (Mitral Valve Opening, MO) point, rapid filling (Rapid Filling, RF) point, etc. Figure 6 shown.

[0089] Therefore, this embodiment divides the composite motion signal according to the movement stage of the heart through the timing phase feature extraction module to determine the composite motion signal segments corresponding to each movement stage of the heart; feature extraction is performed according to the timing of the composite motion signal segments corresponding to all the movement stages to determine the timing phase features of the heart, including signal feature data of different phases such as time tags, waveform features and frequency features. Among them, the time tag is used to indicate the start and end time of each stage, which can be determined by the R wave peak, P wave starting point, S1 heart sound and S2 heart sound on Camera-SCG. The waveform feature is used to indicate the waveform shape, amplitude, width, etc. of each stage, such as the shape of the QRS complex on Camera-SCG, the intensity and duration of the S1 heart sound and S2 heart sound. The frequency feature is used to indicate the frequency change of vibration or blood flow velocity caused by cardiac movement, which can be obtained by spectrum analysis and other methods.

[0090] Step S400: In response to detecting the timing phase feature, extracting the heart vibration signal and the respiratory motion signal using a preset gating strategy.

[0091] Specifically, since the movement of the chest plane is a composite movement composed of high-frequency weak heartbeat movement (about 0.5-3Hz) and low-frequency violent respiratory movement (about 0.1-1Hz), and the differential operation contained in the optical flow helps to amplify the weak movement of the heart, but weakens the low-frequency respiratory movement. Therefore, when the Camera-SCG signal is not normalized for trend and amplitude, the Camera-SCG signal is integrated in the time dimension to reconstruct the low-frequency respiratory motion signal, specifically by calculating the cumulative sum of each time point of the Camera-SCG time series. Then, the timing phase features of the reconstructed respiratory motion and cardiac motion are located, specifically, respiratory motion feature points and cardiac motion feature points are set through the signal separation module, and the respiratory motion feature points and cardiac motion feature points respectively represent the key signal features in the timing phase features of the reconstructed respiratory motion and cardiac motion, and are used to reflect the signal feature data corresponding to the start or end time of a respiratory motion cycle and a cardiac cycle. For example, one or more of the mitral valve closure (MC) point, isovolumetric contraction (IVC) point, aortic valve opening (AO) point, rapid ejection (RE) point, aortic valve closure (AC) point, mitral valve opening (MC) point, and rapid filling (RE) point can be selected as the characteristic points of heartbeat motion. The most important respiratory muscle involved in breathing, that is, the point where the contraction or relaxation state of the diaphragm is most obvious, is selected as the characteristic point of respiratory motion. The characteristic points in this embodiment are detected by peak location or machine learning algorithm.

[0092] In the same respiratory cycle, in response to the detection of both respiratory motion feature points and one or more cardiac motion feature points, the nuclear magnetic resonance scan is triggered to obtain the image of the phase corresponding to each cardiac motion feature point to ensure that a clear image is captured at a specific stage of cardiac motion corresponding to the respiratory motion feature point (such as a certain stage of ventricular contraction or diastole); then the cardiac image data is reconstructed based on the timing phase characteristics to trigger the reordering of a single-frame magnetic resonance image or multiple-frame magnetic resonance images to form a continuous and dynamic cardiac motion image, and a cardiac motion signal is extracted from the reconstructed cardiac motion image to describe the motion state of the heart in the entire cardiac cycle, including the contraction and relaxation of the ventricular wall, the volume change of the heart cavity, etc. This process optimizes the magnetic resonance image scanning by combining the feature points of respiratory and cardiac motion, which can effectively reduce the motion artifacts caused by respiratory motion on cardiac fluctuations and significantly improve the accuracy and clarity of cardiac imaging. Finally, the cardiac motion signal is separated from the composite motion signal to obtain the respiratory motion signal.

[0093] This embodiment realizes the use of a single defocused camera to simultaneously collect a sequence of defocused interference speckle images of the heart motion under the combined action of respiratory motion and cardiac motion, and extracts the composite motion signal of the heart as the Camera-SCG signal, and successfully separates the low-frequency and intense respiratory motion signal and the high-frequency and weak cardiac motion signal contained in the composite motion signal by using a composite gating including respiratory and cardiac motion triggers.

[0094] For example, a laser is used to illuminate the fourth rib in the lower left part of the human chest cavity, and a speckle image of the laser reflection is captured by a defocus camera. By analyzing the heart motion state information contained in the laser speckle image, a periodic composite motion signal of the heart is constructed and a waveform diagram after normalization is obtained, such as Figure 7 As shown, the trigger point represents the cardiac motion feature point detected in the same respiratory cycle after the respiratory motion feature point is detected.

[0095] like Figure 8 As shown, in a preferred embodiment, in response to detecting the timing phase feature, a preset gating strategy is used to extract the heart vibration signal and the respiratory motion signal, including:

[0096] The respiratory motion feature points and the cardiac motion feature points are set by the signal separation module; in response to the detection of the respiratory motion feature points, if one or more cardiac motion feature points are detected in the same respiratory cycle, the nuclear magnetic resonance scan is triggered to obtain the image of the phase corresponding to each cardiac motion feature point, and the cardiac image data is obtained, that is, the respiratory motion feature points and the signal of the cardiac motion phase corresponding to each cardiac motion feature point as the starting point (i.e., the cardiac image data) are used as the gating signal, and the collected cardiac image data includes the phase data of one or more motion phases of interest in a cardiac cycle, and the phase data of other motion phases of no interest are not collected, which can significantly reduce the radiation dose of the subject; the cardiac image data is reconstructed based on the time sequence phase feature to obtain the cardiac motion signal, and during the reconstruction process, the image can be phase corrected and sorted with the help of the electrocardiogram (ECG) signal information to ensure the time sequence and phase accuracy of the image; based on the composite motion signal and the cardiac motion signal, the respiratory motion signal is obtained. The specific implementation steps can be referred to the above step S400, which will not be repeated here.

[0097] like Figure 8 As shown, in a preferred embodiment, in response to detecting the timing phase feature, a preset gating strategy is used to extract the heart vibration signal and the respiratory motion signal, including:

[0098] Set respiratory motion feature points and cardiac motion feature points; after the respiratory motion feature points are detected, if the cardiac motion feature points are detected within the same respiratory cycle, trigger the nuclear magnetic resonance to scan the image of the entire cardiac motion cycle to obtain cardiac image data, that is, use the respiratory motion feature points and the cardiac motion feature points as the starting point corresponding to the cardiac motion phase signal (i.e., cardiac image data) as the gating signal, and the collected cardiac image data includes the time phase data of a complete cardiac cycle. Compared with the prospective gating strategy, the radiation dose of the subject is higher; reconstruct the cardiac image data based on the timing phase characteristics to obtain the cardiac motion signal; obtain the respiratory motion signal based on the composite motion signal and the cardiac motion signal. The specific implementation steps can be found in the above step S400, which will not be repeated here.

[0099] like Fig. 9 As shown, corresponding to the above-mentioned magnetic resonance gating method based on laser speckle image, an embodiment of the present invention further provides a magnetic resonance gating device based on laser speckle image, wherein the above-mentioned magnetic resonance gating device based on laser speckle image includes at least one camera and at least one laser lamp, and further includes:

[0100] A defocused speckle image acquisition module 910 is used to acquire a defocused interference speckle image sequence of the heart under the irradiation of the laser light within a preset time period by using the camera based on a preset spatiotemporal mapping model;

[0101] A composite motion signal extraction module 920, configured to obtain a composite motion signal of the heart based on the defocused interferometric speckle image sequence, wherein the composite motion signal is composed of cardiac motion and respiratory motion;

[0102] A timing phase feature extraction module 930, for determining the timing phase feature of the heart based on the composite motion signal;

[0103] The signal separation module 940 is used to extract the heart vibration signal and the respiratory motion signal using a preset gating strategy in response to detecting the timing phase feature.

[0104] Specifically, in this embodiment, the specific functions of the magnetic resonance gating device based on laser speckle images can also refer to the corresponding description in the magnetic resonance gating method based on laser speckle images, which will not be repeated here.

[0105] Based on the above embodiment, the present invention further provides a terminal, whose principle block diagram can be shown as follows: Fig.10As shown. The terminal includes a processor, a memory, a network interface and a display screen connected via a system bus. The processor of the terminal is used to provide computing and control capabilities. The memory of the terminal includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a magnetic resonance gating program based on laser speckle images. The internal memory provides an environment for the operation of the operating system and the magnetic resonance gating program based on laser speckle images in the non-volatile storage medium. The network interface of the terminal is used to communicate with an external terminal via a network connection. When the magnetic resonance gating program based on laser speckle images is executed by the processor, the steps of any one of the magnetic resonance gating methods based on laser speckle images are implemented. The display screen of the terminal may be a liquid crystal display screen or an electronic ink display screen.

[0106] Those skilled in the art will understand that Fig.10 The principle block diagram shown in the figure is only a block diagram of a partial structure related to the scheme of the present invention, and does not constitute a limitation on the terminal to which the scheme of the present invention is applied. The specific terminal may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0107] In one embodiment, a terminal is provided, comprising a memory, a processor, and a laser speckle image-based magnetic resonance gating program stored in the memory and executable on the processor, wherein the laser speckle image-based magnetic resonance gating program, when executed by the processor, implements the steps of any one of the laser speckle image-based magnetic resonance gating methods provided in an embodiment of the present invention.

[0108] An embodiment of the present invention further provides a computer-readable storage medium, on which a magnetic resonance gating program based on laser speckle images is stored. When the magnetic resonance gating program based on laser speckle images is executed by a processor, the steps of any one of the magnetic resonance gating methods based on laser speckle images provided in the embodiments of the present invention are implemented.

[0109] It should be understood that the serial numbers of the steps in the above embodiments do not imply a sequence of execution, and the execution sequence of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0110] Those skilled in the art can clearly understand that, for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the above-mentioned device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of the present invention. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0111] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0112] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0113] In the embodiments provided by the present invention, it should be understood that the disclosed apparatus / terminal equipment and method can be implemented in other ways. For example, the apparatus / terminal equipment embodiments described above are only illustrative, for example, the division of the above modules or units is only a logical function division, and in actual implementation, other division methods can be used, for example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed.

[0114] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, it should be understood by those skilled in the art that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features therein may be replaced by equivalents. However, these modifications or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A magnetic resonance gating method based on laser speckle image, characterized in that: The invention is applied to a magnetic resonance gating device based on laser speckle images, the device comprising at least one camera and at least one laser light, and comprising the following steps: Based on a preset spatiotemporal mapping model, using the camera to collect a sequence of defocused interference speckle images of the heart under the irradiation of the laser light within a preset time period; Based on the defocused interference speckle image sequence, a composite motion signal of the heart is obtained, wherein the composite motion signal is composed of cardiac motion and respiratory motion; Determining a timing phase characteristic of the heart based on the composite motion signal; In response to detecting the timing phase feature, extracting the heart vibration signal and the respiratory motion signal using a preset gating strategy; In order to observe the same speckle after the heart of the subject rotates, the constraint condition that the speckle before and after the rotation has the same initial phase difference should be met. According to the constraint condition, the change of the illumination angle is defined to satisfy the following form: , the expression of the radial displacement of laser speckle on the camera imaging plane is: ; in, The change in the angle of illumination caused by the rotational motion will cause the reflected light to produce an additional rotation. The heart of the subject is rotated along the Y axis by an angle, is the initial incident angle of the laser, is the imaging angle of the camera, is the radial displacement of the laser speckle on the camera imaging plane, is the distance between the subject's heart and the focal plane, is the distance between the camera lens and the focal plane, is the focal length.

2. The magnetic resonance gating method based on laser speckle image according to claim 1, characterized in that: The method of collecting a sequence of defocused interference speckle images of the heart under the irradiation of the laser light within a preset time period by using the camera based on the preset spatiotemporal mapping model includes: Based on a preset spatiotemporal mapping model, irradiating a preset position of the heart with the laser light; The camera is used to collect a sequence of defocused interference speckle images of the heart within a preset time period.

3. The magnetic resonance gating method based on laser speckle image according to claim 1, characterized in that: The step of obtaining the composite motion signal of the heart based on the defocused interference speckle image sequence comprises: Based on the defocused interferometric speckle image sequence, obtaining a defocused speckle signal; An optical flow algorithm is used to extract the defocused speckle signal to obtain a composite motion signal of the heart.

4. The magnetic resonance gating method based on laser speckle image according to claim 1, characterized in that: Determining the timing phase characteristics of the heart based on the composite motion signal includes: Dividing the composite motion signal according to the motion stages of the heart to determine composite motion signal segments corresponding to each motion stage of the heart; Feature extraction is performed according to the time sequence of the composite motion signal segments corresponding to all the motion stages to determine the time sequence phase feature of the heart.

5. The magnetic resonance gating method based on laser speckle image according to any one of claims 1 to 4, characterized in that: In response to detecting the timing phase feature, extracting the heart vibration signal and the respiratory motion signal using a preset gating strategy includes: In response to detecting a preset respiratory motion feature point and a preset heartbeat motion feature point; After the respiratory motion feature point is detected, if one or more cardiac motion feature points are detected in the same respiratory cycle, a nuclear magnetic resonance scan is triggered to obtain an image of a phase corresponding to each cardiac motion feature point to obtain cardiac image data; Reconstructing the heartbeat image data based on the time series phase feature to obtain a heart motion signal; A respiratory motion signal is obtained based on the composite motion signal and the cardiac motion signal.

6. The magnetic resonance gating method based on laser speckle image according to any one of claims 1 to 4, characterized in that: In response to detecting the timing phase feature, extracting the heart vibration signal and the respiratory motion signal using a preset gating strategy includes: In response to detecting a preset respiratory motion feature point and a preset heartbeat motion feature point; After the respiratory motion feature point is detected, if the cardiac motion feature point is detected in the same respiratory cycle, a nuclear magnetic resonance scan is triggered to scan an image of the entire cardiac motion cycle to obtain cardiac image data; Reconstructing the heartbeat image data based on the time series phase feature to obtain a heart motion signal; A respiratory motion signal is obtained based on the composite motion signal and the cardiac motion signal.

7. A magnetic resonance gating device based on laser speckle image, characterized in that: The device comprises at least one camera and at least one laser light, and further comprises: A defocused speckle image acquisition module, used to acquire a defocused interference speckle image sequence of the heart under the irradiation of the laser light within a preset time period using the camera based on a preset spatiotemporal mapping model; A composite motion signal extraction module, used for obtaining a composite motion signal of the heart based on the defocused interference speckle image sequence, wherein the composite motion signal is composed of cardiac motion and respiratory motion; A timing phase feature extraction module, used to determine the timing phase feature of the heart based on the composite motion signal; A signal separation module, configured to extract a cardiac vibration signal and a respiratory motion signal using a preset gating strategy in response to detecting the timing phase feature; The magnetic resonance gating device based on laser speckle image is also used to observe the same speckle after the heart of the subject rotates, and the constraint condition that the speckle before and after the rotation has the same initial phase difference should be met. According to the constraint condition, the change of the irradiation angle is defined to meet the following form: , the expression of the radial displacement of laser speckle on the camera imaging plane is: ; in, The change in the angle of illumination caused by the rotational motion will cause the reflected light to produce an additional rotation. The heart of the subject is rotated along the Y axis by an angle, is the initial incident angle of the laser, is the imaging angle of the camera, is the radial displacement of the laser speckle on the camera imaging plane, is the distance between the subject's heart and the focal plane, is the distance between the camera lens and the focal plane, is the focal length.

8. A terminal, characterized in that: The terminal includes a memory, a processor, and a laser speckle image-based magnetic resonance gating program stored in the memory and executable on the processor, wherein the laser speckle image-based magnetic resonance gating program, when executed by the processor, implements the steps of the laser speckle image-based magnetic resonance gating method according to any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a magnetic resonance gating program based on a laser speckle image, and when the magnetic resonance gating program based on a laser speckle image is executed by a processor, the steps of the magnetic resonance gating method based on a laser speckle image are implemented as claimed in any one of claims 1 to 6.

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