Magnetic resonance imaging method, apparatus and device

Abstract

The application relates to a magnetic resonance imaging method, device, computer equipment, storage medium and computer program product. The method comprises the following steps: in a first cardiac cycle, a characteristic electrocardio signal of a detection object is identified, a first sequence pulse is applied to the detection object after a preset delay time of identifying the characteristic electrocardio signal, and the first sequence pulse is used for reversing a longitudinal magnetization vector of the detection object; after the first sequence pulse is applied, a second sequence pulse of a target phase mode is applied to the detection object after a recovery time, and an initial cardiac imaging set is acquired, wherein the target phase mode is one of at least two different phase modes, and different target phase modes correspond to different positions of artifacts in the initial cardiac imaging sets; and the initial cardiac imaging sets obtained in each first cardiac cycle are subjected to first registration processing to obtain a cardiac imaging. The method can effectively weaken the artifacts in cardiac delayed enhancement imaging, and does not increase additional operations and additional scanning time.

Description

Technical Field

[0001] This application relates to the field of magnetic resonance technology, and in particular to a magnetic resonance imaging method, apparatus and device. Background Technology

[0002] Magnetic resonance imaging (MRI) is a very powerful imaging method. This technique can obtain high-contrast, clear images of the interior of samples / tissues without damage or ionizing radiation, and has been widely used in various fields. Compared with other auxiliary imaging methods, MRI has advantages such as more imaging parameters, faster scanning speed, higher tissue resolution, and clearer images.

[0003] However, when performing delayed contrast-enhanced magnetic resonance imaging of the heart using traditional techniques, the final image often contains artifacts that are difficult to remove, resulting in poor imaging quality. Summary of the Invention

[0004] Therefore, it is necessary to provide a magnetic resonance imaging method, apparatus, computer equipment, storage medium, and computer program product that can produce fewer artifacts and better imaging results in response to the above-mentioned technical problems.

[0005] In a first aspect, embodiments of the present invention provide a magnetic resonance imaging method, comprising: during a first cardiac cycle, identifying electrocardiogram (ECG) characteristic signals of a detection object; after a preset delay time following the identification of the ECG characteristic signals, applying a first sequence pulse to the detection object, wherein the first sequence pulse is used to reverse the longitudinal magnetization vector signal of the detection object; after applying the first sequence pulse, and after a reversal recovery time, applying a second sequence pulse of a target phase mode to the detection object to obtain an initial cardiac imaging set, wherein the target phase mode is one of at least two different phase modes, and the positions of artifacts in the initial cardiac imaging set corresponding to different target phase modes are different; and performing a first registration process on the initial cardiac imaging set obtained in each first cardiac cycle to obtain cardiac images.

[0006] In one embodiment, the magnetic resonance imaging method further includes: in a second cardiac cycle following the first cardiac cycle, applying a third sequence of pulses of the same target phase pattern as the previous first cardiac cycle to the detection object to obtain a reference imaging set;

[0007] The step of performing a first registration process on the initial cardiac image set obtained in each first cardiac cycle to obtain cardiac images further includes: performing a first registration process on the reference image set obtained in each second cardiac cycle to obtain phase reference images; and performing a second registration process on the cardiac images using the phase reference images to obtain real part images of the cardiac images.

[0008] In one embodiment, the step of performing a first registration process on the initial cardiac image set obtained in each first cardiac cycle includes: selecting any one image in all the initial cardiac image sets as a reference image, registering the remaining initial cardiac images with the reference image as a reference to obtain each registered initial cardiac image; determining the first target pixel value of each pixel in each registered initial cardiac image, setting the pixel value of the corresponding pixel in the cardiac image according to each first target pixel value to obtain the cardiac image; wherein, the first target pixel value includes the maximum pixel value of the pixel in each registered initial cardiac image, or the average or median value of the pixel in each registered initial cardiac image.

[0009] In one embodiment, the step of selecting a reference image from all initial cardiac images and registering the remaining initial cardiac images with the reference image as a reference to obtain each registered initial cardiac image includes: selecting a reference image from each initial cardiac image corresponding to the same target phase mode, and registering the remaining initial cardiac images corresponding to the same target phase mode with the reference image as a reference to obtain each registered initial cardiac image.

[0010] In one embodiment, the step of performing a first registration process on the reference image set obtained in each second cardiac cycle to obtain a phase reference image includes: selecting any one image from all initial reference images as a reference image, registering the remaining reference images with the reference image as a reference to obtain each registered reference image; determining a second target pixel value for each pixel in each registered reference image, and setting the pixel value of the corresponding pixel in the phase reference image according to each second target pixel value to obtain a phase reference image; wherein, the second target pixel value includes the maximum pixel value of the pixel in each registered reference image, or the average or median value of the pixel in each registered reference image.

[0011] In one embodiment, the second sequence pulse includes multiple first excitation pulses, and the phase steps corresponding to different target phase modes are different. The step of applying the second sequence pulse of the target phase mode to the detection object to obtain an initial cardiac imaging set includes: applying multiple first excitation pulses to the detection object, wherein the phase difference of each adjacent first excitation pulse is the same as the phase step corresponding to the target phase mode; and obtaining the initial cardiac images corresponding to each first excitation pulse to obtain an initial cardiac imaging set.

[0012] In one embodiment, the step of identifying the electrocardiogram (ECG) characteristic signal of the detection object includes: acquiring the ECG trace of the detection object; identifying the R wave of the ECG trace, wherein the R wave is an ECG characteristic signal.

[0013] Secondly, embodiments of the present invention provide a magnetic resonance imaging apparatus, comprising: a first pulse module, configured to identify electrocardiogram (ECG) characteristic signals of a detection object during a first cardiac cycle, and apply a first sequence pulse to the detection object after a preset delay time following the identification of the ECG characteristic signals, the first sequence pulse being used to reverse the longitudinal magnetization vector signal of the detection object; a second pulse module, configured to apply a second sequence pulse of a target phase pattern to the detection object after applying the first sequence pulse and after a reversal recovery time, thereby acquiring an initial cardiac imaging set, wherein the target phase pattern is one of at least two different phase patterns, and the positions of artifacts in the initial cardiac imaging set corresponding to different target phase patterns are different; and a first registration module, configured to perform a first registration process on the initial cardiac imaging set obtained in each first cardiac cycle to obtain cardiac images.

[0014] Thirdly, embodiments of the present invention provide a magnetic resonance imaging device, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the magnetic resonance imaging method described above.

[0015] Fourthly, embodiments of the present invention provide a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the above-described magnetic resonance imaging method.

[0016] Based on any of the above embodiments, a first sequence of pulses is first used to invert the longitudinal magnetization vector signal of the detection object, and then a second sequence of pulses with different target phase modes are applied at different first cardiac cycles to acquire an initial cardiac imaging set with prominent contrast between normal and abnormal myocardium. Since the artifact locations differ within the initial cardiac imaging sets, effective information originally obscured by artifact regions can be extracted from corresponding regions of other initial cardiac imaging sets unaffected by artifacts. Based on this, a first registration process is performed on each initial cardiac imaging set to obtain cardiac images with weak or completely eliminated artifact regions. This magnetic resonance imaging method can effectively reduce artifacts in delayed-enhancement cardiac imaging, and since only the target phase mode is changed without adding additional scanning or acquisition processes, this embodiment is simple to implement and does not add extra operations or scanning time. Attached Figure Description

[0017] Figure 1 This is a diagram illustrating the application environment of a magnetic resonance imaging method in one embodiment.

[0018] Figure 2 This is a schematic flowchart of a magnetic resonance imaging method in one embodiment;

[0019] Figure 3 This is a timing diagram illustrating the application of pulses to the detection object in one embodiment;

[0020] Figure 4 This is a schematic diagram illustrating the working principle of the first sequence of pulses in one embodiment;

[0021] Figure 5 This is a flowchart illustrating a magnetic resonance imaging method in another embodiment;

[0022] Figure 6 This is a timing diagram illustrating the application of pulses to the detection object in another embodiment;

[0023] Figure 7 This is a schematic diagram of the phase changes of each first excitation pulse in the second sequence pulse in one embodiment;

[0024] Figure 8 This is a schematic diagram of the phase changes of each first excitation pulse in the second sequence pulse in another embodiment;

[0025] Figure 9 This is a schematic diagram of the process for performing a first registration process on an initial cardiac imaging set in one embodiment;

[0026] Figure 10 This is an internal structural diagram of a computer device in one embodiment;

[0027] Figure captions: 102 - Magnetic Resonance Scanner; 104 - Computer Equipment. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0029] The magnetic resonance imaging method provided in this application embodiment can be applied to, for example... Figure 1The application environment is shown. The magnetic resonance scanner 102 can communicate with the computer device 104. The computer device 104 can be, but is not limited to, various personal computers, laptops, smartphones, tablets, etc. The magnetic resonance scanner 102 and the computer device 104 can be in the same space, or the magnetic resonance scanner 102 can be located inside the scanning chamber, and the computer device 104 outside the scanning chamber. During magnetic resonance imaging, the object to be examined is carried on the bed of the magnetic resonance scanner 102. As the bed moves, the object is moved into an area where the main magnetic field is relatively uniformly distributed. The magnetic resonance scanner 102 generates radio frequency pulses. The radio frequency field formed by the radio frequency pulses can excite the nuclear spins within the object, thereby causing the object to generate magnetic resonance signals. Upon receiving the magnetic resonance signals generated by the object, the magnetic resonance signals are processed to form a magnetic resonance image. During the examination, parameters such as the scanning mode and scanning position can be changed by operating the computer device 104. Finally, the imaging results obtained by the magnetic resonance scanner 102 can also be transmitted to the computer device 104 for display. The magnetic resonance imaging method in this embodiment can be integrated into the magnetic resonance scanner 102. After obtaining the magnetic resonance signal generated by the excitation of the object being detected, a magnetic resonance image of the object can be obtained through Fourier transform. Alternatively, the magnetic resonance imaging method in this embodiment can be integrated into the computer device 104. The magnetic resonance scanner 102 transmits the magnetic resonance signal generated by the object being detected to the computer device 104, which then executes the magnetic resonance imaging method to obtain a magnetic resonance image.

[0030] In one embodiment, such as Figure 2 As shown, a magnetic resonance imaging method is provided, which is mainly used for delayed enhancement imaging of the heart of the object being detected, including steps S202 to S206.

[0031] S202, during the first cardiac cycle, the electrocardiogram characteristic signal of the detection object is identified, and after a preset delay time after the electrocardiogram characteristic signal is identified, a first sequence pulse is applied to the detection object. The first sequence pulse is used to reverse the longitudinal magnetization vector of the detection object.

[0032] A single contraction and relaxation of the heart constitutes a mechanical activity cycle, called a cardiac cycle. The first cardiac cycle can be any cardiac cycle during the entire magnetic resonance imaging (MRI) examination. Electrocardiographic (ECG) characteristic signals can reflect the arrival of a cardiac cycle. Specifically, identifying the ECG characteristic signals of the subject can include: acquiring the subject's ECG trace, identifying the R wave of the ECG trace, where the R wave is the ECG characteristic signal. The ECG R wave refers to the upward spike displayed on the ECG. In ECG gating technology, the ECG R wave is often used as a marker of the arrival of a cardiac cycle. After a preset delay following the ECG R wave, the heart enters diastole, a relatively static state, which can be used for the MRI scan.

[0033] Please see Figure 3 as well as Figure 4 Based on cardiac delayed enhancement imaging technology, after injecting contrast agent into the subject, under the excitation of the first sequence of pulses, the normal myocardium and abnormal myocardium of the subject's heart will feed back signal intensities of different strengths over time. Based on the difference in signal intensity, the heart of the subject can be diagnosed, thereby distinguishing between normal myocardial signals and abnormal myocardial signals. Figure 4 The abnormal myocardium shown can include infarcted myocardium and ischemic myocardium. After a period of time after the injection of contrast agent, the arrival of the first electrocardiogram cycle is determined by the R wave of the electrocardiogram. After the R wave of the electrocardiogram is detected and a preset delay time is passed, the application of the first sequence pulse can distinguish between normal myocardial signals and abnormal myocardial signals. That is, under the excitation of the first sequence pulse, the trend of changes in the signal intensity of normal myocardium, ischemic myocardium and infarcted myocardium is quite different, so the state of the heart of the subject can be confirmed.

[0034] In one embodiment, a gradient echo imaging sequence, such as a balanced steady-state free precession (GRE_BSSFP) imaging sequence, can be used when performing cardiac delayed-contrast imaging. During this magnetic resonance imaging process using the gradient echo imaging sequence, an inversion recovery (IR) pulse can be selected as the first sequence pulse; the inversion recovery pulse can invert the longitudinal magnetization vector signal.

[0035] S204, after applying the first sequence pulse, and after the inversion recovery time, apply the second sequence pulse of the target phase mode to the detection object to obtain an initial cardiac imaging set, wherein the target phase mode is one of at least two different phase modes, and the positions of artifacts in the initial cardiac imaging set corresponding to different target phase modes are different.

[0036] It is understandable that during magnetic resonance imaging (MRI) of the heart, many initial cardiac images need to be acquired to form initial cardiac image sets. The second sequence pulse includes multiple first excitation pulses. Each initial cardiac image in the initial cardiac image set is acquired by excitation from its corresponding first excitation pulse. The phase of each first excitation pulse in the second sequence pulse varies according to the selected target phase mode. After excitation by the first sequence pulse, the relaxation states of normal and abnormal myocardium differ; for example, normal and abnormal myocardium have different longitudinal relaxation times T1. The second sequence pulse can image the differences in relaxation states of different myocardial cells. However, for better imaging results, the second sequence pulse should be applied only after the longitudinal magnetization vector of normal myocardium has recovered to 0, i.e., after the first sequence pulse has been applied, and after the inversion recovery time (also known as the TI time) has elapsed.

[0037] Furthermore, different target phase modes will result in different artifact positions in the initial cardiac imaging sets. These artifacts can be black band artifacts, motion artifacts, etc., which are not limited in this embodiment. Currently, the same target phase mode is typically used for the second sequence pulses in each first cardiac cycle. This results in the artifact regions being located in essentially the same positions in the images obtained after registration for each initial cardiac imaging set, making it impossible to obtain effective information about the artifact regions from initial cardiac imaging sets corresponding to different first cardiac cycles. Therefore, this embodiment offers two or more selectable target phase modes, supporting the application of second sequence pulses with different target phase modes in different first cardiac cycles. The initial cardiac imaging sets obtained by applying second sequence pulses with different target phase modes will at least experience artifact region position shifts, allowing the extraction of effective artifact region information from each initial cardiac imaging set where the artifact region position shifts. For example, if the artifact region appears at position P1 in initial cardiac imaging set A1, and at position P2 in initial cardiac imaging set A2. Because the P1 position in the initial cardiac imaging set A1 is affected by artifacts, it is difficult to extract effective information. However, the P1 position in the initial cardiac imaging set A2 is not affected by artifacts, and effective information can be extracted from the P1 position in the initial cardiac imaging set A2. A similar approach can be used for the P2 position in the artifact region of the initial cardiac imaging set A2, which will not be elaborated further. Therefore, considering the initial cardiac imaging sets A1 and A2 together can eliminate the influence of artifacts.

[0038] S206, Perform the first registration process on the initial cardiac image set obtained in each first cardiac cycle to obtain cardiac images.

[0039] It is understandable that during the application of the second sequence pulses to obtain the initial imaging set, the subject may move due to excessive scanning time, or the scanning angle / RF emission angle may change due to other reasons. This may cause the position of organs or lesions at different time points to shift, ultimately leading to abnormal imaging results. Therefore, motion calibration is required for each initial cardiac imaging set obtained from the scan to reduce or eliminate the impact of lesion shift. The first registration process is used to perform motion calibration on the initial cardiac imaging sets obtained from each first cardiac cycle, and based on the above-mentioned approach to eliminate artifact regions, it combines each initial cardiac imaging set into a cardiac imaging set with very weak or no artifact regions. It is worth mentioning that the number of first cardiac cycles can be selected according to the actual situation, but it must include at least two first cardiac cycles with second sequence pulses of different target phase modes to reduce or eliminate artifact regions. In addition, since the breathing of the subject may cause displacement of the subject's organs, affecting the imaging effect, the subject may be required to hold their breath during the scan. However, since the first registration process is performed in this embodiment, the influence of respiratory motion can be eliminated, so free breathing magnetic resonance imaging of the subject can be supported. This embodiment is applicable to both breath-hold magnetic resonance imaging (MRI) and free-breathing MRI. The timing of step S206 is not limited in this embodiment; it can be performed after the entire scanning process is completed, or it can be performed during the scanning process on the initial cardiac image set obtained from each first cardiac cycle. Furthermore, each first cardiac cycle can be spaced between one or more cardiac cycles without the first sequence pulse applied, or they can be closely adjacent. No limitation is made here.

[0040] Based on the magnetic resonance imaging method in this embodiment, the longitudinal magnetization vector signal of the object is first detected by reversing a first sequence of pulses. Then, by applying a second sequence of pulses with different target phase modes during different first cardiac cycles, an initial cardiac imaging set with prominent contrast between normal and abnormal myocardium is acquired. Since artifacts in the initial cardiac imaging set are shifted, valid information originally obscured by artifacts can be extracted from corresponding regions of other initial cardiac imaging sets unaffected by artifacts. Based on this, a first registration process is performed on each initial cardiac imaging set to obtain cardiac images with very weak or completely eliminated artifacts. This magnetic resonance imaging method can effectively reduce artifacts in delayed contrast-enhanced cardiac imaging. Furthermore, since only the target phase mode is changed without adding additional scanning or acquisition processes, this embodiment is simple to implement and does not add extra operations or scanning time.

[0041] In one embodiment, please refer to Figure 5 Magnetic resonance imaging methods include S502 to S508.

[0042] S502, during the first cardiac cycle, the electrocardiogram characteristic signal of the detection object is identified. Then, after a preset delay time of the electrocardiogram characteristic signal, a first sequence pulse is applied to the detection object. After the inversion recovery time, a second sequence pulse of the target phase pattern is applied to the detection object to obtain an initial cardiac imaging set.

[0043] The first sequence of pulses is used to reverse the longitudinal magnetization vector of the target object. The target phase mode is one of at least two different phase modes, and the artifact positions in the initial cardiac imaging set corresponding to different target phase modes are different. The explanation of step S502 can be found above.

[0044] S504, in the second cardiac cycle following the first cardiac cycle, a third sequence of pulses with the same target phase pattern as the previous first cardiac cycle is applied to the target object to obtain a reference imaging set.

[0045] The second cardiac cycle refers to a cardiac cycle that follows and is adjacent to the first cardiac cycle. The third sequence pulse includes multiple second excitation pulses. Each reference image in the reference imaging set is generated under the excitation of its corresponding second excitation pulse. Applying a third sequence pulse with the same target phase mode as the previous first cardiac cycle to the detection object specifically means that if a second sequence pulse with the first phase mode as the target phase mode was applied in the first cardiac cycle, then a third sequence pulse with the first phase mode as the target phase mode is applied in the second cardiac cycle that follows and is adjacent to the first cardiac cycle.

[0046] Understandably, in cardiac delayed contrast-enhanced imaging, to avoid the complications of calculating the inversion recovery time or to eliminate the negative impact of inaccurate calculations, the approach of Phase Sensitive Inversion Recovery (PSIR) can be used. Please refer to [link to relevant documentation]. Figure 6 In the second cardiac cycle following the first cardiac cycle, a third sequence pulse with the same target phase pattern as the previous first cardiac cycle is applied. Since the reference imaging set and the initial cardiac imaging set are excited by the same target phase pattern, and the acquisition time of the reference imaging set is separated from the acquisition time of the initial cardiac imaging set by one cardiac cycle, the longitudinal magnetization vector of the normal myocardial signal has recovered to 0. The initial cardiac imaging set can be phase corrected using the reference imaging set without relying on calculating the accurate TI time to acquire a better imaging effect.

[0047] S506, Perform a first registration process on the initial cardiac image set obtained in each first cardiac cycle to obtain cardiac images, and perform a first registration process on the reference image set obtained in each second cardiac cycle to obtain phase reference images.

[0048] The reference image sets obtained in each second cardiac cycle also encounter the problems described in step S206. Therefore, a first registration process is performed on the reference image sets to obtain phase reference images with complete motion calibration and weak artifacts. Phase reference imaging can then be used for phase correction of cardiac imaging.

[0049] S508 uses phase reference imaging to perform a second registration process on the cardiac image to obtain the real part of the cardiac image.

[0050] It can be understood that cardiac imaging is a complex image, and the real part of the cardiac imaging is the image corresponding to the real part of this complex image. Since there may be motion offset issues between the phase reference imaging and the cardiac imaging as mentioned in step S206, the second registration process includes motion calibration between the phase reference imaging and the cardiac imaging. Furthermore, the second registration process also includes phase correction of the cardiac imaging using the phase reference imaging based on the phase-sensitive recovery approach, thereby extracting the real part of the complex image. When reconstructing magnetic resonance images using the real part of the cardiac imaging, the difference between abnormal and normal myocardium will be more pronounced. Phase correction of the cardiac imaging using the phase reference imaging based on the phase-sensitive recovery approach mainly utilizes the phase reference imaging as the background phase; subtracting the background phase from the cardiac imaging yields the real part of the cardiac imaging.

[0051] In one embodiment, the phase of the excitation pulse changes according to the phase pattern in such a way that the phase difference between adjacent excitation pulses is a fixed angle (i.e., phase step). Since the phase cycles in 360° increments, the phase of each excitation pulse changes cyclically according to a certain phase cycle structure. For example, the phase step is 180°. In the prior art, the phase of the first excitation pulse in the second sequence pulse changes cyclically in the manner of 0°, 180°, 0°, 180°... and the phase step of different second sequence pulses remains constant at 180°. Based on this, the phase step corresponding to different target phase patterns is set to be different. The step of applying a second sequence pulse of the target phase pattern to the detection object to obtain an initial cardiac imaging set includes: applying multiple first excitation pulses to the detection object, wherein the phase difference between each adjacent first excitation pulse is the same as the phase step corresponding to the target phase pattern; and obtaining the initial cardiac images corresponding to each first excitation pulse to obtain an initial cardiac imaging set. It is understandable that since the phase of the first excitation pulse will affect the position of artifacts in the initial cardiac imaging obtained based on the first excitation pulse, and the phase steps corresponding to different target phase modes are different, the first excitation pulses in the second sequence pulses with different target phase modes will undergo phase changes with different phase cycle structures, thereby causing the artifacts in the initial imaging set corresponding to the second sequence pulses of different target phase modes to all be shifted in position.

[0052] In one embodiment, the phase step corresponding to the target phase pattern is determined by the following steps: determining the step coefficient based on the number of times the second sequence pulses are applied; and obtaining the phase step corresponding to the target phase pattern based on the step coefficient and the preset phase step.

[0053] The number of times the second sequence pulse is applied refers to the nth time it is applied during the entire magnetic resonance imaging (MRI) scan. The phase step can be obtained by multiplying the step coefficient by the preset phase step. Therefore, different step coefficients for the target phase mode will result in different phase steps for the target phase mode. Assuming there are M selectable phase modes, there are M step coefficients. The approach adopted in this embodiment is to apply second sequence pulses with different target phase modes for each of the M consecutive first cardiac cycles, meaning the phase steps of the second sequence pulses for the M consecutive first cardiac cycles are all different. During the entire MRI scan, the phase mode of the second sequence pulse applied for the (i+M*k)th time (M≥i≥1, k≥0, where i and k are integers) is the same, meaning the second sequence pulse applied for the (i+M*k)th time has the same phase step. Therefore, based on the number of times the second sequence pulse is applied, it can be determined which of the M step coefficients should be used for the second sequence pulse.

[0054] In one embodiment, exemplary and not limiting, the preset phase step can be obtained based on 360° / M. For example, if the step factor is selected as the number of applications of the second sequence pulses - 1, and M is selected as 4, then the preset phase step is 90°. Please refer to [link to documentation]. Figure 7 There are four different target phase modes. The phase step of the second sequence pulse of the 1+4*kth iteration is (1+4*k-1)*90°, which simplifies to a phase step of 0° for all 1+4*kth iterations, with a phase cycle structure of 0°, 0°, 0°, 0°... Similarly, the phase step of the second sequence pulse of the 2+4*kth iteration is (2+4*k-1)*90°, which simplifies to a phase step of 90° for all 2+4*kth iterations, with a phase cycle structure of 0°, 90°, 180°, 270°... The phase step of the second sequence pulse of the 3+4*kth iteration is (3+4*k-1)*90°, which simplifies to a phase step of 180° for all 3+4*kth iterations, with a phase cycle structure of 0°, 180°, 0°, 180°... The phase step of the 4+4*kth second sequence pulse is (4+4*k-1)*90°. Simplifying, we know that the phase step of the 4+4*kth second sequence pulse is always 270°, and the phase cycle structure is 0°, 270°, 180°, 90°... For example, if M is selected as 2, the preset phase step is 180°. Please refer to... Figure 8There are two different target phase modes. The phase step of the 1+2*kth second sequence pulse is (1+2*k-1)*180°. Simplifying, the phase step of the 1+2*kth (odd-numbered) second sequence pulses is 0°, with a phase cycle structure of 0°, 0°, 0°, 0°... Similarly, the phase step of the 2+2*kth second sequence pulse is (2+2*k-1)*180°. Simplifying, the phase step of the 2+2*kth (even-numbered) second sequence pulses is 180°, with a phase cycle structure of 0°, 180°, 0°, 180°... It should be noted that, in this embodiment, the phase of the second sequence pulse represents the initial phase of the radio frequency pulses contained in the second sequence, which affects the rotational direction of the proton group within the detected object. In this embodiment, taking the three-dimensional coordinate system formed by X, Y and Z as an example, X and Y are perpendicular to the Z axis direction, 0° can correspond to the direction parallel to the X axis, and 90° can correspond to the direction parallel to the Y axis.

[0055] In one embodiment, please refer to Figure 9 The first registration process for the initial cardiac imaging set obtained in each first cardiac cycle includes steps S902 and S904.

[0056] S902: Select any one image from all initial cardiac images as the reference image, and register the remaining initial cardiac images with the reference image as the reference to obtain each registered initial cardiac image.

[0057] Registration involves deforming the image to be registered using a reference image, such as by translation, scaling, and / or rotation, to make the image to be registered similar to the reference image. Optionally, rigid body registration algorithms or non-rigid body registration algorithms can be used to register each initial cardiac image other than the reference image. Furthermore, since it is not necessary to register the reference image itself using the reference image, the final registered initial cardiac images also include the reference image.

[0058] S904, determine the first target pixel value of each pixel in the initial cardiac image of each registration, set the pixel value of the corresponding pixel in the cardiac image according to each first target pixel value, and obtain the cardiac image.

[0059] The first target pixel value includes the maximum pixel value of a pixel in each initial registered cardiac image, or the average or median pixel value in each initial registered cardiac image. This first target pixel value is used to supplement the final cardiac image with effective information that is not displayed due to artifacts in the initial registered cardiac images at different artifact locations, thus incorporating information that is affected by artifacts. Specifically, considering the low pixel value of artifacts, the maximum pixel value of each pixel in each initial registered cardiac image is extracted. The extracted pixel values ​​are contributed by pixels not corresponding to artifact regions. Then, the pixel values ​​of the corresponding pixels in the cardiac image are set according to the maximum pixel values. This allows the imaging results unaffected by artifact regions to be filled into the cardiac image, resulting in cardiac images with very weak or no artifact regions. Alternatively, since the artifact locations in each initial registered cardiac image are different, only a few images at the same location have artifacts, while the rest are normal images. Therefore, the influence of artifacts can be reduced by taking the average or median value.

[0060] Specifically, since the initial cardiac imaging for registration has undergone motion correction, if the position of a pixel in the initial cardiac imaging is represented by the number of rows and columns, then pixels with the same number of rows and columns should reflect the same position of the detected object in each initial cardiac imaging for registration. When setting the pixel value of the cardiac imaging, the pixels with the same number of rows and columns in the initial cardiac imaging for registration can be selected as the setting object based on the number of rows and columns of the pixel from which the first target pixel value is extracted. After setting all pixels in the cardiac imaging, the final cardiac imaging can be obtained. For example, in each initial cardiac imaging for registration, if the pixel value of the pixel in row b and column c of the a-th initial cardiac imaging for registration is larger than that of the pixels in row b and column c of the other initial cardiac imaging for registration, then the pixel value of the pixel in row b and column c of the a-th initial cardiac imaging for registration is selected as the first target pixel value of the pixel in row b and column c, and this first target pixel value is set as the pixel value of the pixel in row b and column c of the cardiac imaging.

[0061] In one embodiment, the first registration process for the reference image set obtained in each second cardiac cycle includes: selecting any one image from all reference images as a reference image, registering the remaining reference images with the reference image as a reference to obtain each registered reference image; determining a second target pixel value for each pixel in each registered reference image, and setting the pixel value of the corresponding pixel in the phase reference image according to each second target pixel value to obtain a phase reference image. The second target pixel value includes the maximum pixel value of the pixel in each registered reference image, or the average or median value of the pixel in each registered reference image. A description of this embodiment can be found above.

[0062] In one embodiment, the step of selecting a reference image from all initial cardiac images and registering the remaining initial cardiac images with the reference image as a reference to obtain each registered initial cardiac image includes: selecting a reference image from each average initial cardiac image corresponding to the same phase mode, and registering the remaining initial cardiac images corresponding to the same phase mode with the reference image as a reference to obtain each registered initial cardiac image.

[0063] Considering that initial cardiac images obtained based on the same target phase pattern are relatively similar and have a faster processing speed during motion correction, registration was performed separately for the initial cardiac images obtained from each target phase pattern. Figure 7 The following example illustrates four target phase modes: A first reference image is selected from the initial cardiac images corresponding to the 1+4*kth second sequence pulses, and the remaining initial cardiac images corresponding to the 1+4*kth second sequence pulses are calibrated based on the first reference image. A second reference image is selected from the initial cardiac images corresponding to the 2+4*kth second sequence pulses, and the remaining initial cardiac images corresponding to the 2+4*kth second sequence pulses are calibrated based on the second reference image. A third reference image is selected from the initial cardiac images corresponding to the 3+4*kth second sequence pulses, and the remaining initial cardiac images corresponding to the 3+4*kth second sequence pulses are calibrated based on the third reference image. A fourth reference image is selected from the initial cardiac images corresponding to the 4+4*kth second sequence pulses, and the remaining initial cardiac images corresponding to the 4+4*kth second sequence pulses are calibrated based on the fourth reference image. Figure 8 The following example illustrates two target phase modes: A fifth reference image is selected from each initial cardiac image corresponding to the 1+2*kth second sequence pulse, and the remaining initial cardiac images corresponding to the 1+2*kth second sequence pulse are calibrated based on the fifth reference image. A sixth reference image is selected from each initial cardiac image corresponding to the 2+2*kth second sequence pulse, and the remaining initial cardiac images corresponding to the 2+2*kth second sequence pulse are calibrated based on the sixth reference image. The method of selecting the reference image is not limited to the description in this embodiment; a reference image can be arbitrarily selected from all initial cardiac images. For example, the initial cardiac image corresponding to the first applied second sequence pulse can be selected as the reference image.

[0064] Similarly, in one embodiment, the step of selecting a reference image from all reference images and registering the remaining reference images with the reference image as a reference to obtain each registered reference image includes: selecting a reference image from each reference image corresponding to the same phase mode, and registering the remaining reference images corresponding to the same phase mode with the reference image as a reference to obtain each registered reference image.

[0065] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0066] Secondly, based on the same inventive concept, this application also provides a magnetic resonance imaging device for implementing the magnetic resonance imaging method described above. The solution provided by this device is similar to the solution described in the above method; therefore, the specific limitations of one or more magnetic resonance imaging device embodiments provided below can be found in the limitations of the magnetic resonance imaging method above, and will not be repeated here. The magnetic resonance imaging device includes a first pulse module, a second pulse module, and a first registration module. The first pulse module is used to identify the electrocardiogram (ECG) characteristic signal of the detection object during a first cardiac cycle, and then apply a first sequence pulse to the detection object after a preset delay time of the ECG characteristic signal. The first sequence pulse is used to reverse the longitudinal magnetization vector of the detection object. The second pulse module is used to apply a second sequence pulse of a target phase mode to the detection object after applying the first sequence pulse and after a reversal recovery time, to obtain an initial cardiac imaging set, wherein the target phase mode is one of at least two different phase modes, and the artifact positions in the initial cardiac imaging sets corresponding to different target phase modes are different. The first registration module is used to perform a first registration process on the initial cardiac imaging sets obtained in each first cardiac cycle to obtain cardiac images.

[0067] In one embodiment, the magnetic resonance imaging apparatus further includes a third pulse module and a second registration module. The third pulse module is used to apply a third sequence of pulses with the same target phase pattern as the previous first cardiac cycle to the target object during a second cardiac cycle following the first cardiac cycle, thereby obtaining a reference image set. The first registration module is further used to perform a first registration process on the reference image sets obtained in each second cardiac cycle to obtain a phase reference image. The second registration module is used to perform a second registration process on the cardiac image using the phase reference image to obtain a real part image of the heart.

[0068] In one embodiment, the first registration module includes a motion correction unit and a pixel value setting unit. The motion correction unit selects any one image from all initial cardiac images as a reference image, and registers the remaining initial cardiac images with the reference image as a reference to obtain each registered initial cardiac image. The pixel value setting unit determines a first target pixel value for each pixel in each registered initial cardiac image, and sets the pixel value of the corresponding pixel in the cardiac image according to each first target pixel value to obtain the cardiac image. The first target pixel value includes the maximum pixel value of the pixel in each registered initial cardiac image, or the average or median value of the pixel in each registered initial cardiac image.

[0069] In one embodiment, the motion correction unit is further configured to select any one image from all reference images as a reference image, and register the remaining reference images with the reference image as a reference to obtain each registered reference image. The pixel value setting unit is further configured to determine a second target pixel value for each pixel in each registered reference image, and set the pixel value of the corresponding pixel in the phase reference image according to each second target pixel value to obtain a phase reference image. The second target pixel value includes the maximum pixel value of the pixel in each registered reference image, or the average or median value of the pixel in each registered reference image.

[0070] In one embodiment, the motion correction unit is further configured to select a reference image from each initial cardiac image corresponding to the same phase mode, and register the remaining initial cardiac images corresponding to the same phase mode with the reference image as a reference to obtain each registered initial cardiac image.

[0071] In one embodiment, the motion correction unit is further configured to select a reference image from each reference image corresponding to the same phase mode, and register the remaining reference images corresponding to the same phase mode with the reference image as a reference to obtain each registered reference image.

[0072] Each module in the aforementioned magnetic resonance imaging device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in the processor of a computer device in hardware form or independent of it, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0073] Thirdly, embodiments of the present invention provide a magnetic resonance imaging device, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the aforementioned magnetic resonance imaging method. This magnetic resonance imaging device can be... Figure 1 The computer device 104 controls the magnetic resonance scanner 102 to apply pulses, or it can directly... Figure 1 The magnetic resonance scanner 102 in the middle. Using magnetic resonance imaging equipment as... Figure 1 Taking computer device 104 as an example, its internal structure diagram can be shown as follows: Figure 10 As shown, the computer device includes a processor, memory, communication interface, display screen, and input devices connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, mobile cellular networks, NFC (Near Field Communication), or other technologies. When the computer program is executed by the processor, it implements a magnetic resonance imaging method. The display screen can be an LCD screen or an e-ink screen. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad on the computer device's casing, or an external keyboard, touchpad, or mouse.

[0074] Those skilled in the art will understand that Figure 10 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0075] Fourthly, embodiments of the present invention provide a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the above-described magnetic resonance imaging method.

[0076] Fifthly, embodiments of the present invention provide a computer program product, including a computer program that, when executed by a processor, implements the steps of the above-described magnetic resonance imaging method.

[0077] 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, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties.

[0078] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, databases, 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 many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0079] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0080] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A magnetic resonance imaging method, characterized in that, include: During the first cardiac cycle, the electrocardiogram (ECG) characteristic signal of the detection object is identified. After a preset delay time following the identification of the ECG characteristic signal, a first sequence pulse is applied to the detection object. The first sequence pulse is used to reverse the longitudinal magnetization vector signal of the detection object. After applying the first sequence pulse, after an inversion recovery time, a second sequence pulse of the target phase pattern is applied to the detection object to obtain an initial cardiac imaging set, wherein the target phase pattern is one of at least two different phase patterns, and the positions of artifacts in the initial cardiac imaging set corresponding to different target phase patterns are different; The initial cardiac image set obtained in each of the first cardiac cycles is subjected to a first registration process to obtain cardiac images.

2. The magnetic resonance imaging method according to claim 1, characterized in that, The magnetic resonance imaging method further includes: In the second cardiac cycle following the first cardiac cycle, a third sequence of pulses of the same target phase pattern as in the previous first cardiac cycle is applied to the detected object to obtain a reference imaging set; The step of performing a first registration process on the initial cardiac image set obtained in each of the first cardiac cycles to obtain cardiac images further includes: The first registration process is performed on the reference image set obtained in each of the second cardiac cycles to obtain a phase reference image; The cardiac image is then registered using the phase reference imaging to obtain the real part of the cardiac image.

3. The magnetic resonance imaging method according to claim 1, characterized in that, The step of performing a first registration process on the initial cardiac imaging set obtained for each of the first cardiac cycles includes: From all the initial cardiac images, select any one image as the reference image, and register the remaining initial cardiac images with the reference image to obtain each registered initial cardiac image. A first target pixel value is determined for each pixel in each of the initial registered cardiac images. The pixel value of the corresponding pixel in the cardiac image is set according to each first target pixel value to obtain the cardiac image. The first target pixel value includes the maximum pixel value of the pixel in each of the initial registered cardiac images, or the average or median value of the pixel in each of the initial registered cardiac images.

4. The magnetic resonance imaging method according to claim 3, characterized in that, The step of selecting a reference image from all the initial cardiac images, and registering the remaining initial cardiac images with the reference image as a reference to obtain each registered initial cardiac image includes: The reference image is selected from each initial cardiac image corresponding to the same target phase mode. Using the reference image as a reference, the remaining initial cardiac images corresponding to the same target phase mode are registered to obtain each registered initial cardiac image.

5. The magnetic resonance imaging method according to claim 2, characterized in that, The step of performing the first registration process on the reference image set obtained in each of the second cardiac cycles to obtain a phase reference image includes: Select any one image from all the initial reference images as the reference image, and register the remaining reference images with the reference image as the reference to obtain each registered reference image; A second target pixel value is determined for each pixel in each of the registration reference images. The pixel value of the corresponding pixel in the phase reference image is set according to each second target pixel value to obtain the phase reference image. The second target pixel value includes the maximum pixel value of the pixel in each of the registration reference images, or the average or median value of the pixel in each of the registration reference images.

6. The magnetic resonance imaging method according to any one of claims 1-5, characterized in that, The second sequence pulse includes multiple first excitation pulses, and the phase steps corresponding to the different target phase modes are different. The step of applying the second sequence pulse of the target phase mode to the detection object to obtain the initial cardiac imaging set includes: Multiple first excitation pulses are applied to the detection object, and the phase difference between each adjacent first excitation pulse is the same as the phase step corresponding to the target phase pattern; The initial cardiac images corresponding to each of the first excitation pulses are obtained to obtain the initial cardiac image set.

7. The magnetic resonance imaging method according to any one of claims 1-5, characterized in that, The electrocardiogram (ECG) characteristic signals of the identified detection object include: Obtain the electrocardiogram trace of the detected object; Identify the R wave of the electrocardiogram trace, where the R wave is the characteristic signal of the electrocardiogram.

8. A magnetic resonance imaging device, characterized in that, The device includes: The first pulse module is used to identify the electrocardiogram characteristic signal of the detection object during the first cardiac cycle. Then, after a preset delay time of the electrocardiogram characteristic signal, a first sequence pulse is applied to the detection object. The first sequence pulse is used to reverse the longitudinal magnetization vector signal of the detection object. The second pulse module is used to apply a second sequence pulse of the target phase mode to the detection object after the first sequence pulse is applied and after the inversion recovery time, to obtain an initial cardiac imaging set, wherein the target phase mode is one of at least two different phase modes, and the artifact positions in the initial cardiac imaging set corresponding to different target phase modes are different. The first registration module is used to perform a first registration process on the initial cardiac image set obtained in each of the first cardiac cycles to obtain cardiac images.

9. A magnetic resonance imaging device, comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the magnetic resonance imaging method according to any one of claims 1 to 7.

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

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