Magnetic resonance imaging method, magnetic resonance scanning control method and magnetic resonance imaging system
By averaging multiple adjacent echo time images in the magnetic resonance imaging method, the signal-to-noise ratio reduction and image distortion problems caused by the long echo time in traditional diffusion imaging are solved, and the diffusion imaging effect with high signal-to-noise ratio and zero deformation is achieved.
Patent Information
- Application Number
- CN202311228636.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-21
- Publication Date
- 2025-03-21
AI Technical Summary
Traditional diffusion imaging has a long echo time, resulting in a decrease in the signal-to-noise ratio of the image, and is limited in the application of the skull base, forehead and other parts, making the image generation effect poor. In the prior art, forcibly merging and filling K-space data from different sources will produce image distortion and blurring effects.
In the magnetic resonance imaging method, the image signal-to-noise ratio is improved by using multiple adjacent echo time images to consider the echo time dimension during data reconstruction, ensuring that the signal of each image comes from the same echo time, thereby avoiding image distortion and blurring.
It achieves zero deformation in principle, improves the microstructure detection sensitivity and application range of diffusion imaging, improves the image signal-to-noise ratio, and avoids image distortion and blur.
Smart Images
Figure CN119667572A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of imaging technology, and in particular to a magnetic resonance imaging method, a magnetic resonance scanning control method and a magnetic resonance imaging system. Background Art
[0002] In the prior art, due to the introduction of diffusion magnetic field gradient, the echo time (TE) of traditional diffusion imaging is relatively long, resulting in a decrease in the image signal-to-noise ratio. At the same time, due to the influence of magnetic susceptibility deformation, its application in parts such as the skull base and forehead is limited, and the image generation effect is poor. Although there are solutions in the prior art to fill the K-space data to reconstruct the image and enhance the image signal-to-noise ratio, forcibly merging and filling the K-space data from different sources into the same K-space for reconstruction will produce image distortion and image blurring effects.
[0003] There is currently a lack of simple and effective technical solutions to solve the above problems. Summary of the invention
[0004] The object of the present invention is to provide a magnetic resonance imaging method, a magnetic resonance scanning control method and a magnetic resonance imaging system, which utilize the averaging of multiple adjacent echo time images to further improve the image signal-to-noise ratio, achieve zero deformation in principle, and improve the microstructure detection sensitivity and application range of diffusion imaging.
[0005] To achieve the above-mentioned purpose, the present invention provides a magnetic resonance imaging method, which includes: a single sampling step, specifically including: applying a radio frequency pulse to a scanned object; in a frequency encoding direction, in a preset time period, alternately applying a plurality of forward frequency encoding magnetic field gradients and reverse frequency encoding magnetic field gradients over time to determine a plurality of echo time points; in a phase encoding direction, in the same preset time period, applying a first phase encoding magnetic field gradient; corresponding to each of the echo time points, acquiring K space data of the echo time point; looping the single sampling step for multiple times to acquire a plurality of K space data corresponding to each of the echo time points; generating an echo image corresponding to each of the echo time points based on the plurality of K space data acquired at the same echo time point.
[0006] Optionally, applying a first phase encoding gradient in the phase encoding direction within the same preset time period specifically includes: applying a plurality of forward phase encoding magnetic field gradients and reverse phase encoding magnetic field gradients in the phase encoding direction within the same preset time period.
[0007] Optionally, the phase encoding magnetic field gradient is adjusted according to the initial phase of the hydrogen protons of the scanned object at the beginning of the preset time period so that the mapping coordinate point of the K-space image corresponding to the K-space data is as close as possible to the center of the K-space image.
[0008] Optionally, the multiple K-space data acquired at the same echo time point form a K-space data set, and the K-space data set is undersampled along the first phase encoding direction, and each single sampling step only collects a portion of the K-space data set along the first phase encoding direction.
[0009] Optionally, the method further includes: applying a second phase encoding magnetic field gradient in the layer selection direction within the same preset time period.
[0010] Optionally, the pulse includes an excitation pulse and a refocusing pulse, and the excitation pulse and the refocusing pulse are applied at different time points; before and after the refocusing pulse, a diffusion magnetic field gradient is applied in at least one of the layer selection direction, the frequency encoding direction and the phase encoding direction.
[0011] To achieve the above-mentioned purpose, the present invention also provides a magnetic resonance scanning control method, which includes: applying an excitation pulse and at least one refocusing pulse to the scanned object in sequence, and applying a first diffusion gradient and a second diffusion gradient before and after at least one of the refocusing pulses, respectively; in the frequency encoding direction, applying a plurality of forward frequency encoding magnetic field gradients and reverse frequency encoding magnetic field gradients alternately over time to obtain and determine a plurality of echo time points; obtaining a K-space data set corresponding to each of the echo time points, and the K-space data set is undersampled; restoring and reconstructing the K-space data set to generate an echo image corresponding to each of the echo time points.
[0012] Optionally, the first diffusion gradient and the second diffusion gradient are at least one of an oscillating trapezoidal wave, a sine wave, a cosine wave, a triangle wave, and a rectangular wave.
[0013] Optionally, the restoring and reconstructing the K-space dataset includes: using a compressed sensing method or a parallel reconstruction method to restore unfilled sites in the K-space dataset.
[0014] To achieve the above-mentioned purpose, the present invention also provides a magnetic resonance imaging system, which is applied to any of the magnetic resonance imaging methods described above, and includes: a transmitting module, which is used to apply radio frequency pulses to the scanned object; a magnetic field gradient applying module, which is used to apply a magnetic field gradient; an acquisition module, which is used to acquire K-space data; and a generation module, which is used to generate an echo image corresponding to each echo time point based on multiple K-space data acquired at the same echo time point.
[0015] The magnetic resonance imaging method, magnetic resonance scanning control method and magnetic resonance imaging system provided by the present invention have the following beneficial effects:
[0016] The present invention provides a magnetic resonance imaging method, which comprises: a single sampling step, specifically comprising: applying a radio frequency pulse to a scanned object; in a frequency encoding direction, in a preset time period, alternately applying a plurality of forward frequency encoding magnetic field gradients and reverse frequency encoding magnetic field gradients over time to obtain a plurality of echo time points; in a phase encoding direction, in the same preset time period, applying a first phase encoding magnetic field gradient; corresponding to each of the echo time points, obtaining K space data of the echo time point; looping the single sampling step for multiple times to obtain a plurality of K space data corresponding to each of the echo time points; generating an echo image corresponding to each of the echo time points according to the plurality of K space data obtained at the same echo time point.
[0017] With such a configuration, the present invention takes into account the echo time dimension during data reconstruction, and takes into account the difference in echo time during each data acquisition, so that the signal of each image obtained comes from the same echo time, and thus there is no image distortion and blurring effect. By averaging multiple adjacent echo time images, the image signal-to-noise ratio can be further improved, and zero deformation can be achieved in principle, thereby improving the microstructure detection sensitivity and application range of diffusion imaging.
[0018] The present invention also provides a magnetic resonance scanning control method, and since the magnetic resonance scanning control method and the magnetic resonance imaging method are based on the same inventive concept, the magnetic resonance scanning control method utilizes the average of multiple adjacent echo time images to further improve the image signal-to-noise ratio, achieve zero deformation in principle, and improve the microstructure detection sensitivity and application range of diffusion imaging.
[0019] The present invention also provides a magnetic resonance imaging system, which is used to perform any of the magnetic resonance imaging methods described above. Therefore, the magnetic resonance imaging system uses multiple adjacent echo time images to further improve the image signal-to-noise ratio, achieve zero deformation in principle, and improve the microstructure detection sensitivity and application range of diffusion imaging. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 A schematic diagram of a flow chart of a magnetic resonance imaging method provided by an embodiment of the present invention;
[0021] Figure 2 A schematic diagram of a gradient timing sequence provided for a first embodiment of the present invention;
[0022] Figure 3 A schematic diagram of a three-dimensional rectangular coordinate system with an echo time dimension added to the two-dimensional K space provided by an embodiment of the present invention;
[0023] Figure 4A schematic diagram of a two-dimensional coordinate system provided by an embodiment of the present invention, using different echo times as the horizontal coordinate and the Y-direction coordinate in the two-dimensional K-space image as the vertical coordinate;
[0024] Figure 5 A schematic diagram of a reconstructed two-dimensional coordinate system provided by an embodiment of the present invention, using different echo times as the horizontal coordinates and the Y-direction coordinate in the two-dimensional K-space image as the vertical coordinate;
[0025] Figure 6 A schematic diagram of a gradient timing sequence provided for a second embodiment of the present invention;
[0026] Figure 7 A schematic diagram of a gradient timing sequence provided by a third embodiment of the present invention;
[0027] Figure 8 A schematic diagram of a block structure of an electronic device provided by an embodiment of the present invention;
[0028] The accompanying drawings are denoted as follows:
[0029] 11-excitation pulse; 12-focusing pulse; 21-diffusion magnetic field gradient; 31-first phase encoding magnetic field gradient; 32-second phase encoding magnetic field gradient; 41-frequency encoding magnetic field gradient;
[0030] 101 - processor; 102 - communication interface; 103 - memory; 104 - communication bus; 105 - display. DETAILED DESCRIPTION
[0031] In order to make the purpose, advantages and features of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, the structure shown in the drawings is often a part of the actual structure. In particular, the emphasis of each drawing is different, and sometimes different scales are used.
[0032] It should be understood that when an element or layer is referred to as "on...", "connected to" other elements or layers, it can be directly on other elements or layers, connected to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on...", "directly connected to" other elements or layers, there is no intervening element or layer. Although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish an element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer or part discussed below can be expressed as a second element, component, region, layer or part. Spatial relationship terms such as "under...", "below", "below", "above...", "above", "above", etc., can be used here for the convenience of description to describe the relationship between an element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, the spatial relationship terms are intended to include different orientations of the devices in use and operation. For example, if the device in the accompanying drawings is turned over, then, the elements or features described as "under...", "below", "below" will be oriented to be "on" other elements or features. The device can be oriented in addition (rotated 90 degrees or other orientations) and the spatial descriptors used herein are interpreted accordingly. The purpose of the terms used herein is only to describe specific embodiments and is not intended to be a limitation of the present invention. When used herein, the singular forms of "one", "one" and "said / the" are also intended to include plural forms, unless the context clearly indicates another way. It should also be understood that the term "include" is used to determine the presence of features, steps, operations, elements and / or parts, but does not exclude the presence or addition of one or more other features, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.
[0033] The object of the present invention is to provide a magnetic resonance imaging method, a magnetic resonance scanning control method and a magnetic resonance imaging system, which utilize multiple adjacent echo time images to further improve the image signal-to-noise ratio, achieve zero deformation in principle, and improve the microstructure detection sensitivity and application range of diffusion imaging.
[0034] To achieve the above object, the present invention provides a magnetic resonance imaging method, please refer to Figure 1 , Figure 1 A schematic diagram of a magnetic resonance imaging method according to an embodiment of the present invention is shown in FIG. Figure 1 As shown, the method includes:
[0035] The single sampling steps include:
[0036] applying radio frequency pulses to the scanned object;
[0037] In the frequency encoding direction, a plurality of forward frequency encoding magnetic field gradients and reverse frequency encoding magnetic field gradients are applied alternately over time within a preset time period to determine a plurality of echo time points;
[0038] In the phase encoding direction, within the same preset time period, applying a first phase encoding magnetic field gradient;
[0039] Corresponding to each of the echo time points, acquiring K-space data of the echo time point;
[0040] The single sampling step is cycled for multiple times (a preset required number of times can be set when reflected in the flowchart, and a determination is made whether the required number of times is reached, otherwise the loop body is entered, and if yes, the loop is terminated) to obtain multiple K-space data corresponding to each echo time point;
[0041] An echo image corresponding to each echo time point is generated according to the multiple K-space data acquired at the same echo time point.
[0042] With such a configuration, the present invention takes into account the echo time dimension during data reconstruction, and takes into account the difference in echo time during each data acquisition, so that the signal of each image obtained comes from the same echo time, and thus there is no image distortion and blurring effect. By using multiple adjacent echo time images, the image signal-to-noise ratio is further improved, and zero deformation is achieved in principle, which improves the microstructure detection sensitivity and application range of diffusion imaging.
[0043] The technical principle of the present invention is described in detail below:
[0044] Please refer to Figure 2 , Figure 2 Schematic diagram of gradient timing provided by the first embodiment of the present invention. Figure 2 As shown, as can be understood by those skilled in the art, during the nuclear magnetic resonance imaging process, three directions need to be defined, namely, the layer selection direction Gz (for example, when the scanned object is a human body, the layer selection direction is the length direction of the human body), the phase encoding direction Gy, and the frequency encoding direction Gx. The layer selection direction Gx, the phase encoding direction Gy, and the frequency encoding direction Gx are orthogonal to each other, forming a three-dimensional rectangular coordinate system in the real space. Nuclear magnetic resonance imaging requires applying radio frequency pulses to the scanned object, and the radio frequency pulses include an excitation pulse 11 (generally a 90-degree pulse) and a refocusing pulse 12 (generally a 180-degree pulse) applied successively, and the excitation pulse 11 and the refocusing pulse 12 are applied at different time points.
[0045] Based on the principle of echo planar imaging (EPI) technology, a frequency encoding gradient 41 can be applied in the frequency encoding direction within a preset time period. Specifically, a number of forward frequency encoding magnetic field gradients and reverse frequency encoding magnetic field gradients can be applied alternately over time. At this time, the forward frequency encoding magnetic field gradient and the reverse frequency encoding magnetic field gradient have opposite effects on the spins of hydrogen protons in the scanned object, which is reflected in Figure 2 It can be seen from the gradient timing diagram shown that the forward frequency-encoded magnetic field gradient will form a first integral located above the time axis over time, and the reverse frequency-encoded magnetic field gradient will form a second integral located below the time axis over time. The first integral and the second integral will inevitably cancel each other out at a certain moment, so that at this moment, the hydrogen protons of the scanned object are equivalent to not being applied with the frequency-encoded gradient 41. This moment can be called the echo time point. In summary, it can be concluded that by applying a number of forward frequency-encoded magnetic field gradients and reverse frequency-encoded magnetic field gradients alternately over time, a plurality of the echo time points can be obtained. In particular, when applying Figure 2 When the forward frequency encoding magnetic field gradient and the reverse frequency encoding magnetic field gradient are regularly alternating, multiple echo time points can be obtained. In this embodiment, each midpoint of the forward frequency encoding magnetic field gradient and the reverse frequency encoding magnetic field gradient is an echo time point, and the echo time point has a set time interval with the midpoint of the pulse (excitation pulse 11 in the figure) that generates the macroscopic transverse magnetization vector.
[0046] On this basis, in the phase encoding direction, within the same preset time period, applying the first phase encoding magnetic field gradient 31 will be able to affect the phase of the spin of the hydrogen protons of the scanned object, so as to achieve the acquisition of corresponding K space data at each of the callback time points for inverse Fourier transform. After the single sampling step is cycled multiple times, sufficient K space data for image reconstruction will be obtained. The first phase encoding magnetic field gradient 31 includes a plurality of preset gradient blips with different polarities, and the gradient distance (gradient area) of each preset gradient blip is set differently. In this embodiment, the polarities of two adjacent preset gradient blips can be set to be the same, but the gradient distances are different; or, the polarities of two adjacent preset gradient blips are opposite, and the gradient distances are different.
[0047] It can be seen that the present invention takes the echo time dimension into consideration when reconstructing data. For ease of understanding, please refer to Figure 3 , Figure 3 A schematic diagram of a three-dimensional rectangular coordinate system with an echo time dimension added to the two-dimensional K space provided by an embodiment of the present invention. Figure 3As shown, the kx axis of the three-dimensional rectangular coordinate system means the abscissa axis of the two-dimensional K-space image in the X direction, and the ky axis means the ordinate axis of the two-dimensional K-space image in the Y direction. To simulate the time dimension based on this, the echo time TE is used as the third coordinate axis to establish the following Figure 3 The three-dimensional rectangular coordinate system shown in Figure 1 is shown in Figure 1. On this basis, for further understanding, please refer to Figure 4 , Figure 4 A schematic diagram of a two-dimensional coordinate system provided by an embodiment of the present invention is provided, which is established by using different echo times as the abscissa and the Y-direction coordinate in the two-dimensional K-space image as the ordinate. Figure 4 Essentially, Figure 3 Ignoring the kx axis for now, the two-dimensional rectangular coordinate system can be considered as Figure 3 A side view of the three-dimensional rectangular coordinate system in . Figure 4 As shown in Figure 2, since the echo time TE is discrete, Figure 4 The echo time points of the horizontal axis in should be discrete, and in the process of multiple cycle scanning, multiple K-space data at the same echo time point will be obtained.
[0048] For each echo time point, the multiple K-space data acquired form a K-space data set ( Figure 4 The K-space dataset is undersampled along the first phase encoding direction (ky axis in the figure), and each single sampling step only collects the portion of the K-space dataset along the first phase encoding direction, that is, the data collected by each single sampling step only fills the portion of the K-space dataset, and the data collected by multiple single sampling steps are filled in sequence along the first phase encoding direction. Each column can correspond to a K-space image, so that one echo image can be generated accordingly, and multiple columns can generate multiple echo images.
[0049] Optionally, the filling of the K-space dataset is under-sampled, and its filling trajectory may be irregular. A compressed sensing method or a parallel reconstruction method may be used to restore the unfilled sites in the K-space dataset. Figure 5 As shown in the following example, Figure 4 The K-space data sets at different echo time points are shown, and the target K-space data sets are obtained after data recovery.
[0050] In this embodiment, because Figure 2 As shown, the polarities of two adjacent preset gradient peaks are the same, but the gradient distances are different; or, the polarities of two adjacent preset gradient peaks are opposite, and the gradient distances are different. Figure 4As shown in FIG. 1 , the filling trajectories (patterns composed of solid points in the figure) of the K-space data sets corresponding to two adjacent echo time points are different. In this way, the K-space data sets of adjacent echo time points can be reused or referenced during the recovery process of the K-space data set of any echo time point, which is conducive to improving the accuracy of data set recovery.
[0051] Optionally, multiple echo images may be weighted to obtain a target image, in which any pixel point of the target image is obtained by weighted averaging of pixel values of corresponding pixels in the multiple echo images, so that the target image has a higher contrast and signal-to-noise ratio.
[0052] In practical applications, the multiple echo images can be further used to generate an optimized echo image. Specifically, the method further includes: sorting the echo time points in chronological order, obtaining the echo images corresponding to the echo time points with the first preset number of digits; obtaining the optimized echo image according to the echo images with the first preset number of digits. The reason for selecting the echo images with the first preset number of digits in time ranking is that as the echo time points are farther and farther away from the initial time, image attenuation is inevitable. Therefore, selecting the first few echo images to generate the optimized echo image can improve the signal-to-noise ratio of the image finally generated. The generation method of the optimized echo image includes but is not limited to superimposing multiple echo images or averaging multiple echo images to generate, which will not be repeated here.
[0053] Figure 4 The reason why the horizontal coordinate of each echo time point corresponds to the mapping coordinate points of multiple different vertical coordinates is that in different scanning processes, the first phase encoding gradient has different degrees of influence on hydrogen protons. This influence is related to the application method of the first phase encoding gradient. Specifically, in the phase encoding direction, within the same preset time period, the first phase encoding gradient is applied, specifically including: in the phase encoding direction, within the same preset time period, a number of forward phase encoding magnetic field gradients and reverse phase encoding magnetic field gradients (which can be continuous or discrete) are applied. As reflected in the following Figure 2 In the gradient timing diagram shown, the forward phase encoding magnetic field gradient will form a third integral located above the time axis over time, and the reverse phase encoding magnetic field gradient will form a fourth integral located below the time axis over time. Different phase encoding magnetic field gradients and different frequency encoding magnetic field gradients will comprehensively affect the spin of hydrogen protons, thereby generating different K-space data, which are reflected in the K-space image as the mapping coordinate points of different K-space images. With this arrangement, the coordinates of different K-space images can be obtained as much as possible in multiple scans.
[0054] Preferably, the phase encoding magnetic field gradient can be adjusted according to the initial phase of the hydrogen protons of the scanned object at the beginning of the preset time period, so that the mapping coordinate point of the K-space image corresponding to the K-space data is as close as possible to the center of the K-space image. Such a setting helps to improve the signal-to-noise ratio of the image finally generated.
[0055] Furthermore, the acquisition of the echo image corresponding to each echo time point based on the multiple K-space data acquired at the same echo time point specifically includes: establishing a mapping coordinate point of the K-space image one-to-one according to each K-space data, arbitrarily selecting two adjacent mapping coordinate points, and determining the numerical range of the magnetic resonance parameter according to the two mapping coordinate points; and reconstructing the K-space data corresponding to the coordinate point between the two mapping coordinate points according to the numerical range. Please refer to the technical principle of this part of the solution Figure 4 and Figure 5 , Figure 5 A schematic diagram of a reconstructed two-dimensional coordinate system provided by an embodiment of the present invention using different echo times as the horizontal coordinate and the Y direction coordinate in the two-dimensional K-space image as the vertical coordinate. Figure 4 It can be seen that the mapping coordinate points of the K-space image at each echo time point obtained after multiple scans are still discrete, so the corresponding image data is not comprehensive enough. In order to restore the corresponding echo image more clearly, the coordinate points between the discrete mapping coordinate points should be restored and reconstructed. Each magnetic resonance parameter has a corresponding specific range. Based on the calculation, the signal attenuation in the corresponding range can be obtained, so that a database can be established as a priori data. After the numerical range of the magnetic resonance parameter is determined according to the prior law, the corresponding K-space data is obtained from the prior data, and reconstructed by interpolation or the principle of corresponding range selection. The prior law can be obtained through experiments or experience. For example, when scanning the human brain, it can be confirmed that the minimum transverse relaxation time will not be less than 0ms and the maximum will not exceed 5000ms. Then the range of the transverse relaxation time is [0,5000]ms, and this range can be the experimental or empirical range. Specifically, the relevant calculation can be based on the Bloch equation, and the relationship is as follows:
[0056]
[0057] Where:
[0058] M is the unit volume magnetization vector, which is determined by the relevant characteristics of the type of scanned object;
[0059] t is time;
[0060] γ is the gyromagnetic ratio, which is a constant;
[0061] B is the magnetic field strength;
[0062] M xy is the lateral component of M, which is the available data;
[0063] M z is the longitudinal component of M, which can be based on M xy Calculate acquisition;
[0064] is the M in the resting state z , can be based on M xy Calculate acquisition;
[0065] T2 and T1 are the transverse relaxation time and longitudinal relaxation time, respectively, which can be obtained based on magnetic resonance experimental scanning;
[0066] Based on the above principles and relations, the coordinate points between the discrete mapping coordinate points can be restored and reconstructed, thereby achieving Figure 4 Generate as Figure 5 The data shown can obtain a clearer and more comprehensive echo image.
[0067] Please continue to refer to Figure 2 Preferably, the pulse includes an excitation pulse 11 and a refocusing pulse 12, and the excitation pulse 11 and the refocusing pulse 12 are applied at different time points; before and after the refocusing pulse 12, a diffusion magnetic field gradient 21 is applied in at least one of the layer selection direction, the frequency encoding direction and the phase encoding direction. Figure 2 As shown, a pair of trapezoidal diffuse magnetic field gradients 21 are applied before and after the focusing pulse. Adjusting the gradient module time interval can change the diffusion time of water molecules, and adjusting the trapezoidal area can change the diffuse magnetic field gradient b value. It should be understood that the diffuse magnetic field gradient 21 can be applied in a variety of ways. In practice, there can be a variety of diffusion methods, such as sine or cosine modulated oscillating trapezoidal gradients, sine waves, cosine waves, triangle waves, arbitrary waveforms, etc. For details, please refer to Figure 6 , Figure 6 FIG. 1 is a schematic diagram of a gradient timing sequence provided by the second embodiment of the present invention. Figure 6 As shown, Figure 6 The diffuse magnetic field gradient 21 is a cosine modulated oscillating trapezoidal gradient.
[0068] Please refer to Figure 7 , Figure 7 It should be understood that the above description is based on two-dimensional imaging, and the present invention can also achieve three-dimensional imaging. Based on this, the present invention provides the following technical solutions: Figure 7 As shown, in the slice selection direction, within the same preset time period, a second phase encoding magnetic field gradient 32 is applied.
[0069] Please continue to refer to Figure 2, Figure 6 and Figure 7 ,pass Figure 2 , Figure 6 and Figure 7 We can find that the present invention applies two diffusion magnetic field gradients 21 before and after the refocusing pulse. To achieve diffusion imaging, two diffusion magnetic field gradients 21 can be applied before and after the refocusing pulse. Adjusting the module time interval of the diffusion magnetic field gradient 21 can change the diffusion time of water molecules. Adjusting the area of the diffusion magnetic field gradient 21 can change the diffusion gradient b value. Based on this, the present invention also provides a magnetic resonance scanning control method, which includes:
[0070] applying an excitation pulse and at least one focusing pulse to the scanned object in sequence, wherein a first diffusion gradient and a second diffusion gradient are applied before and after the at least one focusing pulse respectively;
[0071] In the frequency encoding direction, a plurality of forward frequency encoding magnetic field gradients and reverse frequency encoding magnetic field gradients are applied alternately over time to obtain and determine a plurality of echo time points;
[0072] Acquire a K-space data set corresponding to each of the echo time points, wherein the K-space data set is undersampled;
[0073] The K-space data set is restored and reconstructed to generate an echo image corresponding to each echo time point.
[0074] It should be understood that the first diffusion gradient and the second diffusion gradient can be at least one of an oscillating trapezoidal wave, a sine wave, a cosine wave, a triangle wave, and a rectangular wave.
[0075] Furthermore, the restoring and reconstructing the K-space dataset includes: restoring the unfilled sites in the K-space dataset using a compressed sensing method or a parallel reconstruction method. Such a setting can realize the restoration and reconstruction of the undersampled image.
[0076] To achieve the above object, the present invention further provides a magnetic resonance imaging system, which is applied to any of the above magnetic resonance imaging methods, comprising:
[0077] A transmitting module, used for applying radio frequency pulses to the scanned object;
[0078] A magnetic field gradient applying module, used for applying a magnetic field gradient;
[0079] An acquisition module, used for acquiring K-space data;
[0080] A generating module is used to generate an echo image corresponding to each echo time point according to a plurality of K-space data acquired at the same echo time point.
[0081] Since the magnetic resonance imaging system provided by the present invention and the magnetic resonance imaging method described above belong to the same inventive concept, the magnetic resonance imaging system provided by the present invention has all the advantages of the magnetic resonance imaging method described above, so the beneficial effects of the magnetic resonance imaging system provided by the present invention will not be described one by one here. Since the magnetic resonance imaging system is used to perform any of the magnetic resonance imaging methods described above. Therefore, the magnetic resonance imaging system uses multiple adjacent echo time images to further improve the image signal-to-noise ratio, achieve zero deformation in principle, and improve the microstructure detection sensitivity and application range of diffusion imaging.
[0082] Please refer to Figure 8 , Figure 8 The present invention further provides an electronic device, the electronic device comprising:
[0083] A memory 103 storing a computer program;
[0084] A processor 101 is connected to the memory for performing any one of the above-mentioned magnetic resonance imaging methods when calling the computer program;
[0085] The display 105 is communicatively connected with the processor and the memory, and is used to display a GUI interaction interface related to the magnetic resonance imaging method.
[0086] Since the electronic device provided by the present invention and the magnetic resonance imaging method described above belong to the same inventive concept, the electronic device provided by the present invention has all the advantages of the magnetic resonance imaging method described above, so the beneficial effects of the electronic device provided by the present invention will not be described one by one here. Since the electronic device is used to perform any of the magnetic resonance imaging methods described above. Therefore, the electronic device uses multiple adjacent echo time images to further improve the image signal-to-noise ratio, achieve zero deformation in principle, and improve the microstructure detection sensitivity and application range of diffusion imaging.
[0087] like Figure 8As shown, the electronic device also includes a communication interface 102 and a communication bus 104, wherein the processor 101, the communication interface 102, and the memory 103 communicate with each other through the communication bus 104. The communication bus 104 can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. The communication bus 104 can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, only one thick line is used in the figure, but it does not mean that there is only one bus or one type of bus. The communication interface 102 is used for communication between the above-mentioned electronic device and other devices.
[0088] The processor 101 referred to in the present invention may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc. The processor 101 is the control center of the electronic device, and various interfaces and lines are used to connect various parts of the entire electronic device.
[0089] The memory 103 may be used to store the computer program. The processor 101 implements various functions of the electronic device by running or executing the computer program stored in the memory 103 and calling the data stored in the memory 103 .
[0090] The memory 103 may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).
[0091] To achieve the above-mentioned purpose, the present invention provides a readable storage medium storing a computer program, which, when executed by a processor, implements a magnetic resonance imaging method as described in any one of the above. Since the readable storage medium provided by the present invention and the magnetic resonance imaging method described above belong to the same inventive concept, the readable storage medium provided by the present invention has all the advantages of the magnetic resonance imaging method described above, so the beneficial effects of the readable storage medium provided by the present invention will not be described one by one here. Since the readable storage medium is used to execute any of the magnetic resonance imaging methods described above. Therefore, the readable storage medium uses multiple adjacent echo time images to further improve the image signal-to-noise ratio, achieve zero deformation in principle, and improve the microstructure detection sensitivity and application range of diffusion imaging.
[0092] The readable storage medium of the embodiment of the present invention can adopt any combination of one or more computer-readable media. The readable medium can be a computer-readable signal medium or a computer-readable storage medium. The computer-readable storage medium can be, for example, but not limited to, a system, device or device of electricity, magnetism, light, electromagnetic, infrared or semiconductor, or any combination of the above. More specific examples (non-exhaustive list) of computer-readable storage media include: an electrical connection with one or more wires, a portable computer hard disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In this article, a computer-readable storage medium can be any tangible medium containing or storing a program, which can be used by an instruction execution system, a device or a device or used in combination with it.
[0093] Computer-readable signal media may include data signals propagated in baseband or as part of a carrier wave, which carry computer-readable program codes. Such propagated data signals may take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. Computer-readable signal media may also be any computer-readable medium other than a computer-readable storage medium, which may send, propagate, or transmit a program for use by or in conjunction with an instruction execution system, device, or device. The program code contained on the computer-readable medium may be transmitted using any suitable medium, including but not limited to wireless, wire, optical cable, RF, etc., or any suitable combination of the above.
[0094] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description.
[0095] It should also be noted that, although the present invention has been disclosed as a preferred embodiment, the above embodiment is not intended to limit the present invention. For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.
[0096] It should also be understood that, unless otherwise specified or indicated, the terms "first", "second", "third", etc. in the specification are merely used to distinguish between the various components, elements, steps, etc. in the specification, and are not used to indicate the logical relationship or sequential relationship between the various components, elements, steps, etc.
[0097] It should also be recognized that the terms described herein are used only to describe specific embodiments and are not intended to limit the scope of the invention. It should be noted that the singular forms "a" and "an" used herein and in the appended claims include plural references unless the context clearly indicates otherwise. For example, a reference to "a step" or "a device" means a reference to one or more steps or devices, and may include secondary steps and secondary devices. All conjunctions used should be understood in the broadest sense. And, the word "or" should be understood to have the definition of a logical "or", rather than a logical "exclusive or", unless the context clearly indicates otherwise. In addition, the implementation of embodiments of the present invention may include performing selected tasks manually, automatically, or in combination.
Claims
1. A magnetic resonance imaging method, characterized in that: The method comprises: The single sampling steps include: applying radio frequency pulses to the scanned object; In the frequency encoding direction, a plurality of forward frequency encoding magnetic field gradients and reverse frequency encoding magnetic field gradients are applied alternately over time within a preset time period to determine a plurality of echo time points; In the phase encoding direction, within the same preset time period, applying a first phase encoding magnetic field gradient; Corresponding to each of the echo time points, acquiring K-space data of the echo time point; The single sampling step is repeated multiple times to obtain a plurality of K-space data corresponding to each echo time point; An echo image corresponding to each echo time point is generated according to the multiple K-space data acquired at the same echo time point.
2. The magnetic resonance imaging method according to claim 1, wherein: The applying a first phase encoding gradient in the phase encoding direction within the same preset time period specifically includes: In the phase encoding direction, a plurality of forward phase encoding magnetic field gradients and reverse phase encoding magnetic field gradients are applied within the same preset time period.
3. The magnetic resonance imaging method according to claim 1, characterized in that: According to the initial phase of the hydrogen protons of the scanned object at the beginning of the preset time period, the first phase encoding magnetic field gradient is adjusted so that the filling site of the K-space data is located at the center of the K-space.
4. The magnetic resonance imaging method according to any one of claims 1 to 3, characterized in that: The multiple K-space data acquired at the same echo time point form a K-space data set, and the K-space data set is undersampled along the first phase encoding direction. Each single sampling step only collects a portion of the K-space data set along the first phase encoding direction.
5. The magnetic resonance imaging method according to any one of claims 1 to 3, characterized in that: The method further comprises: In the slice selection direction, a second phase encoding magnetic field gradient is applied within the same preset time period.
6. The magnetic resonance imaging method according to any one of claims 1 to 3, characterized in that: The pulses include an excitation pulse and a refocusing pulse, and the excitation pulse and the refocusing pulse are applied at different time points; Before and after the focusing pulse, a diffusion magnetic field gradient is applied in at least one of the slice selection direction, the frequency encoding direction and the phase encoding direction.
7. A magnetic resonance scanning control method, characterized in that: The method comprises: applying an excitation pulse and at least one focusing pulse to the scanned object in sequence, wherein a first diffusion gradient and a second diffusion gradient are applied before and after the at least one focusing pulse respectively; In the frequency encoding direction, a plurality of forward frequency encoding magnetic field gradients and reverse frequency encoding magnetic field gradients are applied alternately over time to obtain and determine a plurality of echo time points; Acquire a K-space data set corresponding to each of the echo time points, wherein the K-space data set is undersampled; The K-space data set is restored and reconstructed to generate an echo image corresponding to each echo time point.
8. The magnetic resonance scanning control method according to claim 7, characterized in that: The first diffusion gradient and the second diffusion gradient are at least one of an oscillating trapezoidal wave, a sine wave, a cosine wave, a triangle wave, and a rectangular wave.
9. The magnetic resonance scanning control method according to claim 7, characterized in that: The restoring and reconstructing the K-space data set includes: A compressed sensing method or a parallel reconstruction method is used to restore the unfilled sites in the K-space data set.
10. A magnetic resonance imaging system, characterized in that: A magnetic resonance imaging method as claimed in any one of claims 1 to 7, comprising: A transmitting module, used for applying radio frequency pulses to the scanned object; A magnetic field gradient applying module, used for applying a magnetic field gradient; An acquisition module, used for acquiring K-space data; A generating module is used to generate an echo image corresponding to each echo time point according to a plurality of K-space data acquired at the same echo time point.