Ultra-low field magnetic resonance imaging method, system, electronic equipment and product

Abstract

The present invention belongs to the field of magnetic resonance imaging technology, and its purpose is to provide an ultra-low field magnetic resonance imaging method, system, electronic equipment and product. The present invention reads out the area of ​​the pre-phase gradient Grp and the gradient delay of the readout gradient Gr for each gradient axis of different spokes in an iterative manner, so that the delay difference of the gradients of the two gradient axes read out by the radial acquisition method is as small as possible, and the center of the k space is aligned as much as possible to reduce the offset, so as to reduce the influence caused by the difference in gradient performance, thereby improving the image quality; at the same time, the present invention improves the imaging sequence, and by correcting the fast spin echo sequence, a better imaging effect can be obtained in the ultra-low field, so that the average number can be set to 1 at least, so that denser spokes can be collected, and two cycles are not required while improving the resolution, thereby shortening the scanning time under the premise of ensuring that the image resolution and quality meet the requirements.

Description

Technical Field

[0001] The present invention belongs to the technical field of magnetic resonance imaging, and in particular relates to an ultra-low field magnetic resonance imaging method, system, electronic equipment and product. Background Art

[0002] Magnetic resonance imaging technology is a diagnostic technology that uses the nuclear magnetic resonance phenomenon of certain atomic nuclei in the object to be tested (such as human tissue) and processes the resulting magnetic resonance signals through an electronic computer to reconstruct an image of a certain layer of the human body. At present, in the application of nuclear magnetic resonance imaging technology, ultra-low field magnetic resonance imaging is widely used in scenarios that require economical and efficient medical solutions, imaging of special populations, safe use of contrast agents, and portable medical equipment due to its advantages such as low cost, high safety, strong portability, and low shielding requirements.

[0003] Due to limitations such as low magnetic field strength and environmental interference, the uniformity of the main magnetic field (B0) is usually poor when performing ultra-low field magnetic resonance imaging on the object to be measured, which will affect the quality of the final generated image. For this reason, in the prior art, fast spin echo sequences are usually used to obtain better quality images. At the same time, when performing ultra-low field magnetic resonance imaging data acquisition, the Radial acquisition method (a non-Cartesian coordinate sampling method that obtains k-space data through radial trajectories) is also combined to increase insensitivity to motion, so as to reduce artifacts in the image caused by the motion of the object to be measured.

[0004] However, in the process of using the prior art, the inventors found that the prior art has at least the following problems:

[0005] When using the Radial acquisition method, the readout gradient will change with the rotation angle of the spokes, and the gradient performance (such as gradient delay and residual magnetization) under different gradient axes and different polarities of the same gradient axis will be different, resulting in poor data acquisition and imaging effects using the Radial sequence in ultra-low field MRI. In addition, conventional spin echo sequences usually use CPMG (Carr-Purcell-Meiboom-Gill, a pulse sequence) conditions to reduce artifacts caused by ringing and FID (Free Induction Decay), and at least two averages are required to achieve the ideal imaging effect, resulting in a longer scan time. Summary of the invention

[0006] The present invention aims to solve the above technical problems at least to a certain extent. The present invention provides an ultra-low field magnetic resonance imaging method, system, electronic equipment and product.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides an ultra-low field magnetic resonance imaging method, comprising:

[0009] A specified fast spin echo sequence is used to pre-scan the object to be measured; wherein, when the object to be measured is pre-scanned, the layer coding gradient and the layer coding gradient rewind gradient are not turned on;

[0010] Acquire a plurality of echo signals of each gradient axis generated by the object to be measured, and obtain a plurality of echo spoke images corresponding to the plurality of echo signals one by one according to the plurality of echo signals of each gradient axis;

[0011] Acquire a first echo spoke image and a second echo spoke image of each gradient axis from a plurality of echo spoke images of each gradient axis, and obtain an area compensation amount of a readout pre-phasing gradient and a gradient delay compensation amount of a readout gradient of each gradient axis according to the first echo spoke image and the second echo spoke image of each gradient axis;

[0012] Correcting the designated fast spin echo sequence according to the area compensation amount of the readout pre-phasing gradient and the gradient delay compensation amount of the readout gradient of each gradient axis to obtain a corrected fast spin echo sequence;

[0013] The modified fast spin echo sequence is used as a new designated fast spin echo sequence, so as to re-use the designated fast spin echo sequence to pre-scan the object to be measured, until the area compensation amount of the readout pre-dephasing gradient and the gradient delay compensation amount of the readout gradient of each gradient axis are both lower than a preset threshold value, and the obtained modified fast spin echo sequence is used as a final fast spin echo sequence;

[0014] The object to be measured is scanned by using the final fast spin echo sequence to obtain a magnetic resonance image of the object to be measured; wherein, when the object to be measured is scanned by using the final fast spin echo sequence, the layer coding gradient and the layer coding gradient rewind gradient are turned on.

[0015] In a possible design, the designated fast spin echo sequence adopts a 3D-FSE sequence, and the ETL direction of the designated fast spin echo sequence is a layer encoding direction.

[0016] In a possible design, when a predetermined fast spin echo sequence is used to pre-scan the object to be measured, two different phase cycle sequences are applied to two adjacent spokes.

[0017] In a possible design, a radial acquisition method is used to acquire multiple echo signals generated by the object to be measured, and the amplitude of the readout pre-phasing gradient is consistent with the amplitude of the readout gradient.

[0018] In a possible design, the area compensation amount of the readout pre-phase gradient of any gradient axis includes a positive area compensation amount and a negative area compensation amount, and the gradient delay compensation amount of the readout gradient of any gradient axis includes a positive gradient delay compensation amount and a negative gradient delay compensation amount; when any gradient axis is the X axis, its positive area compensation amount is:

[0019] ;

[0020] In the formula, is the image resolution of +X axis; N is the total number of readout points in +X direction; is the phase operation function; Read point for +X direction n The corresponding first echo spoke image, n=1,2,3,…,N-1 ; Read point for +X direction n the corresponding second echo spoke image;

[0021] When any of the gradient axes is the X axis, the positive gradient delay compensation amount is:

[0022] ;

[0023] In the formula, is the readout point sampling interval in the +X direction.

[0024] In a possible design, the specified fast spin echo sequence is corrected according to the area compensation amount of the readout pre-phasing gradient and the gradient delay compensation amount of the readout gradient of each gradient axis to obtain a corrected fast spin echo sequence, including:

[0025] Acquiring a spoke rotation angle in the specified fast spin echo sequence;

[0026] Obtaining a corrected readout prephasing gradient and a corrected gradient delay compensation amount for each gradient axis according to the spoke rotation angle in the specified fast spin echo sequence, an area compensation amount of a readout prephasing gradient for each gradient axis, and a gradient delay compensation amount of a readout gradient;

[0027] The designated fast spin echo sequence is corrected according to the corrected readout pre-phasing gradient and the corrected gradient delay compensation amount of each gradient axis to obtain a corrected fast spin echo sequence.

[0028] In a possible design, the specified fast spin echo sequence is corrected according to the corrected readout pre-phasing gradient and the corrected gradient delay compensation amount of each gradient axis to obtain a corrected fast spin echo sequence, including:

[0029] Performing an initial correction on the designated fast spin echo sequence according to the corrected readout pre-phasing gradient and the corrected gradient delay compensation amount of each gradient axis to obtain an initial corrected fast spin echo sequence;

[0030] The initial corrected fast spin echo sequence is corrected twice to obtain a corrected fast spin echo sequence.

[0031] In a second aspect, the present invention provides an ultra-low field magnetic resonance imaging system for implementing the ultra-low field magnetic resonance imaging method as described in any one of the above; the ultra-low field magnetic resonance imaging system comprises:

[0032] A magnetic resonance sequence correction module, used for pre-scanning the object to be measured by using a specified fast spin echo sequence; wherein, when the object to be measured is pre-scanned, the layer coding gradient and the layer coding gradient rewinding gradient are not turned on;

[0033] The magnetic resonance sequence correction module is further used to obtain a plurality of echo signals of each gradient axis generated by the object to be measured, and obtain a plurality of echo spoke images corresponding to the plurality of echo signals one by one according to the plurality of echo signals of each gradient axis;

[0034] The magnetic resonance sequence correction module is further used to respectively obtain a first echo spoke image and a second echo spoke image of each gradient axis from a plurality of echo spoke images of each gradient axis, and obtain an area compensation amount of a readout pre-phasing gradient and a gradient delay compensation amount of a readout gradient of each gradient axis according to the first echo spoke image and the second echo spoke image of each gradient axis;

[0035] The magnetic resonance sequence correction module is further used to correct the specified fast spin echo sequence according to the area compensation amount of the readout pre-phasing gradient and the gradient delay compensation amount of the readout gradient of each gradient axis to obtain a corrected fast spin echo sequence;

[0036] The magnetic resonance sequence correction module is further used to use the corrected fast spin echo sequence as a new designated fast spin echo sequence, so as to re-use the designated fast spin echo sequence to pre-scan the object to be measured, until the area compensation amount of the readout pre-dephasing gradient and the gradient delay compensation amount of the readout gradient of each gradient axis are both lower than a preset threshold value, and the obtained corrected fast spin echo sequence is used as the final fast spin echo sequence;

[0037] The magnetic resonance imaging module is communicatively connected with the magnetic resonance sequence correction module, and is used for scanning the object to be measured by using the final fast spin echo sequence to obtain a magnetic resonance image of the object to be measured; wherein, when the object to be measured is scanned by using the final fast spin echo sequence, the layer coding gradient and the layer coding gradient rewinding gradient are turned on.

[0038] In a third aspect, the present invention provides an electronic device, comprising:

[0039] a memory for storing computer program instructions; and,

[0040] A processor is used to execute the computer program instructions to complete the operation of the ultra-low field magnetic resonance imaging method as described in any one of the above.

[0041] In a fourth aspect, the present invention provides a computer program product, comprising a computer program or instructions, wherein the computer program or instructions, when executed by a computer, implements the ultra-low field magnetic resonance imaging method as described in any one of the above.

[0042] The beneficial effects of the present invention are:

[0043] The present invention discloses an ultra-low field magnetic resonance imaging method, system, electronic device and product, which can improve the imaging quality and shorten the time of magnetic resonance scanning. Specifically, in the implementation process of the present invention, the gradient performance difference of different spokes on each gradient axis is understood through pre-scanning, and based on the pre-scanning result, the area of ​​the pre-dephasing gradient Grp and the gradient delay of the readout gradient Gr are compensated for for each gradient axis of different spokes in an iterative manner, so that the delay difference of the gradient of the two gradient axes read out by the radial acquisition method is as small as possible, and the center of the k space is aligned as much as possible to reduce the offset, so as to reduce the influence caused by the gradient performance difference, thereby improving the image quality; at the same time, the present invention improves the imaging sequence, and by correcting the fast spin echo sequence, a better imaging effect can be obtained in the ultra-low field, so that the average number can be set to 1 at least, so that denser spokes can be collected, and two cycles are not required while improving the resolution, thereby shortening the scanning time under the premise of ensuring that the image resolution and quality meet the requirements.

[0044] Other beneficial effects of the present invention will be further described in the specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is a flow chart of an ultra-low field magnetic resonance imaging method in an embodiment;

[0046] Figure 2 It is a module block diagram of an ultra-low field magnetic resonance imaging system in an embodiment. DETAILED DESCRIPTION

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be briefly introduced below in combination with the drawings and the description of the embodiments or the prior art. Obviously, the following description of the structure of the drawings is only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention.

[0048] Embodiment 1:

[0049] This embodiment discloses an ultra-low field magnetic resonance imaging method, which can be executed by, but is not limited to, a computer device or a virtual machine with certain computing resources, such as a personal computer, a smart phone, a personal digital assistant, or a wearable device, or by a virtual machine.

[0050] like Figure 1 As shown, an ultra-low field magnetic resonance imaging method may include but is not limited to the following steps:

[0051] S1. Pre-scan the object to be measured using a specified fast spin echo sequence; wherein, when pre-scanning the object to be measured, the layer coding gradient Gse and the layer coding gradient rewinding gradient Gsr are not turned on, that is, there is no inter-layer coding gradient during the pre-scanning of the object to be measured, thereby ensuring that the scan only focuses on the optimization of the readout direction without being affected by the layer coding.

[0052] In this embodiment, when the layer selection direction (referring to the direction of selecting the imaging layer by applying the gradient field, which is used to determine the position and thickness of the imaging layer, and different types of layer selection can be achieved according to different gradient field directions) is the Z axis, and the readout direction (that is, the direction of the phase encoding gradient, which can achieve the control of the spatial resolution and quality of the image) is the X axis and the Y axis, the readout pre-dephasing gradient Grp and the readout gradient Gr are allocated to the X axis and the Y axis as follows:

[0053] , ;

[0054] , ;

[0055] In the formula, Rotate the spokes to a specified angle; To read out the distribution of the pre-dispersion gradient Grp to the X-axis; To read out the distribution of the pre-dispersion gradient Grp to the Y axis; To read out the distribution of the gradient Gr to the X-axis; To read the distribution amount of the gradient Gr to the Y axis.

[0056] In step S1, the designated fast spin echo sequence adopts a 3D-FSE (3D-Fast Spin Echo) sequence, and the ETL (Echo Train Length) direction of the designated fast spin echo sequence is the layer coding direction, that is, the direction of the echo train is consistent with the layer coding direction, so as to improve the imaging efficiency and quality. It should be noted that, in this embodiment, the designated fast spin echo sequence adopts a 3D-FSE sequence, which can facilitate the acquisition of high-quality images in a shorter time.

[0057] This embodiment improves the imaging sequence, and by improving the phase cycle mode of the fast spin echo sequence, a better imaging effect can be obtained in the ultra-low field, so that the minimum number of averages can be set to 1, so that denser spokes can be collected, and the resolution is improved without requiring two cycles, thereby shortening the scanning time under the premise of ensuring that the image resolution and quality meet the requirements. Specifically, in step S1, when the specified fast spin echo sequence is used to pre-scan the object to be measured, two different phase cycle sequences are applied to two adjacent spokes.

[0058] The phase cycle sequence of the traditional CPMG sequence can be [+x, +y, +y, +y, …] and [+x, -y, -y, -y, …]. The two phase cycle sequences can eliminate the free induction decay (FID) signal and ringing signal in the echo pulse, thereby reducing image artifacts. However, this phase cycle method requires at least two averages (i.e., two phase cycles), and the acquisition time is relatively long.

[0059] In this embodiment, by optimizing the setting of the phase cycle in the specified fast spin echo sequence, two different phase cycle sequences (such as [+x, +y, +y, +y, ...] and [+x, -y, -y, -y, ...]) are respectively applied to two adjacent spokes, so that the embodiment can eliminate the artifacts with only one averaging, that is, the phase cycle technology can be used to eliminate the free induction decay signal and the ringing signal of the refocusing pulse, and the effect of artifact elimination can still be guaranteed, and the acquisition time can be reduced, so that the acquisition time is shortened by half. As long as the two adjacent spokes have different phase cycle sequences, the artifact elimination can be achieved without repeated acquisition.

[0060] S2. Acquire multiple echo signals of each gradient axis generated by the object to be measured, and obtain multiple echo spoke images corresponding to the multiple echo signals one by one based on the multiple echo signals of each gradient axis; it should be understood that the multiple echo signals can be called an echo chain, each echo signal corresponds to the k-space data of a time point, and the multiple echo signals will fill the data in the k-space.

[0061] In step S2, a radial acquisition method is used to acquire multiple echo signals generated by the object to be measured, and the amplitude of the readout pre-dephasing gradient Grp is kept consistent with the amplitude of the readout gradient Gr to ensure the consistency of phase encoding and reduce artifacts.

[0062] It should be noted that in step S1, when the object to be measured is pre-scanned using a specified fast spin echo sequence, scanning is performed in multiple specific gradient directions, such as four gradient directions including +X direction (along the positive direction of the X axis), X direction (along the negative direction of the X axis), +Y direction (along the positive direction of the Y axis) and Y direction (along the negative direction of the Y axis). At this time, each gradient direction will generate a set of echo data; taking the +X direction as an example, a set of echo data generated in the +X direction is subjected to inverse Fourier transform, and a set of echo spoke images corresponding to the direction can be obtained. Correspondingly, in step S2, any echo signal generated by the object to be measured includes echo data in multiple gradient directions, and the echo image corresponding to any echo signal includes echo spoke images in multiple gradient directions.

[0063] It should be noted that by performing Fourier transform processing on the multiple echo signals respectively, a plurality of echo spoke images corresponding to the multiple echo signals can be obtained, wherein each echo spoke image represents a magnetic resonance image of a specific gradient direction at a specific time point, and these data jointly participate in the reconstruction of the echo image.

[0064] S3. Acquire the first echo spoke image and the second echo spoke image of each gradient axis from the multiple echo spoke images of each gradient axis respectively, and obtain the area compensation amount of the readout pre-phase gradient Grp and the gradient delay compensation amount of the readout gradient Gr of each gradient axis according to the first echo spoke image and the second echo spoke image of each gradient axis; it should be noted that the first echo spoke image and the second echo spoke image are echo spoke images generated based on the first echo signal and the second echo signal of the multiple echo signals respectively, wherein the first echo signal is collected at the initial time point, and it usually has the highest signal-to-noise ratio and the lowest attenuation effect, and the second echo signal is collected in a short time after the first echo, and it usually also has a higher image quality, and the linear phase difference and image quality of the first echo spoke image and the second echo spoke image are usually good, and the linear phase difference between the two reflects the phase change caused by the uneven magnetic field in the readout direction, the inaccurate encoding area of ​​the readout pre-phase gradient and other system errors.

[0065] In this embodiment, the area compensation amount of the readout pre-dephasing gradient Grp of each gradient axis can be used to compensate for the signal phase error caused by the readout gradient Gr of each gradient axis, thereby improving the quality of the final image. Gradient delay refers to the time difference of the signal arriving at the detector at different time points. By calculating these delays, the time error caused by each gradient axis can be compensated and imaging artifacts can be reduced.

[0066] Specifically, in step S3, the area compensation amount of the readout pre-phase gradient Grp of any gradient axis includes a positive area compensation amount and a negative area compensation amount, and the gradient delay compensation amount of the readout gradient Gr of any gradient axis includes a positive gradient delay compensation amount and a negative gradient delay compensation amount; when any gradient axis is the X axis, its positive area compensation amount is:

[0067] ;

[0068] In the formula, is the image resolution of +X axis; N is the total number of readout points in +X direction; is the phase operation function; Read point for +X direction n The corresponding first echo spoke image, n=1,2,3,…,N-1 ; Read point for +X direction n the corresponding second echo spoke image;

[0069] When any of the gradient axes is the X axis, the positive gradient delay compensation amount is:

[0070] ;

[0071] In the formula, is the readout point sampling interval in the +X direction.

[0072] It should be noted that based on the above steps, the area compensation amount of the readout pre-phase gradient Grp in the +X direction, -X direction, +Y direction and -Y direction can be calculated: And the gradient delay compensation of its readout gradient Gr .

[0073] S4. According to the area compensation amount of the readout pre-dephasing gradient Grp and the gradient delay compensation amount of the readout gradient Gr of each gradient axis, the specified fast spin echo sequence is corrected to obtain a corrected fast spin echo sequence.

[0074] In step S4, the specified fast spin echo sequence is corrected according to the area compensation amount of the readout pre-dephasing gradient Grp and the gradient delay compensation amount of the readout gradient Gr of each gradient axis to obtain a corrected fast spin echo sequence, including:

[0075] S401. Acquire the spoke rotation angle in the specified fast spin echo sequence;

[0076] S402. Obtain the corrected readout pre-phasing gradient and the corrected gradient delay compensation of each gradient axis according to the spoke rotation angle in the specified fast spin echo sequence, the area compensation of the readout pre-phasing gradient Grp of each gradient axis, and the gradient delay compensation of the readout gradient Gr;

[0077] Specifically, the gradient axis includes an X-axis and a Y-axis. Correspondingly, the corrected readout pre-phase gradient area of ​​the X-axis is:

[0078] ;

[0079] The corrected readout pre-phase gradient of the Y axis is:

[0080] ;

[0081] The corrected gradient delay compensation of the X-axis is:

[0082] ;

[0083] The corrected gradient delay compensation of the Y axis is:

[0084] ;

[0085] In the formula, To specify the spoke rotation angle; is the ideal readout pre-phase gradient area; It is a sign function that takes the value 1 when the independent variable is positive and -1 when it is negative.

[0086] S403. Correct the designated fast spin echo sequence according to the corrected readout pre-phasing gradients and the corrected gradient delay compensation amounts of each gradient axis to obtain a corrected fast spin echo sequence.

[0087] In step S403 of this embodiment, the designated fast spin echo sequence is corrected according to the corrected readout pre-phasing gradients and the corrected gradient delay compensation amounts of each gradient axis to obtain a corrected fast spin echo sequence, including:

[0088] Performing an initial correction on the designated fast spin echo sequence according to the corrected readout pre-phasing gradient and the corrected gradient delay compensation amount of each gradient axis to obtain an initial corrected fast spin echo sequence;

[0089] The initial corrected fast spin echo sequence is corrected twice to obtain a corrected fast spin echo sequence.

[0090] Specifically, in this embodiment, when the initial corrected fast spin echo sequence is corrected for the second time, the uncoded state is first maintained, and the initial corrected fast spin echo sequence is used to pre-scan the object to be measured to obtain data at all spoke angles, and then the area compensation amount of the readout pre-phasing gradient Grp of each gradient axis and the gradient delay compensation amount of the readout gradient Gr are calculated again, and the calculated area compensation amount of the readout pre-phasing gradient Grp of each gradient axis is directly allocated to the X-axis and the Y-axis according to the cosine and sine relationship, and the polarity is no longer distinguished, and the calculated gradient delay compensation amount of the readout gradient Gr is directly and equally assigned to the X-axis and the Y-axis without considering the polarity, thereby obtaining a corrected fast spin echo sequence.

[0091] S5. The modified fast spin echo sequence is used as a new designated fast spin echo sequence, so as to re-adopt the designated fast spin echo sequence to pre-scan the object to be measured, until the area compensation amount of the readout pre-dephasing gradient Grp and the gradient delay compensation amount of the readout gradient Gr of each gradient axis are both lower than a preset threshold value, and the obtained modified fast spin echo sequence is used as the final fast spin echo sequence.

[0092] S6. Scanning the object to be measured using the final fast spin echo sequence to obtain a magnetic resonance image of the object to be measured; wherein, when scanning the object to be measured using the final fast spin echo sequence, the layer encoding gradient Gse and the layer encoding gradient rewind gradient Gsr are turned on.

[0093] This embodiment can improve the imaging quality and shorten the time of magnetic resonance scanning. Specifically, in the implementation process of this embodiment, the gradient performance difference of different spokes on each gradient axis is understood through pre-scanning, and based on the pre-scanning results, the area of ​​the pre-dephasing gradient Grp and the gradient delay of the readout gradient Gr are compensated for in an iterative manner for each gradient axis of different spokes, so that the delay difference of the gradients of the two gradient axes read out by the radial acquisition method is as small as possible, and the center of the k-space is aligned as much as possible to reduce the offset, so as to reduce the impact caused by the gradient performance difference, thereby improving the image quality; at the same time, this embodiment improves the imaging sequence, and by improving the phase cycle mode of the fast spin echo sequence, a better imaging effect can be obtained at an ultra-low field, so that the minimum average number can be set to 1, so that denser spokes can be collected, and two cycles are not required while improving the resolution, thereby shortening the scanning time under the premise of ensuring that the image resolution and quality meet the requirements.

[0094] Embodiment 2:

[0095] This embodiment discloses an ultra-low field magnetic resonance imaging system for implementing the ultra-low field magnetic resonance imaging method in embodiment 1; Figure 2 As shown, the ultra-low field magnetic resonance imaging system comprises:

[0096] A magnetic resonance sequence correction module, used for pre-scanning the object to be measured by using a specified fast spin echo sequence; wherein, when the object to be measured is pre-scanned, the layer coding gradient and the layer coding gradient rewinding gradient are not turned on;

[0097] The magnetic resonance sequence correction module is further used to obtain a plurality of echo signals of each gradient axis generated by the object to be measured, and obtain a plurality of echo spoke images corresponding to the plurality of echo signals one by one according to the plurality of echo signals of each gradient axis;

[0098] The magnetic resonance sequence correction module is further used to respectively obtain a first echo spoke image and a second echo spoke image of each gradient axis from a plurality of echo spoke images of each gradient axis, and obtain an area compensation amount of a readout pre-phasing gradient and a gradient delay compensation amount of a readout gradient of each gradient axis according to the first echo spoke image and the second echo spoke image of each gradient axis;

[0099] The magnetic resonance sequence correction module is further used to correct the specified fast spin echo sequence according to the area compensation amount of the readout pre-phasing gradient and the gradient delay compensation amount of the readout gradient of each gradient axis to obtain a corrected fast spin echo sequence;

[0100] The magnetic resonance sequence correction module is further used to use the corrected fast spin echo sequence as a new designated fast spin echo sequence, so as to re-use the designated fast spin echo sequence to pre-scan the object to be measured, until the area compensation amount of the readout pre-dephasing gradient and the gradient delay compensation amount of the readout gradient of each gradient axis are both lower than a preset threshold value, and the obtained corrected fast spin echo sequence is used as the final fast spin echo sequence;

[0101] The magnetic resonance imaging module is communicatively connected with the magnetic resonance sequence correction module, and is used for scanning the object to be measured by using the final fast spin echo sequence to obtain a magnetic resonance image of the object to be measured; wherein, when the object to be measured is scanned by using the final fast spin echo sequence, the layer coding gradient and the layer coding gradient rewinding gradient are turned on.

[0102] It should be noted that the working process, working details and technical effects of the ultra-low field magnetic resonance imaging system provided in this embodiment 2 can be found in embodiment 1 and will not be described in detail here.

[0103] Embodiment 3:

[0104] Based on Embodiment 1 or 2, this embodiment discloses an electronic device, which may be a smart phone, a tablet computer, a laptop computer, or a desktop computer, etc. The electronic device may be called a user terminal, a portable terminal, a desktop terminal, etc. The electronic device includes:

[0105] a memory for storing computer program instructions; and,

[0106] A processor is used to execute the computer program instructions to complete the operation of the ultra-low field magnetic resonance imaging method as described in any one of Example 1.

[0107] Embodiment 4:

[0108] Based on any one of embodiments 1 to 3, this embodiment discloses a computer program product, including a computer program or instructions, which, when executed by a computer, implements the ultra-low field magnetic resonance imaging method as described in any one of embodiment 1.

[0109] Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, and optionally, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An ultra-low field magnetic resonance imaging method, characterized in that: include: A specified fast spin echo sequence is used to pre-scan the object to be measured; wherein, when the object to be measured is pre-scanned, the layer coding gradient and the layer coding gradient rewind gradient are not turned on; Acquire a plurality of echo signals of each gradient axis generated by the object to be measured, and obtain a plurality of echo spoke images corresponding to the plurality of echo signals one by one according to the plurality of echo signals of each gradient axis; Acquire a first echo spoke image and a second echo spoke image of each gradient axis from a plurality of echo spoke images of each gradient axis, and obtain an area compensation amount of a readout pre-phasing gradient and a gradient delay compensation amount of a readout gradient of each gradient axis according to the first echo spoke image and the second echo spoke image of each gradient axis; Correcting the designated fast spin echo sequence according to the area compensation amount of the readout pre-phasing gradient and the gradient delay compensation amount of the readout gradient of each gradient axis to obtain a corrected fast spin echo sequence; The modified fast spin echo sequence is used as a new designated fast spin echo sequence, so as to re-use the designated fast spin echo sequence to pre-scan the object to be measured, until the area compensation amount of the readout pre-dephasing gradient and the gradient delay compensation amount of the readout gradient of each gradient axis are both lower than a preset threshold value, and the obtained modified fast spin echo sequence is used as a final fast spin echo sequence; The object to be measured is scanned by using the final fast spin echo sequence to obtain a magnetic resonance image of the object to be measured; wherein, when the object to be measured is scanned by using the final fast spin echo sequence, a layer coding gradient and a layer coding gradient rewind gradient are turned on; The area compensation amount of the readout pre-phase gradient of any gradient axis includes a positive area compensation amount and a negative area compensation amount, and the gradient delay compensation amount of the readout gradient of any gradient axis includes a positive gradient delay compensation amount and a negative gradient delay compensation amount; when any gradient axis is the X axis, its positive area compensation amount is: ； In the formula, is the image resolution of +X axis; N is the total number of readout points in +X direction; is the phase operation function; Read point for +X direction n The corresponding first echo spoke image, n=1,2,3,…,N-1 ; Read point for +X direction n the corresponding second echo spoke image; When any of the gradient axes is the X axis, the positive gradient delay compensation amount is: ； In the formula, is the readout point sampling interval in the +X direction.

2. The ultra-low field magnetic resonance imaging method according to claim 1, characterized in that: The designated fast spin echo sequence adopts a 3D-FSE sequence, and the ETL direction of the designated fast spin echo sequence is a layer encoding direction.

3. The ultra-low field magnetic resonance imaging method according to claim 1, characterized in that: When the object to be measured is pre-scanned using a designated fast spin echo sequence, two different phase cycle sequences are applied to two adjacent spokes.

4. The ultra-low field magnetic resonance imaging method according to claim 1, characterized in that: A radial acquisition method is used to acquire multiple echo signals generated by the object to be measured, and the amplitude of the readout pre-phasing gradient is consistent with the amplitude of the readout gradient.

5. The ultra-low field magnetic resonance imaging method according to claim 1, characterized in that: The specified fast spin echo sequence is corrected according to the area compensation amount of the readout pre-phasing gradient and the gradient delay compensation amount of the readout gradient of each gradient axis to obtain a corrected fast spin echo sequence, including: Acquiring a spoke rotation angle in the specified fast spin echo sequence; Obtaining a corrected readout prephasing gradient and a corrected gradient delay compensation amount for each gradient axis according to the spoke rotation angle in the specified fast spin echo sequence, an area compensation amount of a readout prephasing gradient for each gradient axis, and a gradient delay compensation amount of a readout gradient; The designated fast spin echo sequence is corrected according to the corrected readout pre-phasing gradient and the corrected gradient delay compensation amount of each gradient axis to obtain a corrected fast spin echo sequence.

6. The ultra-low field magnetic resonance imaging method according to claim 5, characterized in that: The specified fast spin echo sequence is corrected according to the corrected readout pre-phasing gradient and the corrected gradient delay compensation amount of each gradient axis to obtain a corrected fast spin echo sequence, including: Performing an initial correction on the designated fast spin echo sequence according to the corrected readout pre-phasing gradient and the corrected gradient delay compensation amount of each gradient axis to obtain an initial corrected fast spin echo sequence; The initial corrected fast spin echo sequence is corrected twice to obtain a corrected fast spin echo sequence.

7. An ultra-low field magnetic resonance imaging system, characterized in that: Used to implement the ultra-low field magnetic resonance imaging method as claimed in any one of claims 1 to 6; The ultra-low field magnetic resonance imaging system comprises: A magnetic resonance sequence correction module, used for pre-scanning the object to be measured by using a specified fast spin echo sequence; wherein, when the object to be measured is pre-scanned, the layer coding gradient and the layer coding gradient rewinding gradient are not turned on; The magnetic resonance sequence correction module is further used to obtain a plurality of echo signals of each gradient axis generated by the object to be measured, and obtain a plurality of echo spoke images corresponding to the plurality of echo signals one by one according to the plurality of echo signals of each gradient axis; The magnetic resonance sequence correction module is further used to respectively obtain a first echo spoke image and a second echo spoke image of each gradient axis from a plurality of echo spoke images of each gradient axis, and obtain an area compensation amount of a readout pre-phasing gradient and a gradient delay compensation amount of a readout gradient of each gradient axis according to the first echo spoke image and the second echo spoke image of each gradient axis; The magnetic resonance sequence correction module is further used to correct the specified fast spin echo sequence according to the area compensation amount of the readout pre-phasing gradient and the gradient delay compensation amount of the readout gradient of each gradient axis to obtain a corrected fast spin echo sequence; The magnetic resonance sequence correction module is further used to use the corrected fast spin echo sequence as a new designated fast spin echo sequence, so as to re-use the designated fast spin echo sequence to pre-scan the object to be measured, until the area compensation amount of the readout pre-dephasing gradient and the gradient delay compensation amount of the readout gradient of each gradient axis are both lower than a preset threshold value, and the obtained corrected fast spin echo sequence is used as the final fast spin echo sequence; The magnetic resonance imaging module is communicatively connected with the magnetic resonance sequence correction module, and is used for scanning the object to be measured by using the final fast spin echo sequence to obtain a magnetic resonance image of the object to be measured; wherein, when the object to be measured is scanned by using the final fast spin echo sequence, the layer coding gradient and the layer coding gradient rewinding gradient are turned on.

8. An electronic device, characterized in that: include: a memory for storing computer program instructions; as well as, A processor, configured to execute the computer program instructions to complete the operation of the ultra-low field magnetic resonance imaging method as claimed in any one of claims 1 to 6.

9. A computer program product comprising a computer program or instructions, characterized in that The computer program or the instructions implement the ultra-low field magnetic resonance imaging method according to any one of claims 1 to 6 when executed by a computer.

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