Magnetic resonance image processing method and device, and computer-readable storage medium

Abstract

Embodiments of the present invention provide a magnetic resonance image processing method and apparatus, and a computer-readable storage medium. The method includes: determining a center angle; converting a radio frequency field map of a radio frequency transmitting coil into an angle map based on the center angle; obtaining a radio frequency transmission field map of the radio frequency transmitting coil based on trigonometric function values ​​of the angle map; and correcting a magnetic resonance image to be corrected based on the radio frequency transmission field map.

Description

Technical Field

[0001] The present invention relates to the field of medical imaging, and in particular to a magnetic resonance image processing method and device. Background Art

[0002] In current magnetic resonance imaging technology, before performing an imaging scan on a patient, a calibration scan (pre-scan) can be performed to obtain the surface coil's RF receive field map. This surface coil's receive RF field map can then be used to enhance image uniformity, enabling a more uniform image to be obtained after the imaging scan. Generally, the RF field map of a transmitting coil (e.g., a body coil) is assumed to be uniformly distributed. Therefore, during the pre-scan, a body coil image and a surface coil image can be obtained separately. Based on the body coil image, the surface coil image, and the body coil's RF field map, the surface coil's RF receive field map can be derived.

[0003] With the rapid development of magnetic resonance imaging (MRI) technology, the body coils used in MRI systems may experience uneven sensitivity due to variations in size or other parameters, which can also lead to uneven images. To further enhance image uniformity, those skilled in the art have proposed using the body coil's radiofrequency field pattern to correct the image.

[0004] Although such correction can improve the uniformity of the image, there are still some shadows in the image and the uniformity still needs to be improved.

[0005] Therefore, it is necessary to provide a new magnetic resonance image processing method and apparatus that can obtain magnetic resonance images with enhanced uniformity. Summary of the Invention

[0006] In one aspect, the present invention provides a method for processing magnetic resonance images, comprising:

[0007] Determine the center angle;

[0008] converting a radio frequency field pattern of the radio frequency transmitting coil into an angle pattern based on the central angle;

[0009] Acquire a radio frequency transmission field diagram of the radio frequency transmitting coil based on the trigonometric function value of the angle diagram; and

[0010] The magnetic resonance image to be corrected is corrected based on the radio frequency transmit field map.

[0011] On the other hand, the step of obtaining the RF transmission field map of the RF transmitting coil further includes: determining a weight parameter, and adjusting the trigonometric function value of the angle map based on the weight parameter, wherein the RF transmission field map is obtained based on the adjusted trigonometric function value.

[0012] On the other hand, based on the formula Obtain the radio frequency transmission field map, wherein: is the radio frequency transmission field diagram, C n is the weight parameter, C n is greater than 0, n is greater than 0, θ is the angle value in the angle diagram, and f(θ) is a trigonometric function with θ as the independent variable.

[0013] In another aspect, the trigonometric function values ​​of the angle graph include sine function values ​​of the angle graph.

[0014] In another aspect, the center angle is determined based on a flip angle of a radio frequency transmit pulse of a scanning sequence for generating the magnetic resonance image.

[0015] In another aspect, the method further comprises: dividing the corrected magnetic resonance image by the radio frequency field map of the radio frequency transmitting coil to obtain a further corrected image.

[0016] On the other hand, the magnetic resonance image to be corrected is an image obtained after image correction based on the radio frequency field map of the radio frequency transmitting coil.

[0017] On the other hand, the center angle is 90 degrees.

[0018] Another aspect of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium includes a stored computer program, wherein when the computer program is executed, the method according to any one of claims 1 to 8 is executed.

[0019] Another aspect of the present invention provides a magnetic resonance image processing device, comprising:

[0020] An angle determination module, which is used to determine the center angle;

[0021] a conversion module, configured to convert a radio frequency field pattern of the radio frequency transmitting coil into an angle pattern based on the center angle;

[0022] a radio frequency transmission field pattern acquisition module, configured to acquire a radio frequency transmission field pattern of the radio frequency transmission coil based on a trigonometric function value of the angle pattern; and

[0023] A correction module is used to correct the magnetic resonance image to be corrected based on the radio frequency transmission field map.

[0024] On the other hand, the RF transmission field map acquisition module is used to:

[0025] determining a weight parameter, and adjusting the trigonometric function value of the angle map based on the weight parameter; and,

[0026] The radio frequency transmission field map is obtained based on the adjusted trigonometric function value.

[0027] On the other hand, the RF transmission field map acquisition module is used to obtain the RF transmission field map based on the formula Obtain the radio frequency transmission field map, wherein: is the radio frequency transmission field diagram, C n is the weight parameter, C n is greater than 0, n is greater than 0, θ is the angle value in the angle diagram, and f(θ) is a trigonometric function with θ as the independent variable.

[0028] Other features and aspects will become apparent from the following detailed description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention may be better understood by describing exemplary embodiments of the present invention in conjunction with the accompanying drawings, in which:

[0030] Figure 1 is a schematic structural diagram of an embodiment of a magnetic resonance imaging system;

[0031] Figure 2 A flowchart of a magnetic resonance image processing method provided by one embodiment of the present invention;

[0032] Figure 3 A block diagram of a magnetic resonance image processing apparatus according to an embodiment of the present invention;

[0033] Figure 4 The result of processing the magnetic resonance image to be corrected by the existing technology;

[0034] Figure 5 This is a result of processing the magnetic resonance image to be corrected by an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The specific embodiments of the present invention will be described below. It should be noted that in the specific description of these embodiments, in order to provide a concise description, this specification cannot provide a detailed description of all the features of the actual embodiments. It should be understood that in the actual implementation of any embodiment, just as in the process of any engineering project or design project, in order to achieve the specific goals of the developer and to meet system-related or business-related restrictions, various specific decisions are often made, and this will also change from one embodiment to another. In addition, it can also be understood that although the efforts made in this development process may be complex and lengthy, for ordinary technicians in the field related to the content disclosed by the present invention, some design, manufacturing or production changes based on the technical content disclosed in this disclosure are just conventional technical means and should not be understood as the content of this disclosure being insufficient.

[0036] Unless otherwise defined, the technical or scientific terms used in the claims and description shall have the usual meaning understood by persons of ordinary skill in the technical field to which the invention belongs. The words "first", "second" and similar terms used in the description and claims of the patent application of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "one" or "a" do not indicate a quantity limitation, but rather indicate the existence of at least one. Words such as "include" or "comprising" mean that the elements or objects appearing before "include" or "comprising" cover the elements or objects listed after "include" or "comprising" and their equivalent elements, and do not exclude other elements or objects. Words such as "connected" or "connected" and similar terms are not limited to physical or mechanical connections, nor are they limited to direct or indirect connections.

[0037] The magnetic resonance image uniformity correction method in the embodiments of the present invention can be used in a magnetic resonance imaging device to acquire a magnetic resonance image of a patient's part to be examined. Those skilled in the art will appreciate that the magnetic resonance imaging device may include a main magnet for generating a main magnetic field, a radio frequency system for generating a radio frequency field, and a gradient system for generating a gradient field. The radio frequency system may include a body coil and a receiving coil. The body coil may serve as a radio frequency transmitting coil and / or a radio frequency receiving coil, and the surface coil may serve as a radio frequency receiving coil. The magnetic resonance imaging device may also include a computer system that can control a pulse generator to generate radio frequency pulses, gradient pulses, etc., to control the radio frequency system and gradient system to emit signals acting on the human body, ultimately receiving magnetic resonance signals from the human body for image reconstruction.

[0038] Figure 1 1 shows a schematic structural diagram of a magnetic resonance imaging (MRI) system, which includes a scanner 110. The scanner 110 is used to perform magnetic resonance scanning on an object (e.g., a human body) 16 to generate image data of a region of interest of the object 16, which may be a predetermined imaging site or imaging tissue.

[0039] The magnetic resonance imaging system 100 may include a controller 120 coupled to the scanner 110 for controlling the scanner 110 to perform the aforementioned magnetic resonance scanning process. Specifically, the controller 120 may send sequence control signals to relevant components of the scanner 110 (e.g., a radio frequency generator and a gradient coil driver, etc., described below) via a sequence generator (not shown), thereby causing the scanner 110 to perform a preset scanning sequence.

[0040] Those skilled in the art will understand that the above-mentioned "scan sequence" refers to a combination of pulses with specific amplitude, width, direction and timing applied when performing magnetic resonance imaging scans. These pulses can generally include, for example, radio frequency pulses and gradient pulses. The radio frequency pulses can include, for example, radio frequency transmission pulses and radio frequency refocusing pulses for exciting protons in the human body to resonate. The gradient pulses can include, for example, slice selection gradient pulses, phase encoding gradient pulses, frequency encoding gradient pulses, etc. Generally, multiple scan sequences can be pre-set in the magnetic resonance system to enable the selection of a sequence that is compatible with clinical detection requirements. The clinical detection requirements can include, for example, imaging site, imaging function, imaging effect, etc.

[0041] In practice, different scanning sequence types may need to be selected based on different clinical applications, such as echo planar imaging (EPI) sequence, gradient echo (GRE) sequence, spin echo (SE) sequence, fast spin echo (FSE) sequence, single-shot fast spin echo (SSFSE), diffusion-weighted imaging (DWI) sequence, inversion recovery (IR) sequence, etc., and each scanning sequence may have different scanning sequence parameters in different clinical applications, such as the number of excitations (Nex), echo time, echo chain length, repetition time, inversion recovery time, etc.

[0042] The number of excitations mentioned above refers to the number of times the same tissue is excited, for example, it may be the number of times the radio frequency emission pulses are applied.

[0043] In one example, the scanner 110 may include a main magnet assembly 111 , a couch 112 , a radio frequency generator 113 , a radio frequency transmit coil 114 , a surface coil 118 , a gradient coil driver 115 , a gradient coil assembly 116 , and a data acquisition unit 117 .

[0044] The main magnet assembly 111 generally includes an annular superconducting magnet defined in a housing, and the annular superconducting magnet is installed in an annular vacuum container. The annular superconducting magnet and its housing define a cylindrical space surrounding the object 16, such as Figure 1 The scanning cavity 119 is shown. The main magnet assembly 111 generates a constant magnetic field, namely the B0 field, along the Z direction of the scanning cavity 119. Generally, a relatively uniform portion of the B0 field is formed in the central region of the main magnet.

[0045] The bed 112 is used to carry the object 16 and respond to the control of the controller 120 to move along the Z direction to enter and exit the above-mentioned scanning cavity 119. For example, in one embodiment, the imaging volume of the object 16 can be positioned in the central area of ​​the scanning cavity where the magnetic field strength is relatively uniform, so as to facilitate scanning and imaging of the imaging volume of the object 16.

[0046] The Z direction is generally a direction extending from the head to the feet (or from the feet to the head) when the subject 16 is positioned on the bed 112 . For example, the selected layer may be a slice at any position in the Z direction.

[0047] The magnetic resonance imaging system 100 uses the formed B0 field to transmit a static magnetostatic pulse signal to the subject 16 located in the scanning cavity, so that the precession of protons in the resonance volume in the subject 16 is ordered, generating a longitudinal magnetization vector Mz.

[0048] The RF generator 113 is configured to generate RF pulses, such as RF excitation pulses, in response to control signals from the controller 120. These RF excitation pulses may have different flip angles depending on the scanning sequence. For example, in an FSE sequence, the flip angle of the RF excitation pulses is 90 degrees. These RF excitation pulses are amplified (e.g., by an RF power amplifier (not shown)) and then applied to the RF transmitting coil 114. This causes the RF transmitting coil 114 to transmit an RF field B1 orthogonal to the B0 field toward the subject 16, thereby exciting the nuclei within the resonance volume and generating a transverse magnetization vector Mxy.

[0049] The RF transmission coil 114 may include, for example, a body coil disposed along the periphery of the main magnet, or a head coil dedicated to head imaging.

[0050] After the RF excitation pulse ends, the proton group loses phase, the macroscopic transverse magnetization vector in the tissue gradually decays, and the transverse magnetization vector of the object 16 gradually returns to zero, generating a free induction decay signal, i.e., a magnetic resonance signal that can be acquired. This magnetic resonance signal can be acquired in the form of "echoes," such as spin echoes or gradient echoes. The echo acquisition method used may affect parameters such as scan time and imaging quality.

[0051] Spin echo typically uses radiofrequency refocusing pulses to realign the phases of proton groups, gradually increasing the transverse magnetization vector so that an echo can be acquired after the radiofrequency refocusing pulse ends. Scanning sequences employing spin echo include, but are not limited to, SE, FSE, and SSFSE. Within one repetition time, an SE sequence applies a single radiofrequency refocusing pulse after the radiofrequency transmit pulse and acquires a single echo. Each acquired echo is sequentially assigned to a phase encoding line in K-space. An FSE sequence applies multiple radiofrequency refocusing pulses after the radiofrequency transmit pulse within one repetition time and acquires multiple echoes. These echoes are assigned to multiple phase encoding lines in K-space.

[0052] The gradient coil driver 115 is configured to respond to a gradient pulse control signal or a shim control signal sent by the controller 120 to provide appropriate current / power to the gradient coil assembly 116 .

[0053] The gradient coil assembly 116 , on the one hand, forms a changing magnetic field in the imaging space to provide three-dimensional position information for the magnetic resonance signal, and on the other hand, is used to generate a compensation magnetic field for the B0 field to shim the B0 field.

[0054] The gradient coil assembly 116 may include three gradient coils, each configured to generate magnetic field gradients tilted along three mutually perpendicular spatial axes (e.g., the X-axis, the Y-axis, and the Z-axis). More specifically, the gradient coil assembly 116 applies a magnetic field gradient in a slice selection direction (Z-direction) to select a layer within the imaging volume. Those skilled in the art will appreciate that a layer is any one of a plurality of two-dimensional slices distributed along the Z-direction within the three-dimensional imaging volume. When scanning the image, the RF transmit coil 114 transmits RF excitation pulses to the layer within the imaging volume, thereby exciting the layer. The gradient coil assembly 116 applies a magnetic field gradient in a phase encoding direction (Y-direction) to phase encode the magnetic resonance signals of the excited layer. The gradient coil assembly 116 applies a gradient field in a frequency encoding direction to the subject 16 to frequency encode the magnetic resonance signals of the excited layer.

[0055] The body coil may be connected to a transmit / receive (T / R) switch (not shown), which may be controlled to switch the body coil between transmit and receive modes. In receive mode, the body coil may be used to receive magnetic resonance signals from the subject 16 .

[0056] The surface coil 118 is generally disposed close to a scanning site (region of interest) of the subject 16 (eg, covering or laying on the body surface of the subject 16 ), and is also used to receive magnetic resonance signals from the subject 16 .

[0057] The data acquisition unit 117 is used to respond to the data acquisition control signal of the controller 120 to acquire the above-mentioned magnetic resonance signals (for example, received by the body coil or the surface coil). In one embodiment, the data acquisition unit 117 may include, for example, a radio frequency preamplifier, a phase detector, and an analog / digital converter, wherein the radio frequency preamplifier is used to amplify the magnetic resonance signal, the phase detector is used to perform phase detection on the amplified magnetic resonance signal, and the analog / digital converter is used to convert the phase-detected magnetic resonance signal from an analog signal to a digital signal.

[0058] The data acquisition unit 117 is further configured to respond to data storage control signals from the controller 120 to store the digitized magnetic resonance signals (or echoes) in K-space. K-space is a space filled with raw magnetic resonance signal data containing spatially encoded information. Specifically, the data acquisition unit 117 responds to data storage control signals from the controller 120 to fill the digitized magnetic resonance signals into K-space in a specific manner.

[0059] The magnetic resonance imaging system 100 may include an image reconstruction unit 130 for performing an inverse Fourier transform on the data stored in the K-space to reconstruct a three-dimensional image or a series of two-dimensional slice images of the imaging volume of the subject 16. Specifically, the image reconstruction unit 130 may perform the above-mentioned image reconstruction based on communication with the controller 120.

[0060] The magnetic resonance imaging system 100 may include a processing unit 140 that can perform any necessary image post-processing on the aforementioned three-dimensional image or any image in the image sequence. This post-processing may include improvements or adaptive adjustments to the image in terms of contrast, uniformity, clarity, brightness, etc. Specifically, the processing unit 140 may communicate with the controller 120 to execute the image processing method of the present invention.

[0061] In one embodiment, the controller 120, the image reconstruction unit 130, and the processing unit 140 may each or jointly include a computer and a storage medium, on which a program for predetermined data processing to be executed by the computer is recorded. For example, the storage medium may store a program for performing imaging scanning, image reconstruction, image processing, etc. For example, it may store a program for performing the magnetic resonance image processing method according to an embodiment of the present invention. The storage medium may include, for example, a ROM, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, or a non-volatile memory card.

[0062] The magnetic resonance imaging system 100 may include a display unit 150 , which may be used to display an operation interface and various data, images or parameters generated during data acquisition and processing.

[0063] The magnetic resonance imaging system 100 includes a console 160, which may include user input devices such as a keyboard and a mouse. The controller 120 can respond to control commands generated by the user based on the operation console 160 or the operation panel / buttons provided on the main magnet housing to communicate with the scanner 110, the image reconstruction unit, the image processing unit 140, the display unit 150, etc.

[0064] Based on the above description, the controller unit 120 is used to control the various components / modules / units of the scanner 110, as well as the image reconstruction unit 130, image processing unit 140, etc., to perform corresponding operations in the pre-scan process, the main scan process, and image post-processing of magnetic resonance imaging. In one embodiment of the pre-scan process, magnetic resonance signals can be received by a body coil and a surface coil to reconstruct body coil images and surface coil images, respectively. The parameters for the main scan are set based on these body coil images and / or surface coil images. During the main scan process, a magnetic resonance image of the scanned area of ​​the subject 16 is acquired based on the set scan parameters. During post-processing, the (to-be-corrected) magnetic resonance image is further processed based on clinical diagnostic requirements.

[0065] The present invention has found that the uniformity of the magnetic resonance image S to be corrected is affected by the transmit field pattern of the transmit coil, the receive field pattern of the transmit coil, and the receive field pattern of the surface coil. The uniformity correction can be performed based on the following formula (1):

[0066]

[0067] In formula (1), S1 is the corrected first image, S is the original image, for example, an image reconstructed based on the original image data, and S body is the body coil image, S surf is the surface coil image. I is the ideal image (or real image), is the RF receiving field diagram of the surface coil, is the radio frequency receiving field map of the body coil. PSD (Pulse Sequence Design) is the scanning sequence used to generate the original image S, which includes multiple scanning parameters. Changes in the multiple scanning parameters will change the uniformity of the radio frequency transmitting field of the body coil. is the RF transmission field diagram of the body coil. Since it may change with the change of the scanning sequence, the RF transmission field diagram of the body coil can be further described as It can be considered as It is a function of the variables, and the function will change with the change of psd.

[0068] From formula (1), we can see that after eliminating the influence of the surface coil's RF receiving field pattern, the image quality is also affected by the body coil's RF transmitting field pattern. And the RF receiving field diagram of the body coil impact.

[0069] To further improve image quality, such as enhancing image uniformity, the first image S1 can be further processed based on the radio frequency field map of the body coil. The radio frequency field map of the body coil can be obtained by offline simulation of the body coil and pre-stored in the magnetic resonance imaging system. Furthermore, the radio frequency receiving field map of the body coil is identical to the radio frequency field map of the body coil obtained offline. Therefore, the magnetic resonance image S can be processed based on the following formula (2) to further eliminate image quality issues caused by the non-uniform radio frequency receiving field of the body coil.

[0070]

[0071] In formula (2), S2 is the corrected second image, is the radio frequency receiving field map of the body coil, which is the same as the radio frequency field map of the body coil obtained above. Therefore, by dividing the image to be processed S or the first image S1 by the radio frequency field map of the body coil, image problems caused by the non-uniformity of the radio frequency receiving field of the transmitting coil can be eliminated or further eliminated.

[0072] Since the RF transmission field of the body coil is affected by the scanning sequence used, and its sensitivity is affected by the imaging tissue parameters (such as longitudinal relaxation time T1 and transverse relaxation time T2), if the image quality problems caused by the uneven RF transmission field of the body coil are to be eliminated, a large amount of parameter estimation and calculation is required, or a large amount of resources are required to redesign the RF pulses and gradient pulses of the scanning sequence, which increases the difficulty and complexity of image correction.

[0073] Figure 2 FIG. 1 is a flow chart showing a method for processing magnetic resonance images according to an embodiment of the present invention. Figure 1 As shown, the method includes steps S21, S23, S25 and S27.

[0074] In step S21 , a center angle is determined. The center angle may be determined based on a flip angle of a radio frequency transmit pulse in a scanning sequence. The scanning sequence is a scanning sequence selected when generating a magnetic resonance image to be processed.

[0075] In one embodiment, the center angle is equal to the flip angle of the radio frequency transmission pulse in the scanning sequence. For example, if the magnetic resonance image is obtained by performing an FSE sequence, and the flip angle is set to 90 degrees when the sequence is performed, the center angle is determined to be 90 degrees.

[0076] In step S23, the radio frequency field map of the transmitting coil (e.g., the body coil) is converted into an angle map θ based on the center angle. As described above, the radio frequency field map of the transmitting coil can be obtained by offline simulation of the transmitting coil and pre-stored in the magnetic resonance imaging system. The radio frequency field map generally represents the intensity distribution of the radio frequency field. For example, the value of a pixel at the center of the radio frequency field map may be 1, while the value at the edge may be less than 1.

[0077] The present invention has found that the influence of the RF transmission field of the transmitting coil on the image signal is generally in a trigonometric function relationship (regardless of the form of the scanning sequence or sequence parameters used). Therefore, after the RF field map of the transmitting coil is converted into an angle in step S23, the RF transmission field map of the transmitting coil can be obtained in step S25 based on the trigonometric function value of the angle map θ. The trigonometric function may be any form of trigonometric function, such as sine function, cosine function, tangent function, cotangent function, secant function, cosecant function, etc.

[0078] In step S27, based on the radio frequency transmission field map Correct the magnetic resonance image to be corrected. For example, the magnetic resonance image to be corrected (such as image S, S1, S2 or an image after other image processing) can be divided by the radio frequency transmission field map of the body coil. A corrected image, ie, the corrected third image S3, can be obtained.

[0079] For example, when the magnetic resonance image to be corrected is the second image S2, it is further divided by the radio frequency transmission field map of the body coil according to the following formula (3): The corrected third image S3 is obtained.

[0080]

[0081] Figure 3 FIG. 4 is a flow chart showing a magnetic resonance imaging method according to another embodiment of the present invention. Figure 3 As shown, the method further includes an adjustment step, in which a weight parameter is determined and the trigonometric function value of the angle diagram is adjusted based on the weight parameter. Therefore, in step S25, the radio frequency transmission field diagram is obtained based on the adjusted trigonometric function value.

[0082] The weight parameters mentioned above may be empirical values, which may be embedded in the magnetic resonance imaging system after being verified in various aspects, to be used as optional parameters for image processing.

[0083] More specifically, the RF transmission field map can be obtained based on formula (4):

[0084]

[0085] Therefore, the above formula (3) can be expressed as:

[0086]

[0087] In one embodiment, formula (4) can be expanded into the following form:

[0088]

[0089] In formulas (4)-(6), C n is the weight parameter, C n is greater than 0 and can be any value between 0 and 1, or a value greater than or equal to 1. n is the number of times the trigonometric function value is adjusted based on the weight parameter. n is greater than 0. n and m can be integers or decimals. For example, n can be 1, 2, or a number between 0 and 2. θ is the angle value in the angle graph. f(θ) is the trigonometric function value with θ as the independent variable. f(θ) can be a sine function.

[0090] n may also be an empirical value, which, after being verified in various aspects, may be embedded in the magnetic resonance imaging system to be used as an optional parameter for image processing.

[0091] Therefore, in step S25, it may include receiving the weight parameter C selected based on the user operation. n The value of the weight parameter C may also include receiving the value of the adjustment number n selected based on the user operation. n Or when the value of the adjustment number n is unique, it can also be directly called to adjust the trigonometric function value.

[0092] In other embodiments, C n and n can also be the default value 1, so there is no need to select parameters or adjust the above trigonometric function values.

[0093] In other embodiments, when the image to be corrected is S (original image) or S1 (image corrected based on the surface coil radio frequency field map), the following steps may be further included after step S27:

[0094] The corrected image obtained after step S27 is further divided by the RF field pattern of the RF transmitting coil To obtain a further corrected image, therefore, after eliminating the image problem caused by the RF transmission field of the RF transmitting coil by executing the above steps S21, S23, S25 and step S27, the image problem caused by the RF receiving field of the RF transmitting coil is further eliminated.

[0095] In other embodiments, the image to be corrected in step S27 may be an image that has already been corrected based on the RF field map of the RF transmitting coil. Therefore, image quality issues caused by the RF receiving field of the RF transmitting coil are first eliminated, and then step S27 is performed to eliminate image quality issues caused by the RF transmitting field of the RF transmitting coil.

[0096] In addition, the image correction based on the surface coil RF field can be performed before, after, or between the image correction based on the RF receiving field of the RF transmitting coil and the image correction based on the RF transmitting field of the RF transmitting coil.

[0097] Based on the above description, an embodiment of the present invention may further provide a computer-readable storage medium comprising a stored computer program, wherein when the computer program is executed, the magnetic resonance image processing method of any of the above embodiments is executed.

[0098] Another embodiment of the present invention may further provide a magnetic resonance image processing apparatus, which can be used to process images reconstructed or processed by a magnetic resonance imaging system. The apparatus may be part of an image processing unit of the magnetic resonance imaging system, or may be independent and capable of communicating with the magnetic resonance imaging system.

[0099] Figure 3 A block diagram of an embodiment of the magnetic resonance image processing apparatus is shown in FIG. Figure 3 As shown, the apparatus includes an angle determination module 31, a conversion module 33, a radio frequency transmission field map acquisition module 35, and a correction module 37. The angle determination module 31 is configured to determine a center angle. The conversion module 33 is configured to convert the radio frequency field map of the radio frequency transmission coil into an angle map based on the center angle. The radio frequency transmission field map acquisition module 35 is configured to acquire the radio frequency transmission field map of the radio frequency transmission coil based on trigonometric function values ​​of the angle map. The correction module 37 is configured to correct the magnetic resonance image based on the radio frequency transmission field map.

[0100] In one embodiment, the RF transmission field pattern acquisition module 35 is further configured to determine a weight parameter, adjust a trigonometric function value of the angle pattern based on the weight parameter, and acquire the RF transmission field pattern based on the adjusted trigonometric function value.

[0101] Specifically, the radio frequency transmission field pattern acquisition module 35 acquires the radio frequency transmission field pattern using formula (4).

[0102] The magnetic resonance image processing apparatus may be configured to implement the magnetic resonance image processing method of any of the above embodiments.

[0103] The magnetic resonance image processing method and apparatus of an embodiment of the present invention converts the RF field map of the RF transmit coil into an angle map, obtains the RF transmit field map of the RF transmit coil based on the trigonometric function values ​​of the angle map, and performs image correction on the magnetic resonance image based on the RF transmit field map. This effectively removes shadows and other image inhomogeneities caused by an uneven RF transmit field. Furthermore, the embodiment of the present invention avoids the difficulty in obtaining the RF transmit field map of the RF transmit coil caused by redesigning the scan sequence or estimating, calculating, or modeling complex parameters (such as imaging tissue parameters T1 and T2 and other parameters related to the scan sequence).

[0104] Figure 4 shows the result of processing the magnetic resonance image to be corrected based on the prior art, Figure 5 The results of processing the magnetic resonance image to be corrected by the embodiment of the present invention are shown. Figure 4 、 Figure 5 It can be seen that Figure 5 Image ratio in Figure 4 The image in is more uniform, Figure 4 Some shadows in Figure 5 Did not appear in .

[0105] Several exemplary embodiments have been described above. However, it should be understood that various modifications may be made. For example, suitable results may be achieved if the described techniques are performed in a different order and / or if components in the described systems, architectures, devices, or circuits are combined in different ways and / or replaced or supplemented with other components or their equivalents. Accordingly, other implementations are also within the scope of the claims.

Claims

1. A magnetic resonance image processing method, comprising: Determine the center angle; converting a radio frequency field pattern of the radio frequency transmitting coil into an angle pattern based on the central angle; Determining a weight parameter, wherein the weight parameter is used to adjust a trigonometric function value of the angle graph, wherein the trigonometric function value is one of a sine function, a cosine function, a tangent function, a cotangent function, a secant function, and a cosecant function; The radio frequency transmission field diagram of the radio frequency transmission coil is obtained based on the trigonometric function value adjusted by the weight parameter, which includes: based on the formula Obtain the radio frequency transmission field map, wherein: is the radio frequency transmission field diagram, C n is the weight parameter, C n is greater than 0, n is greater than 0, θ is the angle value in the angle diagram, and f(θ) is the trigonometric function value of the angle value θ; and The magnetic resonance image to be corrected is corrected based on the radio frequency transmit field map.

2. The method according to claim 1, wherein The center angle is determined based on a flip angle of a radio frequency transmit pulse of a scanning sequence for generating the magnetic resonance image.

3. The method according to claim 1, wherein Also includes: The corrected magnetic resonance image is divided by the radio frequency field map of the radio frequency transmit coil to obtain a further corrected image.

4. The method according to claim 1, wherein The magnetic resonance image to be corrected is an image obtained after image correction based on a radio frequency field map of a radio frequency transmitting coil.

5. The method according to claim 1, wherein The center angle is 90 degrees.

6. A computer-readable storage medium comprising a stored computer program, wherein: When the computer program is executed, the method according to any one of claims 1 to 5 is performed.

7. A magnetic resonance image processing apparatus, comprising: An angle determination module, which is used to determine the center angle; a conversion module, configured to convert a radio frequency field pattern of the radio frequency transmitting coil into an angle pattern based on the center angle; A radio frequency transmission field map acquisition module is used to determine a weight parameter, the weight parameter is used to adjust the trigonometric function value of the angle map, and the radio frequency transmission field map acquisition module is further used to obtain the radio frequency transmission field map of the radio frequency transmitting coil based on the trigonometric function value adjusted by the weight parameter, including: based on the formula Obtain the radio frequency transmission field map, wherein: is the radio frequency transmission field diagram, C n is the weight parameter, C n is greater than 0, n is greater than 0, θ is the angle value in the angle diagram, and f(θ) is the trigonometric function value of the angle value θ; and A correction module is used to correct the magnetic resonance image to be corrected based on the radio frequency transmission field map.

Images