Magnetic resonance imaging method, apparatus, imaging device, and storage medium

Abstract

The application discloses a magnetic resonance imaging method and device, an imaging equipment and a storage medium. The initial layer thickness of the field of view (FOV) region and the initial selected layer is determined; then, the initial selected layer gradient is obtained based on the initial layer thickness; the initial selected layer gradient, the additional selected layer gradient and the radio frequency pulse are applied to the imaging region to excite the target selected layer, the target selected layer is inclined relative to the initial selected layer, and the target selected layer after the inclination covers the field of view (FOV) region; the magnetic resonance data corresponding to the target selected layer is obtained; and the target magnetic resonance image is obtained based on the magnetic resonance data. The target selected layer is inclined to suppress the artifacts caused by the edge field distortion, and the target selected layer after the inclination covers the field of view (FOV) region to keep the FOV region unchanged, so that the quality and the signal-to-noise ratio of the magnetic resonance image are improved.

Description

Technical Field

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

[0002] Magnetic resonance imaging (MRI) has become an important technique in medical imaging. MRI produces various artifacts, including folding artifacts and image processing-related artifacts. These artifacts can be confused with lesions or reduce the quality of medical examinations. Therefore, suppressing artifacts in MRI is of great significance. However, current artifact suppression techniques often reduce the resolution of MRI images. Summary of the Invention

[0003] The embodiments described in this specification aim to at least partially address one of the technical problems in the related art. To this end, the embodiments of this specification propose a magnetic resonance imaging method, apparatus, imaging device, and storage medium.

[0004] This specification provides a magnetic resonance imaging method, the method comprising:

[0005] Determine the field of view (FOV) area and the initial layer thickness for initial layer selection;

[0006] Based on the initial layer thickness, obtain the initial layer selection gradient;

[0007] The initial layer selection gradient, the additional layer selection gradient, and the radio frequency pulse are applied to the imaging region to excite the target layer selection and acquire the magnetic resonance data corresponding to the target layer selection; wherein, the target layer selection is tilted relative to the initial layer selection, and the tilted target layer selection covers the field of view (FOV) region;

[0008] The target magnetic resonance image is obtained based on the magnetic resonance data.

[0009] In one implementation, the direction of the additional layer selection gradient is either the phase coding direction or the frequency coding direction; the method for determining the additional layer selection gradient includes:

[0010] Determine the tilt angle of the target selected layer;

[0011] The additional layer selection gradient is determined based on the tilt angle and the initial layer selection gradient.

[0012] In one implementation, applying the initial layer-selection gradient, the additional layer-selection gradient, and the radio frequency pulse to the imaging region to excite the target layer and acquire the magnetic resonance data corresponding to the target layer includes:

[0013] The initial layer selection gradient, the first layer selection gradient, and the radio frequency pulse are applied to the imaging region to excite the first target layer selection and acquire the first magnetic resonance data corresponding to the first target layer selection; and / or

[0014] An initial layer selection gradient, a second layer selection gradient, and a radio frequency pulse are applied to the imaging region to excite a second target layer selection and acquire the second magnetic resonance data corresponding to the second target layer selection; wherein, the tilt angle of the first target layer selection is opposite to that of the second target layer selection, and the magnetic resonance data corresponding to the target layer selection includes the first magnetic resonance data and / or the second magnetic resonance data.

[0015] In one implementation, the determination of the first layer selection gradient and the second layer selection gradient includes:

[0016] Determine a first tilt angle, and determine the first layer selection gradient based on the first tilt angle and the initial layer selection gradient;

[0017] Determine the second tilt angle, and determine the second layer selection gradient based on the second tilt angle and the initial layer selection gradient.

[0018] In one embodiment, the second tilt angle is equal in magnitude to the first tilt angle but opposite in direction;

[0019] When the first layer selection gradient or the second layer selection gradient is applied, the field of view (FOV) size remains unchanged, and the target layer thickness of the target layer is determined based on the initial layer thickness, the first tilt angle, and the FOV size in the preset direction.

[0020] The interlayer spacing between adjacent scanning layers is determined by the field of view (FOV) size and the first tilt angle.

[0021] In one embodiment, the two ends of the field of view (FOV) region have a first oversampling region and a second oversampling region, respectively, and the length of the first oversampling region, the FOV region, and the second oversampling region in the preset direction is denoted as L1.

[0022] L1=L0+|th / tanα1|+|th / tanα2|;

[0023] Wherein, L0 is the size of the field of view (FOV) area in the preset direction, th is the initial layer thickness, α1 is the first tilt angle, and α2 is the second tilt angle.

[0024] In one implementation, the target layer thickness of the target selected layer is denoted as D, and is greater than the initial layer thickness of the initial selected layer;

[0025] If the radio frequency pulse is an excitation pulse, the selected layer thickness of the excitation selection layer corresponding to the excitation pulse is equal to D, and the selected layer thickness of the refocusing selection layer corresponding to the refocusing pulse is equal to the initial layer thickness of the initial selection layer.

[0026] If the radio frequency pulse is a refocusing pulse, the selected layer thickness of the refocusing selected layer corresponding to the refocusing pulse is equal to D, and the selected layer thickness of the excitation selected layer corresponding to the excitation pulse is equal to the initial layer thickness of the initial selected layer.

[0027] In one implementation, the first tilt angle is equal in magnitude to the second tilt angle, and the target layer thickness D is determined using the following formula:

[0028] D=(L0+|th / tan(-α)|)*|sin(-α)|

[0029] Where L0 is the field of view (FOV) size in the preset direction, th is the initial layer thickness, and α is the tilt angle.

[0030] In one implementation, the tilt of the target selection layer includes at least one of the following:

[0031] The tilted target selection layer did not cover the first edge field distortion region;

[0032] The tilted target selection layer did not cover the second edge field distortion region;

[0033] The second edge field distortion region and the first edge field distortion region are located at opposite ends of the imaging region, respectively.

[0034] In one implementation, obtaining the target magnetic resonance image based on the magnetic resonance data includes any of the following methods:

[0035] In the image domain, the first magnetic resonance image corresponding to the first magnetic resonance data and the second magnetic resonance image corresponding to the second magnetic resonance data are added or weighted and fused to obtain the target magnetic resonance image.

[0036] A first portion of the image, excluding fold artifacts, is extracted from the first magnetic resonance image, and a second portion of the image, excluding fold artifacts, is extracted from the second magnetic resonance image. The first portion of the image and the second portion of the image are then stitched together to obtain the target magnetic resonance image.

[0037] In one implementation, the tilt of the target selected layer relative to the initial selected layer is achieved using any of the following methods:

[0038] While applying an excitation pulse to the imaging region, a first layer selection gradient and the initial layer selection gradient are applied to the imaging region to tilt the first target layer selection; while applying an excitation pulse to the imaging region, a second layer selection gradient and the initial layer selection gradient are applied to the imaging region to tilt the second target layer selection.

[0039] While applying a refocusing pulse to the imaging region, a first layer selection gradient and the initial layer selection gradient are applied to the imaging region to tilt the first target layer selection; while applying a refocusing pulse to the imaging region, a second layer selection gradient and the initial layer selection gradient are applied to the imaging region to tilt the second target layer selection.

[0040] While applying an excitation pulse to the imaging region, a first layer selection gradient and the initial layer selection gradient are applied to the imaging region to tilt the first target layer selection; while applying a convergence pulse to the imaging region, a second layer selection gradient and the initial layer selection gradient are applied to the imaging region to tilt the second target layer selection.

[0041] While applying a refocusing pulse to the imaging region, a first layer selection gradient and the initial layer selection gradient are applied to the imaging region to tilt the first target layer selection; while applying an excitation pulse to the imaging region, a second layer selection gradient and the initial layer selection gradient are applied to the imaging region to tilt the second target layer selection.

[0042] This specification provides a magnetic resonance imaging device, the device comprising:

[0043] The FOV layer thickness determination module is used to determine the field of view (FOV) area and the initial layer thickness of the initial selected layer.

[0044] The layer selection gradient acquisition module is used to acquire the initial layer selection gradient based on the initial layer thickness;

[0045] The magnetic resonance data acquisition module is used to apply the initial layer selection gradient, the additional layer selection gradient, and the radio frequency pulse to the imaging region to excite the target layer selection and acquire the magnetic resonance data corresponding to the target layer selection; wherein, the target layer selection is tilted relative to the initial layer selection, and the tilted target layer selection covers the field of view (FOV) region.

[0046] A magnetic resonance image generation module is used to obtain a target magnetic resonance image based on the magnetic resonance data.

[0047] This specification provides a medical imaging device, which includes: a memory, and one or more processors communicatively connected to the memory; the memory stores instructions executable by the one or more processors, which, when executed by the one or more processors, cause the one or more processors to perform the steps of the method described in any of the above embodiments.

[0048] This specification provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method described in any of the above embodiments.

[0049] This specification provides a computer program product that includes instructions that, when executed by a processor of a computer device, enable the computer device to perform the steps of the method described in any of the above embodiments.

[0050] In the above-described embodiment, the field of view (FOV) and the initial layer thickness of the initial selected layer are determined; then, based on the initial layer thickness, the initial layer selection gradient is obtained; the initial layer selection gradient, an additional layer selection gradient, and a radio frequency pulse are applied to the imaging region to excite the target layer selection, which is tilted relative to the initial layer selection, and the tilted target layer selection covers the FOV; magnetic resonance data corresponding to the target layer selection is obtained; and a target magnetic resonance image is obtained based on the magnetic resonance data. By tilting the target layer selection, artifacts caused by edge field distortion are suppressed, and the tilted target layer selection covers the FOV, thus maintaining the FOV region unchanged, thereby improving the quality and signal-to-noise ratio of the magnetic resonance image. Attached Figure Description

[0051] Figure 1a This specification provides schematic diagrams illustrating application scenarios for the implementation of this method.

[0052] Figure 1b A schematic flowchart of the magnetic resonance imaging method provided in the embodiments of this specification;

[0053] Figure 2 A flowchart illustrating the determination of additional layer selection gradients provided for embodiments of this specification;

[0054] Figure 3 A schematic diagram of the edge field distortion location in the magnetic resonance imaging apparatus provided for the embodiments of this specification;

[0055] Figure 4 A flowchart illustrating the process of determining the layer selection gradient provided for the implementation of this specification;

[0056] Figure 5 A schematic diagram illustrating the tilting of the first target layer as provided in the embodiments of this specification;

[0057] Figure 6 A schematic diagram illustrating the tilting of the second target layer as provided in the embodiments of this specification;

[0058] Figure 7 A schematic flowchart of the magnetic resonance imaging method provided in the embodiments of this specification;

[0059] Figure 8 A schematic diagram of a magnetic resonance imaging apparatus provided for embodiments of this specification. Detailed Implementation

[0060] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0061] Magnetic Resonance Imaging (MRI) provides multi-parameter, multi-contrast image information. MRI can reflect various characteristics of biological tissues, such as T1, T2, and proton density-weighted values, and has become an indispensable tool in medical imaging and diagnosis. Due to the Zeeman effect, atomic nuclei with non-zero magnetic moments (hydrogen nuclei in the human body) undergo energy level splitting in a magnetic field, creating energy level differences. Radio frequency coils can excite hydrogen protons in the human body. When the electromagnetic wave energy of the radio frequency field equals the energy level difference of the atomic nuclei, resonance occurs, and the atomic nuclei transition from a lower energy level to a higher energy level. Then, a gradient field generated by a gradient coil is used for spatial encoding, and a receiving coil receives the electromagnetic signal of the selected location. Finally, Fourier transform is used to reconstruct the image information.

[0062] Fast spin echo (or Turbo spin echo) sequences are widely used rapid imaging sequences. They utilize multiple convergence pulses to generate a series of spin echoes, which are then phase-encoded and filled into the corresponding k-space. Fourier transform is then used to achieve magnetic resonance imaging (MRI). By varying the pulse repetition time (TR) and effective echo time (TE), fast spin echo sequences can obtain PD, T1, and T2-weighted images. Fast spin echo sequences are an important method for MRI vertex scanning.

[0063] Generally, phase encoding in MRI scans is set along the short axis because scanning along the short axis saves scan time and reduces phase artifacts. However, for sagittal vertebral scans, phase encoding can be set in the craniocaudal (FH) direction. Frequency encoding in the FH direction produces strong chemical shift artifacts. Due to the flow of cerebrospinal fluid, artifacts in the phase encoding direction negatively impact image quality, hindering diagnosis.

[0064] Due to the non-uniformity of the main magnetic field and gradient coil edges, significant marginal field distortion occurs when examining areas outside the field of view (FOV) on MRI. When the FOV is insufficient, artifacts caused by marginal field distortion will fold into the FOV, negatively impacting the image domain and hindering the doctor's diagnosis of the patient's condition.

[0065] In related technologies, wrinkling artifacts caused by edge field distortion can be reduced by expanding the field of view (FOV). Alternatively, artifacts caused by edge field distortion can be saturated by adding saturation bands at both ends of the FOV.

[0066] However, widening the field of view (FOV) reduces the resolution of magnetic resonance imaging (MRI) images, making clinical examinations of patients more difficult for doctors. Adding saturation bands at both ends of the FOV increases the specific absorption rate (SAR).

[0067] In related technologies, except for the limited area of ​​the isocenter region of an MRI magnet gradient device, the gradient system in almost all regions exhibits spatial nonlinearity, which is particularly severe at the magnet edges. At the magnet edges, in addition to edge field distortion, there is also coupling between the nonlinear gradient field and the main magnetic field. This coupling can cause the magnetic field strength far from the isocenter region to be approximately equal to the magnetic field strength near the isocenter, resulting in the signal resonance frequency in this region being the same as or very close to the signal resonance frequency near the isocenter. If the receiving coil receives a signal from this region, it will cause aliasing artifacts (CUSP artifacts) in the MRI image. In fast spin echo sequences, aliasing artifacts appear as a series of spots, stripes, or "feather-like" artifacts. While tilted excitation layer selection can suppress aliasing artifacts with constant slice thickness, it cannot completely solve the problem of folding artifacts caused by edge field distortion. Furthermore, tilted excitation layer selection can cause signal loss in some areas within the field of view (FOV), leading to a decrease in the signal-to-noise ratio of the MRI image.

[0068] Based on this, this specification provides a magnetic resonance imaging method that determines the field of view (FOV) and the initial slice thickness of the initial selected slice; then, based on the initial slice thickness, obtains the initial slice gradient; applies the initial slice gradient, an additional slice gradient, and a radio frequency pulse to the imaging region to excite the target slice, causing the target slice to tilt relative to the initial slice, and the tilted target slice covers the FOV; acquires the magnetic resonance data corresponding to the target slice; and obtains the target magnetic resonance image based on the magnetic resonance data. By tilting the target slice, artifacts caused by edge field distortion are suppressed, and the tilted target slice covers the FOV, thus maintaining the FOV region unchanged, thereby improving the quality and signal-to-noise ratio of the magnetic resonance image.

[0069] The methods described in this specification can be applied to magnetic resonance imaging (MRI) equipment. Artifacts caused by edge fields can be folding artifacts or flame-shaped artifacts. Please refer to... Figure 1a A magnetic resonance imaging (MRI) system comprises the following components: a magnet, gradient coils, and a radio frequency (RF) transmit coil. The spin of a hydrogen nucleus in the human body can be represented by a small magnetic needle. In the strong magnetic field provided by the magnet, the hydrogen nucleus transitions from a chaotic thermal equilibrium state to one where it is partially aligned with and partially against the main magnetic field. The difference between these two states forms the net magnetization vector. The hydrogen nucleus precesses around the main magnetic field, with the precession frequency proportional to the magnetic field strength. The RF transmit coil generates excitation and convergence pulses. The gradient coil generates slice-selective gradients. At the edges of the magnet (generating the B0 field) and the gradient coil (generating the gradient field), the MRI equipment produces edge field distortions aF and aH. aF is the location of the edge field distortion outside the field of view (FOV) in the foot direction, and aH is the location of the edge field distortion outside the field of view (FOV) in the head direction. Please continue reading... Figure 1a The function of a gradient power amplifier is to provide a linearly varying, low-ripple, and rapidly switching current to the gradient coil to generate a gradient magnetic field. A radio frequency (RF) power amplifier can be a device that amplifies the RF power generated by the oscillator in the emitter through a series of stages (excitation stage, intermediate stage, pre-amplifier stage, and final power amplification stage) to obtain sufficiently high RF power. The receiving unit can include an induction coil capable of sensing and generating detection signals and transmitting these signals. The coil interface unit can receive MRI signals through a coil conversion device. The RF control unit is connected to the RF transmitting coil and generates RF control signals based on the current position information to control the frequency and voltage of the RF signals emitted by the RF transmitting coil. The gradient control unit can be used to correct the gradient pulse shape. The bed control unit can be used to control the movement of the bed, allowing the patient to undergo multiple scans in different positions. The sequence control unit can be used to control the MRI sequence; different combinations of RF pulses and gradient pulses can form different MRI sequences, and different MRI sequences produce MRI images with their own characteristics.

[0070] This specification provides a magnetic resonance imaging method. Please refer to [link to relevant documentation]. Figure 1b The magnetic resonance imaging method may include the following steps:

[0071] S110. Determine the field of view (FOV) area and the initial layer thickness for the initial layer selection.

[0072] The size of the field of view (FOV) is related to the size of the examined area and should be selected under the guidance of a physician. The FOV is the actual area in magnetic resonance imaging (MRI), that is, the actual size of the image region in the frequency encoding and phase encoding directions. The FOV generally varies depending on the individual, the examined area, and the slice orientation. In principle, the FOV should be larger than the target area. A larger FOV results in larger imaging voxels, increased signal-to-noise ratio (SNR), and reduced artifacts, although spatial resolution may decrease. Target slice selection can be either excitation-selective or convergence-selective. Slice thickness determines the contrast and SNR of the MRI image. A thicker slice results in a stronger partial volumetric effect and a higher SNR. A thinner slice results in a weaker partial volumetric effect and higher inter-slice resolution. Slice thickness is positively correlated with pulse bandwidth and negatively correlated with gradient field strength; slice thickness can be controlled by adjusting bandwidth and field strength.

[0073] Specifically, the field of view (FOV) size can be determined based on the size of the inspected area. If the initial layer selection is excitation-selective layer selection, the layer thickness of the excitation-selective layer, i.e., the initial layer thickness of the initial layer selection, can be determined by the bandwidth of the excitation pulse and the layer selection gradient corresponding to the excitation pulse. If the initial layer selection is convergence-selective layer selection, the layer thickness of the convergence-selective layer, i.e., the initial layer thickness of the initial layer selection, can be determined by the bandwidth of the convergence pulse and the layer selection gradient corresponding to the convergence pulse.

[0074] S120. Based on the initial layer thickness, obtain the initial layer selection gradient.

[0075] The layer selection gradient refers to the rate of change of the magnetic field gradient during the scanning process. A larger layer selection gradient results in a faster scanning speed, but also a decrease in image resolution.

[0076] In some cases, physicians need to select appropriate slice thickness and slice gradient based on the specific situation to obtain high-quality images. Generally, a smaller slice thickness and a larger slice gradient can improve image resolution and clarity, but this also increases imaging time and radiation dose to the patient. Therefore, physicians need to strike a balance between image quality and patient safety, choosing the most suitable slice thickness and slice gradient. Thus, after determining the initial slice selection, an initial slice gradient can be determined based on considerations of image quality and patient safety.

[0077] S130. Apply an initial layer selection gradient, an additional layer selection gradient, and a radio frequency pulse to the imaging region to excite the target layer selection and acquire the magnetic resonance data corresponding to the target layer selection.

[0078] S140. Obtain the target magnetic resonance image based on the magnetic resonance data.

[0079] In this process, the target slice selection is tilted relative to the initial slice selection, and the tilted target slice covers the field of view (FOV). Additional slice selection gradients can be applied in any magnetic resonance imaging (MRI) direction other than the slice selection gradient direction corresponding to the initial slice selection gradient. MRI directions also include phase-encoding and frequency-encoding directions. The initial slice selection gradient determines the scanning slice location affected by the excitation and retraction pulses. MRI data can be used to generate MRI images. The target slice selection can be either excitation-selective or retraction-selective. The angle of the first tilt is opposite to that of the second tilt. Typically, artifacts caused by the edge field can affect diagnostic quality in some cases, while others may be confused with lesions, thus masking the true pathology.

[0080] In some cases, the target layer selection is tilted relative to the initial layer selection due to the combined effects of the initial layer selection gradient, the additional layer selection gradient, and the radio frequency pulse. The radio frequency pulse may include an excitation pulse and / or a refocusing pulse. Simultaneous excitation and refocusing layer selection are required for imaging. For the edge region at either end of the imaging area, tilting the target layer selection can prevent the excitation and refocusing layers from simultaneously selecting at least a portion of the edge region at that end.

[0081] Specifically, a localization image is obtained by scanning the target scanning area, and a magnetic resonance image is obtained by scanning the target scanning area. A radio frequency pulse is applied to the imaging region, and then an initial layer selection gradient is applied to the imaging region in the layer selection gradient direction to determine the target layer. Next, an additional layer selection gradient is applied to the imaging region. Under the combined action of the initial layer selection gradient, the additional layer selection gradient, and the radio frequency pulse, the target layer can be excited, causing the target layer to tilt relative to the initial layer selection. The tilted target layer can cover the field of view (FOV). The tilting of the initial layer selection ensures that at least some edge field distortion regions are not simultaneously selected by the excitation layer selection and the reconvergence layer selection, thereby suppressing artifacts caused by the edge field. Exciting the target layer allows the acquisition of the corresponding magnetic resonance data, and a target magnetic resonance image can be generated based on the magnetic resonance data.

[0082] In the aforementioned magnetic resonance imaging method, the field of view (FOV) and the initial slice thickness of the initial selected slice are determined. Then, based on the initial slice thickness, the initial slice gradient is obtained. The initial slice gradient, an additional slice gradient, and a radio frequency pulse are applied to the imaging region to excite the target slice. The target slice is tilted relative to the initial slice, and the tilted target slice covers the FOV. Magnetic resonance data corresponding to the target slice is acquired. The target magnetic resonance image is obtained based on the magnetic resonance data. By tilting the target slice, artifacts caused by edge field distortion are suppressed, and the tilted target slice covers the FOV, thus maintaining the FOV region unchanged, thereby improving the quality and signal-to-noise ratio of the magnetic resonance image.

[0083] In some implementations, please refer to Figure 2 The direction of the additional layer selection gradient is either the phase encoding direction or the frequency encoding direction; the determination of the additional layer selection gradient may include the following steps:

[0084] S210. Determine the tilt angle of the target layer.

[0085] S220. Determine the additional layer selection gradient based on the tilt angle and the initial layer selection gradient.

[0086] The tilt angle can be determined based on the location of distortion in the edge region and the degree of artifacts. The preset direction can be either the phase encoding direction or the frequency encoding direction.

[0087] In some cases, by applying an additional layer selection gradient, the target layer selection can be tilted. The tilting of the target layer can prevent the edge region from being covered or reduce the coverage of the edge region, causing the signal in the edge region to disappear or weaken.

[0088] Specifically, the tilt angle of the target layer selection can be determined based on the location of distortion in the edge region and the degree of artifacts. The additional layer selection gradient can be determined using the following formula:

[0089] α = arctan(Gps / Gss)

[0090] Where α is the tilt angle, Gss is the initial layer selection gradient, and Gps is the additional layer selection gradient. The additional layer selection gradient can be determined using the known initial layer selection gradient and the determined tilt angle. Then, the additional layer selection gradient can be applied in either the phase coding direction or the frequency coding direction.

[0091] In some implementations, the tilt angle A1 can be determined based on the location of the distortion in the edge region and the degree of artifacts. An additional layer selection gradient G1 can be determined using the known initial layer selection gradient and the tilt angle A1. Then, the additional layer selection gradient G1 can be applied in either the phase coding direction or the frequency coding direction. If the expected coverage effect in the edge region is not achieved after applying the additional layer selection gradient G1, the tilt angle A2 can be determined again based on the difference between the applied additional layer selection gradient G1 and the expected coverage effect, and the tilt angle A1. This process is repeated until the expected coverage effect in the edge region is achieved after applying the additional layer selection gradient.

[0092] In other implementations, based on experience accumulated during actual use, relationship data between tilt angle, distortion location, and artifact degree can be prepared. Based on the determined distortion location and artifact degree, a search can be performed in the relationship data to determine the tilt angle that matches the distortion location and artifact degree. By determining the tilt angle, the desired effect of covering the edge area can be achieved.

[0093] In the aforementioned magnetic resonance imaging method, the tilt angle of the target slice is determined, and an additional slice gradient is determined based on the tilt angle and the initial slice gradient. By determining the additional slice gradient, the target slice can be selected without covering the edge region, thus suppressing or eliminating artifacts in the edge region.

[0094] In some implementations, applying an initial slice selection gradient, an additional slice selection gradient, and a radio frequency pulse to the imaging region to excite the target slice selection and acquire the magnetic resonance data corresponding to the target slice selection may include:

[0095] Apply an initial layer selection gradient, a first layer selection gradient, and a radio frequency pulse to the imaging region to excite the first target layer selection and acquire the first magnetic resonance data corresponding to the first target layer selection; and / or

[0096] An initial layer selection gradient, a second layer selection gradient, and a radio frequency pulse are applied to the imaging region to excite the second target layer selection and acquire the second magnetic resonance data corresponding to the second target layer selection.

[0097] The tilt angle of the first target layer is opposite to that of the second target layer, and the magnetic resonance data corresponding to the target layer includes first magnetic resonance data and / or second magnetic resonance data. First magnetic resonance data. Second magnetic resonance data.

[0098] In some cases, the first target layer selection tilts under the combined effect of the first layer selection gradient, the initial layer selection gradient, and the radio frequency pulse. The second target layer selection tilts under the combined effect of the second layer selection gradient, the initial layer selection gradient, and the radio frequency pulse. The radio frequency pulse may include an excitation pulse and / or a refocusing pulse.

[0099] Specifically, a localization image is obtained by scanning the target scanning area, and a magnetic resonance image is obtained by scanning the target scanning area. A radio frequency (RF) pulse is applied to the imaging region, and then an initial slice selection gradient is applied to the imaging region in the slice selection gradient direction to determine the first target slice. If the RF pulse applied to the imaging region is an excitation pulse, the first target slice can be determined as an excitation slice. If the RF pulse applied to the imaging region is a refocusing pulse, the first target slice can be determined as a refocusing slice. Next, an additional first slice selection gradient is applied to the imaging region. Under the combined action of the first slice selection gradient, the initial slice selection gradient, and the RF pulse, the first target slice can be excited, and the first magnetic resonance data can be acquired. Exciting the first target slice can cause the first target slice to tilt.

[0100] Applying a radio frequency (RF) pulse to the imaging region, followed by applying an initial slice selection gradient in the slice selection gradient direction, determines the first target slice. If the RF pulse applied to the imaging region is an excitation pulse, the first target slice is determined as an excitation slice. If the RF pulse applied to the imaging region is a refocusing pulse, the first target slice is determined as a refocusing slice. Next, an additional second slice selection gradient is applied to the imaging region. Under the combined effect of the second slice selection gradient, the initial slice selection gradient, and the RF pulse, a second target slice can be excited, acquiring second magnetic resonance data. Exciting the second target slice can cause it to tilt in the opposite direction to the tilt of the first target slice.

[0101] For example, a sagittal scan of the target area is performed to obtain a localization image, and a sagittal scan of the target area is then performed to obtain a magnetic resonance image. The magnetic resonance image uses the FH direction as the phase encoding direction. Edge field (main magnetic field B0 and gradient field) distortions may occur at both ends outside the field of view (FOV). Please refer to [link to relevant documentation]. Figure 3 The locations of aF and aH can generate edge field distortion. When the field of view (FOV) is small, this can cause regions outside the FOV to fold or wrap around to the other side of the image. Further exemplarily, if the target selection layer is tilted clockwise, at least a portion of the aF region may not be selected by both the excitation and reconvergence layers simultaneously; if the target selection layer is tilted counterclockwise, at least a portion of the aH region may not be selected by both the excitation and reconvergence layers simultaneously, thereby suppressing artifacts caused by the edge field.

[0102] It should be noted that the field of view (FOV) has three directions: AP represents the forward / backward direction, FH represents the cephalopod direction, and RL represents the left / right direction. When performing a transverse MRI scan, the scanning range can be altered by adjusting the values ​​of AP or RL. When performing a horizontal scan of the target area, the MRI image can use the AP direction as the phase encoding direction. When performing a coronal scan of the target area, the MRI image can use the RL direction as the phase encoding direction.

[0103] In the aforementioned magnetic resonance imaging method, an initial slice selection gradient, a first slice selection gradient, and a radio frequency pulse are applied to the imaging region to excite a first target slice and acquire first magnetic resonance data corresponding to the first target slice; and / or an initial slice selection gradient, a second slice selection gradient, and a radio frequency pulse are applied to the imaging region to excite a second target slice and acquire second magnetic resonance data corresponding to the second target slice; wherein the tilt angle of the first target slice is opposite to that of the second target slice. By applying additional slice selection gradients to the imaging region, artifacts caused by edge fields can be suppressed, and either the first or second magnetic resonance data can be acquired.

[0104] In some implementations, please refer to Figure 4 The determination of the first and second layer-selection gradients may include the following steps:

[0105] S410. Determine the first tilt angle, and determine the first layer selection gradient based on the first tilt angle and the initial layer selection gradient.

[0106] S420. Determine the second tilt angle, and determine the second layer selection gradient based on the second tilt angle and the initial layer selection gradient.

[0107] The first tilt angle can be determined based on the location of the distortion in the first edge field distortion region and the degree of artifacts. The second tilt angle can be determined based on the location of the distortion in the second edge field distortion region and the degree of artifacts.

[0108] Specifically, the first tilt angle can be determined based on the location of the distortion in the first edge field distortion region and the degree of artifacts. The first layer selection gradient can be determined according to the following formula:

[0109] α1 = arctan(Gps1 / Gss)

[0110] Where α1 is the tilt angle for the first tilt, Gss is the initial layer selection gradient, and Gps1 is the first layer selection gradient. The first layer selection gradient can be determined using the known initial layer selection gradient and the determined first tilt angle. Then, the first layer selection gradient can be applied in either the phase coding direction or the frequency coding direction.

[0111] The second tilt angle can be determined based on the location of the distortion in the second edge field distortion region and the degree of artifacts. The second layer selection gradient can be determined using the following formula:

[0112] α² = arctan(Gps² / Gss)

[0113] Where α2 is the tilt angle of the second tilt, Gss is the initial layer selection gradient, and Gps2 is the second layer selection gradient. The second layer selection gradient can be determined using the known initial layer selection gradient and the determined second tilt angle. Then, the second layer selection gradient can be applied in either the phase coding direction or the frequency coding direction.

[0114] In the aforementioned magnetic resonance imaging method, a first tilt angle is determined, and a first slice selection gradient is determined based on the first tilt angle and the initial slice selection gradient. A second tilt angle is then determined, and a second slice selection gradient is determined based on the second tilt angle and the initial slice selection gradient. By determining an additional first or second slice selection gradient, the target slice is tilted when an additional slice selection gradient is subsequently applied, thereby suppressing artifacts.

[0115] In some implementations, the second tilt angle is equal in magnitude and opposite in direction to the first tilt angle. When applying a first or second layer selection gradient, while keeping the field of view (FOV) constant, the target layer thickness for the selected layer is determined based on the initial layer thickness, the first tilt angle, and the FOV size in a preset direction. The interlayer spacing between adjacent scanned layers is determined by the FOV size and the first tilt angle.

[0116] Please refer to Figure 3 In the diagram, "gap" represents the interlayer spacing of a magnetic resonance imaging (MRI) system. The interlayer spacing of an MRI system can be the hollow space between two layers with an original layer thickness of th; it contains gaps.

[0117] In some cases, artifacts caused by edge fields can be suppressed by keeping the field of view (FOV) constant. To keep the FOV constant, the initial layer thickness needs to be changed to obtain the target layer thickness.

[0118] Specifically, the second tilt angle is one of two tilt angles that are equal in magnitude and opposite in direction to the first tilt angle. While keeping the field of view (FOV) constant, a first layer selection gradient can be applied to the target layer selection. Then, the target layer thickness can be determined based on the data relationship between the initial layer thickness, the first tilt angle, and the FOV size in the preset direction. The interlayer spacing between adjacent scanned layers can be determined using the following formula:

[0119] gap=L0*tanα1

[0120] Where gap is the interlayer spacing between adjacent scan layers, L0 is the field of view (FOV) size in the preset direction, and α1 is the tilt angle of the first tilt.

[0121] While keeping the field of view (FOV) constant, a second layer selection gradient can be applied to the target layer. Then, based on the data relationship between the initial layer thickness, the second layer selection gradient, and the FOV size in the preset direction, the target layer thickness can be determined. The interlayer spacing between adjacent scanned layers can be determined using the following formula:

[0122] gap=L0*tanα2

[0123] Where gap is the interlayer spacing between adjacent scan layers, L0 is the field of view (FOV) size in the preset direction, and α2 is the tilt angle of the second tilt. The parameter oversampling factor can be determined according to the following formula:

[0124] OPE = (L1 / L0) * 100%

[0125] Where OPE is the oversampling factor, L0 is the field of view (FOV) size in the preset direction, and L1 is the length of the first oversampling region, the field of view (FOV), and the second oversampling region in the preset direction.

[0126] In some embodiments, the two ends of the field of view (FOV) region have a first oversampled region and a second oversampled region, respectively, and the length of the first oversampled region, the FOV region, and the second oversampled region in a preset direction is denoted as L1;

[0127] L1=L0+|th / tanα1|+|th / tanα2|;

[0128] Where L0 is the size of the field of view (FOV) area in the preset direction, th is the initial layer thickness, α1 is the tilt angle of the first tilt, and α2 is the tilt angle of the second tilt.

[0129] For example, please refer to Figure 5 In the diagram, the lengths of the first oversampled region 510, the field of view (FOV) region 520, and the second oversampled region 530 in the preset direction can be denoted as L1. The length of the FOV region 520 in the preset direction can be denoted as L0. Region 1 is the original FOV region. The rectangular region represents the location of the FOV region of the second layer. The solid triangle represents the oversampled region.

[0130] In the above magnetic resonance imaging method, by determining the length of the first oversampling region, the field of view (FOV), and the second oversampling region in a preset direction and denoting it as L1, it can be ensured that the region covers both ends of the FOV, thereby suppressing artifacts caused by the edge field or preventing the medical image from producing folding artifacts.

[0131] In some implementations, the target layer thickness of the target layer is denoted as D, and is greater than the initial layer thickness of the initial layer selection.

[0132] If the RF pulse is an excitation pulse, the selected layer thickness of the excitation layer corresponding to the excitation pulse is equal to D, and the selected layer thickness of the refocusing layer corresponding to the refocusing pulse is equal to the initial layer thickness of the initial selected layer.

[0133] If the RF pulse is a refocusing pulse, the selected layer thickness of the refocusing layer corresponding to the refocusing pulse is equal to D, and the selected layer thickness of the excitation layer corresponding to the excitation pulse is equal to the initial layer thickness of the initial selected layer.

[0134] In some cases, artifacts caused by edge fields can be suppressed while keeping the field of view (FOV) constant. While keeping the FOV constant, the target layer thickness for the selected layer can be determined to be greater than the initial layer thickness of the initial layer selection based on the data relationship between the FOV size, initial layer thickness, and tilt angle in a preset direction.

[0135] Specifically, if the radio frequency pulse is an excitation pulse, the selected layer thickness D of the excitation layer can be determined based on the data relationship between the field of view (FOV) size, initial layer thickness, and tilt angle in the preset direction, while the selected layer thickness of the refocusing layer corresponding to the refocusing pulse is equal to the initial layer thickness of the initial selected layer. If the radio frequency pulse is a refocusing pulse, the selected layer thickness D of the refocusing layer corresponding to the refocusing pulse can be determined based on the data relationship between the field of view (FOV) size, initial layer thickness, and tilt angle in the preset direction, while the selected layer thickness of the excitation layer corresponding to the excitation pulse is equal to the initial layer thickness of the initial selected layer.

[0136] In some implementations, the first tilt angle and the second tilt angle are equal in magnitude, and the target layer thickness D is determined using the following formula:

[0137] D=(L0+|th / tan(-α)|)*|sin(-α)|

[0138] Where L0 is the field of view (FOV) size in the preset direction, th is the initial layer thickness, and α is the tilt angle.

[0139] In some cases, while keeping the field of view (FOV) constant, the target layer thickness can be determined based on the data relationship between the FOV size, initial layer thickness, and tilt angle in a preset direction. By keeping the FOV size constant, artifacts caused by edge fields can be suppressed.

[0140] In some implementations, the tilting of the target selection layer includes at least one of the following:

[0141] The tilted target selection layer did not cover the first edge field distortion region;

[0142] The tilted target selection layer did not cover the second edge field distortion region.

[0143] The second edge field distortion region and the first edge field distortion region are located at opposite ends of the imaging region, respectively.

[0144] In some cases, the edge field distortion region can only generate a signal when it is selected by both refocusing and excitation selection.

[0145] Specifically, please refer to Figure 5 , Figure 5 In this context, aF represents the first edge field distortion region. Figure 5 aH in the diagram represents the second edge field distortion region. Please refer to the following: Figure 5 The target layer selection tilt angle is α. The tilted target layer selection does not cover the first edge field distortion region aF. Therefore, the first edge field distortion region aF may not be selected simultaneously by both excitation layer selection and refocusing layer selection. Please refer to... Figure 6 , Figure 6 In this context, aF represents the first edge field distortion region. Figure 6 aH in the diagram represents the second edge field distortion region. Please refer to the following: Figure 6 The tilt angle of the target selection layer is -α. The tilted target selection layer does not cover the second edge field distortion region aH. The second edge field distortion region aH can be completely left unselected by both excitation selection and re-convergence selection.

[0146] In the above magnetic resonance imaging method, the tilted target selection layer does not cover the first edge field distortion region; the tilted target selection layer does not cover the second edge field distortion region; the target selection layer does not cover the edge region, which can suppress artifacts in the edge region.

[0147] In some implementations, a target magnetic resonance image is obtained based on magnetic resonance data, including any of the following methods:

[0148] In the image domain, the first magnetic resonance image corresponding to the first magnetic resonance data and the second magnetic resonance image corresponding to the second magnetic resonance data are added or weighted and fused to obtain the target magnetic resonance image.

[0149] A first portion of the image, excluding fold artifacts, is extracted from the first magnetic resonance image. A second portion of the image, excluding fold artifacts, is extracted from the second magnetic resonance image. The first and second portions of the image are then stitched together to obtain the target magnetic resonance image.

[0150] In this process, after acquiring the image, the folded region is calculated based on the difference in the field of view (FOV) between the two images. The human tissue structure in the folded region is obtained from the positioning image. The folded region is the display area of ​​the human tissue structure that has been folded onto the magnetic resonance image on the positioning image.

[0151] In some implementations, a first magnetic resonance image can be generated based on the first magnetic resonance data. A second magnetic resonance image can be generated based on the second magnetic resonance data. Please refer to [link to relevant documentation]. Figure 5 It can be determined Figure 5 The overlapping portion 540 between the tilted target layer and the initial layer is preserved. The edge field distortion aH of the overlapping portion 540 and the second edge field distortion region aH is retained. The artifacts caused by the distortion at the aH location reduce the signal intensity in the magnetic resonance image. Please refer to Figure 6 It can be determined Figure 6 The target layer, which is tilted, overlaps with the initial layer in a portion 610. The edge field distortion aF of the overlapping portion 610 and the first edge region aF is preserved. The artifacts caused by the distortion at position aF have reduced signal intensity in the magnetic resonance image. Adding the first magnetic resonance image corresponding to the first magnetic resonance data and the second magnetic resonance image corresponding to the second magnetic resonance data in the image domain allows the preserved edge field distortion aF to be added to the edge field distortion aH, resulting in the target magnetic resonance image. The preserved region in the target magnetic resonance image can suppress folding artifacts. Alternatively, weighted fusion of the first magnetic resonance image corresponding to the first magnetic resonance data and the second magnetic resonance image corresponding to the second magnetic resonance data in the image domain allows the preserved edge field distortion aF to be added to the edge field distortion aH in a weighted manner, resulting in the target magnetic resonance image. The preserved region in the target magnetic resonance image can suppress folding artifacts.

[0152] In other implementations, please refer to Figure 5 The first edge field distortion region aF can be completely unselected by both excitation-based and refocus-based layer selection, therefore the obtained first magnetic resonance image does not contain the folding artifacts caused by aF distortion. (See also...) Figure 6 The second edge field distortion region aH can be completely excluded from both excitation-selection and reconvergence-selection, thus the obtained second magnetic resonance image does not contain folding artifacts caused by aH distortion. A first portion of the image excluding folding artifacts is extracted from the first magnetic resonance image, and a second portion of the image excluding folding artifacts is extracted from the second magnetic resonance image. The first and second portions are then stitched together to obtain the target magnetic resonance image, which does not contain folding artifacts.

[0153] In the above-mentioned magnetic resonance imaging method, the first magnetic resonance image corresponding to the first magnetic resonance data and the second magnetic resonance image corresponding to the second magnetic resonance data are added or weighted and fused in the image domain to obtain the target magnetic resonance image. Alternatively, a first part of the image that does not contain folding artifacts can be extracted from the first magnetic resonance image and a second part of the image that does not contain folding artifacts can be extracted from the second magnetic resonance image. The target magnetic resonance image is obtained by stitching the first part of the image and the second part of the image together. This method can suppress folding artifacts.

[0154] In some implementations, the target layer selection is tilted relative to the initial layer selection using any of the following methods:

[0155] While applying an excitation pulse to the imaging region, a first layer selection gradient and an initial layer selection gradient are applied to the imaging region to tilt the first target layer selection; while applying an excitation pulse to the imaging region, a second layer selection gradient and an initial layer selection gradient are applied to the imaging region to tilt the second target layer selection.

[0156] While applying a retraction pulse to the imaging region, a first layer selection gradient and an initial layer selection gradient are applied to the imaging region to tilt the first target layer selection; while applying a retraction pulse to the imaging region, a second layer selection gradient and an initial layer selection gradient are applied to the imaging region to tilt the second target layer selection.

[0157] While applying an excitation pulse to the imaging region, a first layer selection gradient and an initial layer selection gradient are applied to the imaging region to tilt the first target layer selection; while applying a retraction pulse to the imaging region, a second layer selection gradient and an initial layer selection gradient are applied to the imaging region to tilt the second target layer selection.

[0158] While applying a refocusing pulse to the imaging region, a first layer selection gradient and an initial layer selection gradient are applied to the imaging region to tilt the first target layer selection; while applying an excitation pulse to the imaging region, a second layer selection gradient and an initial layer selection gradient are applied to the imaging region to tilt the second target layer selection.

[0159] In this embodiment, the first target layer selection can be an excitation layer selection. While applying an excitation pulse to the imaging region, a first layer selection gradient and an initial layer selection gradient are applied to the imaging region. Based on the first layer selection gradient and the initial layer selection gradient, the first target layer selection can be excited, causing it to tilt, and the convergence layer selection returns to its original position. The second target layer selection can also be an excitation layer selection. A second layer selection gradient and an initial layer selection gradient are applied to the imaging region. Based on the second layer selection gradient and the initial layer selection gradient, the second target layer selection can be excited, causing it to tilt, and the convergence layer selection returns to its original position.

[0160] In this embodiment, the first target layer selection can be a convergence layer selection. While applying a convergence pulse to the imaging region, a first layer selection gradient and an initial layer selection gradient are applied to the imaging region. Based on the first layer selection gradient and the initial layer selection gradient, the first target layer can be activated, causing it to tilt and remain in its original position. The second target layer selection can also be a convergence layer selection. A second layer selection gradient and an initial layer selection gradient are applied to the imaging region. Based on the second layer selection gradient and the initial layer selection gradient, the second target layer can be activated, causing it to tilt and remain in its original position.

[0161] In this embodiment, the first target layer selection can be an excitation layer selection. While applying an excitation pulse to the imaging region, a first layer selection gradient and an initial layer selection gradient are applied to the imaging region. Based on the first layer selection gradient and the initial layer selection gradient, the first target layer selection can be excited, causing it to tilt, while the convergence layer selection remains in its original position. The second target layer selection can be a convergence layer selection. While applying a convergence pulse to the imaging region, a second layer selection gradient and an initial layer selection gradient are applied to the imaging region. Based on the second layer selection gradient and the initial layer selection gradient, the second target layer selection can be excited, causing it to tilt, while the excitation layer selection remains in its original position.

[0162] In this embodiment, the first target layer selection can be a convergence layer selection. While applying a convergence pulse to the imaging region, a first layer selection gradient and an initial layer selection gradient are applied to the imaging region. Based on the first layer selection gradient and the initial layer selection gradient, the first target layer selection can be excited, causing it to tilt, and the excited layer selection remains in its original position. The second target layer selection can be an excitation layer selection. While applying an excitation pulse to the imaging region, a second layer selection gradient and an initial layer selection gradient are applied to the imaging region. Based on the second layer selection gradient and the initial layer selection gradient, the second target layer selection can be excited, causing it to tilt, and the convergence layer selection remains in its original position.

[0163] In the aforementioned magnetic resonance imaging method, while applying a pulse to the imaging region, a slice selection gradient corresponding to the pulse and an initial slice selection gradient are also applied to the imaging region. This causes the target slice selection to tilt, resulting in either a portion of the edge field distortion region not selected by both the excitation slice selection and the convergence slice selection, or the entire edge field distortion region not selected by both excitation slice selection and the convergence slice selection. If only a portion of the edge field distortion region is not selected by both excitation slice selection and the convergence slice selection, artifacts within the edge field distortion region can be suppressed. If the entire edge field distortion region is not selected by both excitation slice selection and the convergence slice selection, artifacts within the edge field distortion region can be eliminated.

[0164] This specification also provides a magnetic resonance imaging method, for example, please refer to [link to relevant documentation]. Figure 7 The magnetic resonance imaging method may include the following steps:

[0165] S702. Determine the field of view (FOV) area and the initial layer thickness for the initial layer selection.

[0166] S704. Based on the initial layer thickness, obtain the initial layer selection gradient.

[0167] S706. Determine the first tilt angle, and determine the first layer selection gradient based on the first tilt angle and the initial layer selection gradient.

[0168] S708. Apply an initial layer selection gradient, a first layer selection gradient, and a radio frequency pulse to the imaging region to excite the first target layer selection and acquire the first magnetic resonance data corresponding to the first target layer selection.

[0169] S710. Determine the second tilt angle, and determine the second layer selection gradient based on the second tilt angle and the initial layer selection gradient.

[0170] The direction of the first tilt angle is opposite to the direction of the second tilt angle.

[0171] S712. Apply an initial layer selection gradient, a second layer selection gradient, and a radio frequency pulse to the imaging region to excite the second target layer selection and acquire the second magnetic resonance data corresponding to the second target layer selection.

[0172] The tilt angle of the first target layer is opposite to that of the second target layer.

[0173] S714. In the image domain, perform an addition operation or weighted fusion on the first magnetic resonance image corresponding to the first magnetic resonance data and the second magnetic resonance image corresponding to the second magnetic resonance data to obtain the target magnetic resonance image.

[0174] This specification provides a magnetic resonance imaging device 800. Please refer to [link / reference]. Figure 8 The magnetic resonance imaging device 800 includes: an FOV layer thickness determination module 810, a layer gradient acquisition module 820, a magnetic resonance data acquisition module 830, and a magnetic resonance image generation module 840.

[0175] The FOV layer thickness determination module 810 is used to determine the field of view (FOV) area and the initial layer thickness of the initial selected layer.

[0176] The layer selection gradient acquisition module 820 is used to acquire the initial layer selection gradient based on the initial layer thickness;

[0177] The magnetic resonance data acquisition module 830 is used to apply the initial layer selection gradient, the additional layer selection gradient, and the radio frequency pulse to the imaging region to excite the target layer selection and acquire the magnetic resonance data corresponding to the target layer selection; wherein, the target layer selection is tilted relative to the initial layer selection, and the tilted target layer selection covers the field of view (FOV) region.

[0178] The magnetic resonance image generation module 840 is used to obtain a target magnetic resonance image based on the magnetic resonance data.

[0179] For a detailed description of the magnetic resonance imaging device, please refer to the description of the magnetic resonance imaging method above, which will not be repeated here.

[0180] In some embodiments, a medical imaging device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the method steps described above.

[0181] This specification provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method in any of the above embodiments.

[0182] One embodiment of this specification provides a computer program product including instructions that, when executed by a processor of a computer device, enable the computer device to perform the steps of the method described in any of the above embodiments.

[0183] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which programs can be printed, because programs can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

Claims

1. A magnetic resonance imaging method, characterized in that, The method includes: Determine the field of view (FOV) area and the initial layer thickness for initial layer selection; Based on the initial layer thickness, obtain the initial layer selection gradient; An initial layer selection gradient, an additional layer selection gradient, and a radio frequency pulse are applied to the imaging region to excite the target layer selection and acquire the magnetic resonance data corresponding to the target layer selection. The direction of the additional layer selection gradient is either the phase encoding direction or the frequency encoding direction. The target layer selection is tilted relative to the initial layer selection, and the tilted target layer selection covers the field of view (FOV). The tilt of the target layer selection includes at least one of the following: the tilted target layer selection does not cover the first edge field distortion region; the tilted target layer selection does not cover the second edge field distortion region; wherein the second edge field distortion region and the first edge field distortion region are located at opposite ends of the imaging region. The target magnetic resonance image is obtained based on the magnetic resonance data.

2. The method according to claim 1, characterized in that, The method for determining the additional layer selection gradient includes: Determine the tilt angle of the target selected layer; The additional layer selection gradient is determined based on the tilt angle and the initial layer selection gradient.

3. The method according to claim 1, characterized in that, The process of applying the initial layer-selection gradient, the additional layer-selection gradient, and the radio frequency pulse to the imaging region to excite the target layer selection and acquire the magnetic resonance data corresponding to the target layer selection includes: The initial layer selection gradient, the first layer selection gradient, and the radio frequency pulse are applied to the imaging region to excite the first target layer selection and acquire the first magnetic resonance data corresponding to the first target layer selection; and / or An initial layer selection gradient, a second layer selection gradient, and a radio frequency pulse are applied to the imaging region to excite a second target layer selection and acquire the second magnetic resonance data corresponding to the second target layer selection; wherein, the tilt angle of the first target layer selection is opposite to that of the second target layer selection, and the magnetic resonance data corresponding to the target layer selection includes the first magnetic resonance data and / or the second magnetic resonance data.

4. The method according to claim 3, characterized in that, The methods for determining the first and second layer-selection gradients include: Determine a first tilt angle, and determine the first layer selection gradient based on the first tilt angle and the initial layer selection gradient; Determine the second tilt angle, and determine the second layer selection gradient based on the second tilt angle and the initial layer selection gradient.

5. The method according to claim 4, characterized in that, The second tilt angle is equal in magnitude to the first tilt angle but opposite in direction; When the first layer selection gradient or the second layer selection gradient is applied, the field of view (FOV) size remains unchanged, and the target layer thickness of the target layer is determined based on the initial layer thickness, the first tilt angle, and the FOV size in the preset direction. The interlayer spacing between adjacent scanning layers is determined by the field of view (FOV) size and the first tilt angle.

6. The method according to claim 4, characterized in that, The field of view (FOV) region has a first oversampling region and a second oversampling region at its two ends, and the length of the first oversampling region, the FOV region, and the second oversampling region in a preset direction is denoted as L1. L1=L0+|th / tanα1|+|th / tanα2|; Wherein, L0 is the size of the field of view (FOV) area in the preset direction, th is the initial layer thickness, α1 is the first tilt angle, and α2 is the second tilt angle.

7. The method according to claim 2, characterized in that, The target layer thickness of the target selected layer is denoted as D, and it is greater than the initial layer thickness of the initial selected layer. If the radio frequency pulse is an excitation pulse, the selected layer thickness of the excitation selection layer corresponding to the excitation pulse is equal to D, and the selected layer thickness of the refocusing selection layer corresponding to the refocusing pulse is equal to the initial layer thickness of the initial selection layer. If the radio frequency pulse is a refocusing pulse, the selected layer thickness of the refocusing selected layer corresponding to the refocusing pulse is equal to D, and the selected layer thickness of the excitation selected layer corresponding to the excitation pulse is equal to the initial layer thickness of the initial selected layer.

8. The method according to claim 7, characterized in that, The first tilt angle and the second tilt angle are equal in magnitude, and the target layer thickness D is determined using the following formula: D=(L0+|th / tan(-α)|) |sin(-a)| Where L0 is the field of view (FOV) size in the preset direction, th is the initial layer thickness, and α is the tilt angle.

9. The method according to claim 3, characterized in that, The method of obtaining the target magnetic resonance image based on the magnetic resonance data includes any one of the following: In the image domain, the first magnetic resonance image corresponding to the first magnetic resonance data and the second magnetic resonance image corresponding to the second magnetic resonance data are added or weighted and fused to obtain the target magnetic resonance image. A first portion of the image, excluding fold artifacts, is extracted from the first magnetic resonance image, and a second portion of the image, excluding fold artifacts, is extracted from the second magnetic resonance image. The first portion of the image and the second portion of the image are then stitched together to obtain the target magnetic resonance image.

10. The method according to claim 1, characterized in that, The tilt of the target layer relative to the initial layer can be achieved using any of the following methods: While applying an excitation pulse to the imaging region, a first layer selection gradient and the initial layer selection gradient are applied to the imaging region to tilt the first target layer selection; while applying an excitation pulse to the imaging region, a second layer selection gradient and the initial layer selection gradient are applied to the imaging region to tilt the second target layer selection. While applying a refocusing pulse to the imaging region, a first layer selection gradient and the initial layer selection gradient are applied to the imaging region to tilt the first target layer selection; while applying a refocusing pulse to the imaging region, a second layer selection gradient and the initial layer selection gradient are applied to the imaging region to tilt the second target layer selection. While applying an excitation pulse to the imaging region, a first layer selection gradient and the initial layer selection gradient are applied to the imaging region to tilt the first target layer selection; while applying a convergence pulse to the imaging region, a second layer selection gradient and the initial layer selection gradient are applied to the imaging region to tilt the second target layer selection. While applying a refocusing pulse to the imaging region, a first layer selection gradient and the initial layer selection gradient are applied to the imaging region to tilt the first target layer selection; while applying an excitation pulse to the imaging region, a second layer selection gradient and the initial layer selection gradient are applied to the imaging region to tilt the second target layer selection.

11. A magnetic resonance imaging device, characterized in that, The device includes: The FOV layer thickness determination module is used to determine the field of view (FOV) area and the initial layer thickness of the initial selected layer. The layer selection gradient acquisition module is used to acquire the initial layer selection gradient based on the initial layer thickness; A magnetic resonance data acquisition module is used to apply the initial layer selection gradient, the additional layer selection gradient, and the radio frequency pulse to the imaging region to excite the target layer selection and acquire the magnetic resonance data corresponding to the target layer selection; wherein, the direction of the additional layer selection gradient is the phase encoding direction or the frequency encoding direction, the target layer selection is tilted relative to the initial layer selection, and the tilted target layer selection covers the field of view (FOV) region, the tilt of the target layer selection includes at least one of the following: the tilted target layer selection does not cover the first edge field distortion region; the tilted target layer selection does not cover the second edge field distortion region; wherein, the second edge field distortion region and the first edge field distortion region are respectively located at both ends of the imaging region; A magnetic resonance image generation module is used to obtain a target magnetic resonance image based on the magnetic resonance data.

12. A medical imaging device, comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 10.

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

Images