WO2023092319A1 - Magnetic resonance multi contrast-ratio parameter imaging method based on wave-type gradient - Google Patents
Magnetic resonance multi contrast-ratio parameter imaging method based on wave-type gradient Download PDFInfo
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- the invention relates to the technical field of medical image analysis, and more particularly, to a wave-like gradient-based magnetic resonance multi-contrast parameter imaging method.
- Magnetic resonance imaging Magnetic Resonance Imaging, MRI
- MRI Magnetic Resonance Imaging
- the protons in the target After the application of radio frequency pulses is stopped, the protons in the target generate magnetic resonance MR signals during the relaxation process, and the usable MR signals can be obtained through the processing of the MR signal reception, spatial encoding and image reconstruction. Since each signal contains full-layer information during the magnetic resonance process, it is necessary to perform spatial positioning encoding on the magnetic resonance signal, namely frequency encoding and phase encoding.
- the MR signal collected by the receiving coil is actually a radio wave with space-encoded information, which is an analog signal, it needs to be transformed into digital information through analog-to-digital conversion, and then the digital information is filled into the k-space, and finally the corresponding Digital dot matrix.
- k-space is closely related to the spatial positioning of magnetic resonance signals. This k-space is also called Fourier space, which is the filling space of the original digital information of MR signals with spatial positioning coding information.
- Each MR image has its corresponding k-space data lattice.
- the spatial positioning coding information in the original digital data can be decoded, and different frequencies, phases and For the MR signal of the amplitude, different frequencies and phases represent different spatial positions, and the amplitude represents the MR signal intensity.
- the MR digital signals of different frequencies, phases and signal strengths are allocated to the corresponding pixels to obtain MR image data, that is, to reconstruct the MR image.
- Fourier transform is the process of transforming the original data lattice of k-space into MR image lattice.
- Magnetic resonance parallel imaging method is a kind of method to accelerate the scanning speed of MRI, such as simultaneous acquisition of spatial harmonics technology (SMASH, simultaneous acquisition of spatial harmonics), sensitivity encoding technology (SENSE, sensitivity encoding) and overall automatic calibration partial parallel acquisition technology ( GRAPPA, generalized autocalibrating partially parallel acquisitions), etc.
- This type of method achieves the purpose of fast scanning by reducing the amount of collected data and using the redundant information contained in the multi-channel coil to reconstruct the under-sampled data.
- parallel imaging has been used to speed up various MRI sequences with multiple receive coils, and some improvements exist to achieve higher acceleration factors, for example, simultaneous multislice (SMS) imaging, controlled Hybrid acceleration technology (CAIPIRINHA), beam spotting phase encoding technology (BPE), controlled aliasing technology in volume parallel imaging (2D CAIPIRINHA), controlled mixing acceleration technology in wave-like gradient in volume parallel imaging (Wave- CAIPI) and so on.
- SMS simultaneous multislice
- CAIPIRINHA controlled Hybrid acceleration technology
- BPE beam spotting phase encoding technology
- 2D CAIPIRINHA controlled aliasing technology in volume parallel imaging
- Wave- CAIPI wave-like gradient in volume parallel imaging
- the purpose of the present invention is to overcome the above-mentioned defective of prior art, provide a kind of magnetic resonance multi-contrast parameter imaging method based on wave type gradient, to reduce the total scan time of the magnetic resonance parameter imaging of multi-contrast in clinical application, improve scanning process. Patient discomfort and risk of exercise.
- the technical solution of the present invention is to provide a wave-like gradient-based magnetic resonance multi-contrast parameter imaging method, comprising the following steps: acquiring a magnetic resonance imaging sequence, the sequence includes double repetition time, double flip angle, and each repetition time includes A plurality of echoes; when applying a readout gradient to the magnetic resonance imaging sequence, the magnetic resonance gradient field coil is used to apply a cosine wave gradient sequence in the layer selection direction, and a sine wave gradient sequence is applied in the phase direction; or a cosine wave is applied in the phase direction A wave gradient sequence, applying a sinusoidal wave gradient sequence in the layer selection direction; applying the wave gradient sequence to a gradient refocusing echo imaging sequence, and under-sampling the signal to obtain a multi-layer image, and then based on the multi-layer image , to obtain parametric images of various contrasts.
- the present invention has the advantage that it can realize high-magnification accelerated scanning while reducing the geometric factor g-factor and avoiding the generation of artifacts; compared with the existing Wave-CAIPI technology, the imaging proposed by the present invention The method solves the problem that one scan of Wave-CAIPI technology can only produce a single contrast image, and can obtain multiple contrast parameter images in a single scan, and significantly shortens the scanning time of contrast parameter imaging.
- FIG. 1 is a schematic diagram of an MRI sequence acquisition scheme according to an embodiment of the present invention
- Fig. 2 is a schematic diagram of readout gradient RO, cosine wave gradient CO, sine wave gradient SI and sampling template in k-space in a magnetic resonance imaging sequence according to an embodiment of the present invention
- Fig. 3 is a schematic diagram of an image processing pipeline of a magnetic resonance imaging sequence according to an embodiment of the present invention.
- Fig. 4 is a schematic diagram of a parametric image of a 4-fold accelerated multi-contrast obtained by one magnetic resonance imaging sequence scan according to an embodiment of the present invention.
- the invention provides a magnetic resonance fast imaging method based on wave-like gradient and gradient refocusing echo imaging (GRE) sequence, the sequence adopts wave-like gradient, double TR (repetition time), double flip angle (FA) and multiple
- GRE wave-like gradient and gradient refocusing echo imaging
- the wave design can be used for three-dimensional high-resolution multi-contrast MRI rapid parametric imaging, also known as WAMP imaging (Wave-CAIPI MULTIPLEX, WAMP for short).
- the present invention is based on Wave-CAIPI technology (“Wave-CAIPI for highly accelerated 3D imaging”, Magn Reson Med, June 2015; 73(6):2152-62; Bilgic B, et al.) and MULTIPLEX (“MULTI- parametric MR imaging with fLEXible design (MULTIPLEX)", Magn Reson Med, 2021 August 31. doi:10.1002/mrm.28999; Ye Y, et al.) technology to achieve ultra-fast imaging method with multiple contrast parameters, which can realize a A solution for multi-contrast parametric images acquired in a single scan.
- the technical solution of the present invention includes:
- the magnetic resonance gradient field coil While acquiring signals in a three-dimensional magnetic resonance imaging sequence (while applying a readout gradient), the magnetic resonance gradient field coil is used to apply a cosine wave gradient sequence in the layer selection direction (or phase direction). At the same time, apply a sinusoidal wave gradient sequence in the phase direction (or layer selection direction);
- step (3) applying the technical method described in step (1) and (2) to the three-dimensional WAMP sequence, and by constructing a signal model and image processing technology, obtaining parameter images of multiple contrasts, including B 1t image, T 1 image, T 2 image, T 1 weighted (T 1 W) image, enhanced T 1 weighted T 1 W (aT 1 W) image, T 2 weighted (T 2 W) image, enhanced T 2 weighted T 2 W (aT 2 W) images, T2* (T2*) images, proton density (PD) images, proton density-weighted (PDW) images, susceptibility-weighted imaging (SWI) images, and quantitative susceptibility mapping (QSM) images, and magnetic resonance angiography (MRA ) and other images.
- B 1t image T 1 image, T 2 image, T 1 weighted (T 1 W) image, enhanced T 1 weighted T 1 W (aT 1 W) image, T 2 weighted (T 2 W) image, enhanced T 2 weighted T 2 W (a
- the WAMP imaging sequence has double repetition time (TR), double flip angle (FA) (including ⁇ 1 and ⁇ 2 ) and multi-echo design.
- TR double repetition time
- FA double flip angle
- the dual TR comprising TR 1 and TR 2
- features are derived from the actual flip angle imaging (AFI) technique for B 1 t mapping.
- Acq 1 (corresponding to the upper part of the acquisition process module in Figure 1, or called the first acquisition module)
- Acq 2 (corresponding to the lower part of the acquisition process module in Figure 1, or called the second acquisition module) each contain a (AFI) Technology similar dual TR unit.
- a certain number (ie N 1 and N 2 ) of gradient echoes are acquired.
- Flow Modulation (FM) blocks can be inserted flexibly.
- Each acquisition module (Acq) uses a different flip angle (eg ⁇ 1 / ⁇ 2 ), each TR module has a different number of echoes and/or a different FM function (including on/off status).
- there is a corresponding readout gradient RO in the frequency encoding direction at each echo (RO and Acq are triggered simultaneously), a cosine wave gradient CO is applied in the layer selection encoding direction (or phase direction), and a cosine wave gradient CO is applied in the phase encoding direction ( Or select layer encoding direction) apply sinusoidal wave gradient SI.
- the gradient pulses of RO, CO, and SI in the WAMP imaging sequence, and the template sampled in k-space are under-sampled using the rule of every row and every column, as shown in Figure 2, where Figure 2(a) is the gradient Waveforms, Figure 2(b) is a sampling example, and Figure 2(c) is a k-space trajectory.
- Figure 2(a) is the gradient Waveforms
- Figure 2(b) is a sampling example
- Figure 2(c) is a k-space trajectory.
- a WAMP sequence scan can generate 2 (N 1 +N 2 ) echo image sets.
- a Flow Modulation (FM) block can be optionally inserted after each excitation pulse.
- the processing pipeline of the data image scanned by WAMP sequence is shown in Figure 3.
- WAMP data images as an example divided into four layers (Tier-0, Tier-1, Tier-2, and Tier-3), depending on their calculation order and relationship in the processing pipeline, and adopt multi-dimensional integration (MDI) concept for high signal-to-noise ratio (SNR), high fidelity and efficient complex image processing.
- MDI multi-dimensional integration
- the Tire-0 layer image is collected data from each k-space through the Wave-CAIPI signal, using the linear equation of the SENSE model to solve, and obtains 2 (N 1 +N 2 ) groups of "original” echo images; the Tire-1 layer image is the 2(N 1 +N 2 ) sets of “raw” echo images reconstructed using Tire-0, and its complex signal is modeled.
- Magnitude images present various blends of PD images, T1 and T2 * weights, while phase images contain background field and susceptibility effects mainly as a function of TE;
- Tire-2 images are calculated based on Tire-1 images Composite PDW/T 1 W/T 2 *W (cPDW/cT 1 W/cT 2 W) image, B 1 t image, T 1 image, enhanced T 1 W (aT 1 W) image, T 2 */R 2 * images, PD images, SWI images, QSM images, MRA images, etc.
- Tier-3 images are mainly calculated based on Tier-2 images, such as using advanced post-processing or virtual signal generation using the Bloch model.
- cPDW image, cT1W image and QSM image can be used to calculate the real SWI (tSWI) image, with the help of T 1 image, PD image and R 2 * (or T 2 *) image, can be used for inversion recovery (IR), Saturation Recovery (SR), Dual IR (DIR) or stabilized signal models to simulate images with virtual weighting effects, etc.
- IR inversion recovery
- SR Saturation Recovery
- DIR Dual IR
- WAMP provides multiple groups of qualitative images and multi-contrast parameter maps with high signal-to-noise ratio, quantitative accuracy and Acquisition/reconstruction efficiency.
- the WAMP signal acquisition design is also very flexible, and some additional comparison mechanisms can be added to meet wider application requirements.
- the point spread function PSF satisfies:
- m[x,y,z] is the image to be solved
- t is the time
- ⁇ is the gyromagnetic ratio
- k x , ky and k z are the k-space coordinates
- ⁇ is the integration time variable
- g y (t) and gz (t) are a pair of wave gradient fields out of phase by ⁇ /2 during readout. It can be known from the above formula that the effect of the wave-like gradient field can be expressed by Psf(t,y,z), which is a three-dimensional phase diagram that changes sinusoidally with time and changes linearly in the y and z directions respectively.
- the time t is linearly corresponding to the code k x of the readout direction of k space, and Psf(t, y, z) can also be written as Psf[k x , y, z] in discrete form.
- Perform Fourier transform of Psf[k x ,y,z] in the y and z directions that is, transform it into Psf[k x , ky ,k z ], which can describe the offset of the wave trajectory relative to the Cartesian trajectory .
- the inverse Fourier transform of Psf[k x ,y,z] in the readout direction is transformed into Psf[x,y,z], which can describe the diffusion effect of the wave gradient field in the readout direction.
- E is the encoding matrix
- E matrix needs to satisfy:
- Equation (6) shows that the coding model is an extended SENSE model, and the image of the echo signal can be reconstructed by using a solution method similar to the SENSE model.
- M0 is the baseline signal related to the proton density
- ⁇ represents the off-resonance effect (both global and local)
- W p and are the modulus weight and phase components of the sensitivity curve Cp of the pth coil channel, respectively, is a constant baseline phase.
- E 1 and E 2 represent and
- MDI multidimensional integration
- SNR signal-to-noise ratio
- a ratio or division operation for example, calculating R ⁇ B/A
- the corresponding value can be obtained as where L 1 , L 2 ... is the length of each feasible signal dimension, and a and b are single complex signal points from datasets A and B, as shown in equations (6) and (7).
- TE echo time
- TR repetition time
- C receiver coil channel
- Synthesized PDW and T 1 W images (cPDW and cT 1 W), for example, for cPDW, use the weighted average of all Acq 1 images, and for cT 1 W, use the weighted average of all Acq 2 images .
- B 1t mapped image AFI is applied on the image of Acq 2 's TR 1 and the first N 1 echo of TR 2 .
- the Acq 1 image is not used because ⁇ 1 is too small (set to PDW) for AFI to work properly.
- T 2 */R 2 * image apply the MDI method on the 2N 2 echo images of the two Acq modules.
- any mapping method of T 2 */R 2 * can be used.
- PD image Putting the B 1t , T 1 and T 2 * maps into formulas (6) and (7), a separate PD image can be extracted from each echo and then averaged. The averaged PD map can then be spatially normalized to reduce spatial variation related to coil sensitivity.
- Enhanced T 1 W (aT 1 W) map defined as the signal ratio between T 1 W and PDW signal, namely to eliminate non- T1 factors of pure T1 weighting.
- SWI image generated by using the multi-echo SWI image method based on 2N 2 sets of echo images of two Acq modules.
- any multi-echo SWI image method can be used.
- QSM image generated using the L 2 -norm optimization method, regularized with dynamic streak artifacts.
- any QSM method can be used.
- MRA image Optionally insert a frequency modulation module to create dark blood (with flow blanking) and bright blood (with flow compensation) images, and generate high-contrast MRA images by subtraction.
- Virtual image Using the respective Block signal models and the calculated T 1 /T 2 */PD/QSM image, an image with any virtual contrast can be generated, such as inversion recovery (IR), dual IR, PSIR, True SWI (tSWI), etc.
- IR inversion recovery
- PSIR dual IR
- tSWI True SWI
- Figure 4 is a WAMP imaging sequence scan to obtain a 4 times accelerated multi-contrast parametric image
- Figure 4(A) is the Tier-2 layer image, including qualitative images and parameter maps
- Figure 4(B) is the Tier-3 layer
- Example images including virtual IR and tSWI images.
- the tSWI image is calculated using susceptibility generated from the QSM map, and also utilizes cPDW+cT 1 W as its magnitude image.
- the present invention combines Wave-CAIPI (a 3D imaging method that utilizes multi-channel coils and k-space helical trajectory sampling to accelerate magnetic resonance imaging) technology and MULTIPLEX technology for three-dimensional multi-contrast magnetic resonance parameter imaging sequences .
- MULTIPLEX technology can use the signal destruction mechanism to collect incoherent steady-state (ISS) signals, and can obtain three-dimensional high-resolution (for example, voxel size ⁇ 1mm 3 ) imaging capabilities, improve data acquisition efficiency, easily build signal models, and can Compatible with various types of imaging sequences.
- the Wave-CAIPI technology can be used for high-acceleration three-dimensional imaging, and the loss of geometric factor (g-factor) and artifacts can be ignored at high acceleration.
- the method proposed by the invention is used for realizing three-dimensional multi-contrast magnetic resonance rapid parameter imaging with a single scan with high resolution, high signal-to-noise ratio, high accuracy, high efficiency and flexible acquisition.
- B 1t and T 1 images can be generated simultaneously through a sequence of scans, but also T 1 W images, proton density weighted (PDW) images, computationally enhanced T 1 W (aT 1 W ) images, susceptibility-weighted imaging (SWI) images, and optional qualitative MR angiography (MRA) images, as well as T2 * ( R2 *) images, PD (proton density) images, and quantitative susceptibility mapping (QSM) images etc.
- the present invention can be a system, method and/or computer program product.
- a computer program product may include a computer readable storage medium having computer readable program instructions thereon for causing a processor to implement various aspects of the present invention.
- a computer readable storage medium may be a tangible device that can retain and store instructions for use by an instruction execution device.
- a computer readable storage medium may be, for example, but is not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing.
- Computer-readable storage media include: portable computer diskettes, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), or flash memory), static random access memory (SRAM), compact disc read only memory (CD-ROM), digital versatile disc (DVD), memory stick, floppy disk, mechanically encoded device, such as a printer with instructions stored thereon A hole card or a raised structure in a groove, and any suitable combination of the above.
- RAM random access memory
- ROM read-only memory
- EPROM erasable programmable read-only memory
- flash memory static random access memory
- SRAM static random access memory
- CD-ROM compact disc read only memory
- DVD digital versatile disc
- memory stick floppy disk
- mechanically encoded device such as a printer with instructions stored thereon
- a hole card or a raised structure in a groove and any suitable combination of the above.
- computer-readable storage media are not to be construed as transient signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., pulses of light through fiber optic cables), or transmitted electrical signals.
- Computer-readable program instructions described herein may be downloaded from a computer-readable storage medium to a respective computing/processing device, or downloaded to an external computer or external storage device over a network, such as the Internet, a local area network, a wide area network, and/or a wireless network.
- the network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and/or edge servers.
- a network adapter card or a network interface in each computing/processing device receives computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in a computer-readable storage medium in each computing/processing device .
- Computer program instructions for carrying out operations of the present invention may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or Source or object code written in any combination, including object-oriented programming languages—such as C++, Python, JAVE, Smalltalk, etc., and conventional procedural programming languages—such as the “C” language, Fortran language, or similar Programming language.
- Computer readable program instructions may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer, or entirely on the remote computer or server implement.
- the remote computer can be connected to the user computer through any kind of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computer (such as via the Internet using an Internet service provider). connect).
- LAN local area network
- WAN wide area network
- an electronic circuit such as a programmable logic circuit, field programmable gate array (FPGA), or programmable logic array (PLA)
- FPGA field programmable gate array
- PDA programmable logic array
- These computer-readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine such that when executed by the processor of the computer or other programmable data processing apparatus , producing an apparatus for realizing the functions/actions specified in one or more blocks in the flowchart and/or block diagram.
- These computer-readable program instructions can also be stored in a computer-readable storage medium, and these instructions cause computers, programmable data processing devices and/or other devices to work in a specific way, so that the computer-readable medium storing instructions includes An article of manufacture comprising instructions for implementing various aspects of the functions/acts specified in one or more blocks in flowcharts and/or block diagrams.
- each block in a flowchart or block diagram may represent a module, a portion of a program segment, or an instruction that includes one or more Executable instructions.
- the functions noted in the block may occur out of the order noted in the figures. For example, two blocks in succession may, in fact, be executed substantially concurrently, or they may sometimes be executed in the reverse order, depending upon the functionality involved.
- each block of the block diagrams and/or flowchart illustrations, and combinations of blocks in the block diagrams and/or flowchart illustrations can be implemented by a dedicated hardware-based system that performs the specified function or action , or may be implemented by a combination of dedicated hardware and computer instructions. It is well known to those skilled in the art that implementation by means of hardware, implementation by means of software, and implementation by a combination of software and hardware are all equivalent.
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Abstract
A magnetic resonance multi contrast-ratio parameter imaging method based on a wave-type gradient. The method comprises: collecting a magnetic resonance imaging sequence, wherein the sequence includes two times of repetition (TR1, TR2) and two flip angles (α1, α2), and each time of repetition (TR1, TR2) includes a plurality of echoes; when a readout gradient is applied to the magnetic resonance imaging sequence, applying a cosine wave gradient (CO) sequence in the direction of a selected layer by using a magnetic resonance gradient field coil, and applying a sine wave gradient (SI) sequence in the direction of a phase, or applying the cosine wave gradient (CO) sequence in the direction of the phase, and applying the sine wave gradient (SI) sequence in the direction of the selected layer; and applying a wave-type gradient sequence to a gradient recalled echo imaging (GRE) sequence, performing under-sampling on a signal to obtain a multi-layer image, and then obtaining, on the basis of the multi-layer image, a parameter image having a plurality of contrast ratios. By means of the method, a parameter image having a plurality of contrast ratios is obtained by means of a single scan, thereby significantly shortening the scan time, and improving the definition of the generated image.
Description
本发明涉及医学图像分析技术领域,更具体地,涉及一种基于波浪式梯度的磁共振多对比度参数成像方法。The invention relates to the technical field of medical image analysis, and more particularly, to a wave-like gradient-based magnetic resonance multi-contrast parameter imaging method.
磁共振成像技术(Magnetic Resonance Imaging,MRI)是通过对静磁场中的目标施加特定频率的射频脉冲,使该目标中的氢质子受到激励而发生磁共振现象。在停止施加射频脉冲后,目标中的质子在弛豫过程中产生磁共振MR信号,通过对该MR信号的接收、空间编码和图像重建等处理过程,即可获得可用的MR信号。由于磁共振过程中,每一个信号都含有全层的信息,因此需要对磁共振信号进行空间定位编码,即频率编码和相位编码。具体地,因为接收线圈采集到的MR信号实际是带有空间编码信息的无线电波,属于模拟信号,所以需要经过模数转换变成数字信息,再将数字信息填充到k空间,最后得到相应的数字点阵。其中,k空间与磁共振信号的空间定位息息相关,该k空间也叫傅里叶空间,是带有空间定位编码信息的MR信号原始数字信息的填充空间。每一幅MR图像都有其相应的k空间数据点阵,通过对k空间的数据进行傅里叶转换,就能对原始数字数据中的空间定位编码信息进行解码,分解出不同频率、相位和幅度的MR信号,不同的频率和相位代表不同的空间位置,而幅度则代表MR信号强度。将不同频率、相位及信号强度的MR数字信号分配到相应的像素中,就得到MR图像数据,也即重建出了MR图像。傅里叶变换就是将k空间的原始数据点阵转变成MR图像点阵的过程。Magnetic resonance imaging (Magnetic Resonance Imaging, MRI) is to apply a specific frequency radio frequency pulse to the target in the static magnetic field, so that the hydrogen protons in the target are excited and magnetic resonance phenomenon occurs. After the application of radio frequency pulses is stopped, the protons in the target generate magnetic resonance MR signals during the relaxation process, and the usable MR signals can be obtained through the processing of the MR signal reception, spatial encoding and image reconstruction. Since each signal contains full-layer information during the magnetic resonance process, it is necessary to perform spatial positioning encoding on the magnetic resonance signal, namely frequency encoding and phase encoding. Specifically, because the MR signal collected by the receiving coil is actually a radio wave with space-encoded information, which is an analog signal, it needs to be transformed into digital information through analog-to-digital conversion, and then the digital information is filled into the k-space, and finally the corresponding Digital dot matrix. Among them, k-space is closely related to the spatial positioning of magnetic resonance signals. This k-space is also called Fourier space, which is the filling space of the original digital information of MR signals with spatial positioning coding information. Each MR image has its corresponding k-space data lattice. By Fourier transforming the k-space data, the spatial positioning coding information in the original digital data can be decoded, and different frequencies, phases and For the MR signal of the amplitude, different frequencies and phases represent different spatial positions, and the amplitude represents the MR signal intensity. The MR digital signals of different frequencies, phases and signal strengths are allocated to the corresponding pixels to obtain MR image data, that is, to reconstruct the MR image. Fourier transform is the process of transforming the original data lattice of k-space into MR image lattice.
近年来,多对比度参数磁共振成像技术得到了广泛的开发和探索。原则上来说,几乎任何信号准备和采集策略,如纵向恢复,螺旋轨迹成像,回波平面成像(EPI),稳态自由进动成像(SSFP),梯度重聚回波成像(GRE) 等都可以潜在地用作开发多参数成像方法的基础。具体而言,GRE采集使用横向信号破坏机制来收集非相干稳态(ISS)信号可能具有一定的优势,例如可以获得三维高分辨率成像能力,高数据采集效率,容易构建信号模型,以及可以兼容各种成像序列和加速技术。In recent years, multi-contrast parametric MRI techniques have been extensively developed and explored. In principle, almost any signal preparation and acquisition strategy, such as longitudinal recovery, helical trajectory imaging, echo planar imaging (EPI), steady state free precession imaging (SSFP), gradient refocusing echo imaging (GRE), etc. Potentially used as a basis for developing multiparametric imaging methods. Specifically, GRE acquisition using a transverse signal destruction mechanism to collect incoherent steady-state (ISS) signals may have certain advantages, such as three-dimensional high-resolution imaging capabilities, high data acquisition efficiency, easy construction of signal models, and compatibility with Various imaging sequences and acceleration techniques.
另一方面,磁共振成像的成像速度慢,过长的扫描时间在引起病患不适的同时,容易在图像中引入运动伪影,从而影响图像质量。磁共振并行成像方法是一类加速MRI扫描速度的方法,例如同时获取空间谐波技术(SMASH,simultaneous acquisition of spatial harmonics)、灵敏度编码技术(SENSE,sensitivity encoding)和整体自动校准部分并行采集技术(GRAPPA,generalized autocalibrating partially parallel acquisitions)等。这类方法通过减少采集的数据量,并利用多通道线圈所包含的冗余信息对欠采样数据进行重建,从而到达快速扫描的目的。在现有技术中,并行成像已经通过多个接收线圈被用于加速各种磁共振成像序列,并存在一些改进方法来实现更高的加速倍数,例如,同时多层(SMS)成像,受控混叠加速技术(CAIPIRINHA),聚束相位编码技术(BPE),体积并行成像中的受控混叠技术(2D CAIPIRINHA),体积并行成像中的波浪式梯度下受控混叠加速技术(Wave-CAIPI)等。这些策略已成功应用于回波平面成像,高分辨率的功能和弥散加权成像,动脉自旋标记成像(ASL),动态磁化率对比成像等应用。On the other hand, the imaging speed of magnetic resonance imaging is slow, and the long scanning time will cause discomfort to the patient, and at the same time, it is easy to introduce motion artifacts in the image, thereby affecting the image quality. Magnetic resonance parallel imaging method is a kind of method to accelerate the scanning speed of MRI, such as simultaneous acquisition of spatial harmonics technology (SMASH, simultaneous acquisition of spatial harmonics), sensitivity encoding technology (SENSE, sensitivity encoding) and overall automatic calibration partial parallel acquisition technology ( GRAPPA, generalized autocalibrating partially parallel acquisitions), etc. This type of method achieves the purpose of fast scanning by reducing the amount of collected data and using the redundant information contained in the multi-channel coil to reconstruct the under-sampled data. In the prior art, parallel imaging has been used to speed up various MRI sequences with multiple receive coils, and some improvements exist to achieve higher acceleration factors, for example, simultaneous multislice (SMS) imaging, controlled Hybrid acceleration technology (CAIPIRINHA), beam spotting phase encoding technology (BPE), controlled aliasing technology in volume parallel imaging (2D CAIPIRINHA), controlled mixing acceleration technology in wave-like gradient in volume parallel imaging (Wave- CAIPI) and so on. These strategies have been successfully applied in echo-planar imaging, high-resolution functional and diffusion-weighted imaging, arterial spin labeling imaging (ASL), dynamic susceptibility contrast imaging and other applications.
然而,在目前的临床应用中,为了获得具有不同对比度的多个磁共振图像,需要应用对应于多个对比度的多个脉冲序列,因此现有技术中的多对比度的磁共振参数成像技术总扫描时间长,扫描中病患者不适和运动的风险高,并且需要多种扫描序列多次扫描,数据采集效率低,构建信号模型复杂,在高加速时几何因子(g-factor)和伪影偏大。However, in current clinical applications, in order to obtain multiple magnetic resonance images with different contrasts, multiple pulse sequences corresponding to multiple contrasts need to be applied, so the multi-contrast magnetic resonance parametric imaging technology in the prior art total scan Long time, high risk of patient discomfort and movement during scanning, multiple scans in multiple scan sequences are required, data acquisition efficiency is low, signal model building is complicated, and the geometric factor (g-factor) and artifacts are too large at high acceleration .
发明内容Contents of the invention
本发明的目的是克服上述现有技术的缺陷,提供一种基于波浪式梯度的磁共振多对比度参数成像方法,以减少临床应用中多对比度的磁共振参数成像的总扫描时间,改善扫描过程中患者的不适和运动的风险。The purpose of the present invention is to overcome the above-mentioned defective of prior art, provide a kind of magnetic resonance multi-contrast parameter imaging method based on wave type gradient, to reduce the total scan time of the magnetic resonance parameter imaging of multi-contrast in clinical application, improve scanning process. Patient discomfort and risk of exercise.
本发明的技术方案是:提供一种基于波浪式梯度的磁共振多对比度参数成像方法,包括以下步骤:采集磁共振成像序列,该序列包含双重复时间、双翻转角,且每一重复时间包含多个回波;针对所述磁共振成像序列施加读出梯度时,利用磁共振梯度场线圈在选层方向施加余弦波浪梯度序列,并在相位方向施加正弦波浪梯度序列;或者在相位方向施加余弦波浪梯度序列,在选层方向施加正弦波浪梯度序列;将所述波浪式梯度序列应用于梯度重聚回波成像序列,并对信号进行欠采样,获得多层图像,进而基于所述多层图像,获得多种对比度的参数图像。The technical solution of the present invention is to provide a wave-like gradient-based magnetic resonance multi-contrast parameter imaging method, comprising the following steps: acquiring a magnetic resonance imaging sequence, the sequence includes double repetition time, double flip angle, and each repetition time includes A plurality of echoes; when applying a readout gradient to the magnetic resonance imaging sequence, the magnetic resonance gradient field coil is used to apply a cosine wave gradient sequence in the layer selection direction, and a sine wave gradient sequence is applied in the phase direction; or a cosine wave is applied in the phase direction A wave gradient sequence, applying a sinusoidal wave gradient sequence in the layer selection direction; applying the wave gradient sequence to a gradient refocusing echo imaging sequence, and under-sampling the signal to obtain a multi-layer image, and then based on the multi-layer image , to obtain parametric images of various contrasts.
与现有技术相比,本发明的优点在于,可以实现高倍加速扫描的同时,降低几何因子g-factor,并且避免了伪影的产生;相对于现有Wave-CAIPI技术,本发明提出的成像方法,解决了Wave-CAIPI技术一次扫描只能产生单一对比度图像的问题,可以实现单次扫描就获得多种对比度参数图像,并且显著缩短了对比度参数成像的扫描时间。Compared with the prior art, the present invention has the advantage that it can realize high-magnification accelerated scanning while reducing the geometric factor g-factor and avoiding the generation of artifacts; compared with the existing Wave-CAIPI technology, the imaging proposed by the present invention The method solves the problem that one scan of Wave-CAIPI technology can only produce a single contrast image, and can obtain multiple contrast parameter images in a single scan, and significantly shortens the scanning time of contrast parameter imaging.
通过以下参照附图对本发明的示例性实施例的详细描述,本发明的其它特征及其优点将会变得清楚。Other features of the present invention and advantages thereof will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings.
被结合在说明书中并构成说明书的一部分的附图示出了本发明的实施例,并且连同其说明一起用于解释本发明的原理。The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.
图1是根据本发明一个实施例的磁共振成像序列采集方案的示意图;FIG. 1 is a schematic diagram of an MRI sequence acquisition scheme according to an embodiment of the present invention;
图2是根据本发明一个实施例的磁共振成像序列中的读出梯度RO、余弦波浪梯度CO、正弦波浪梯度SI以及在k空间采样模板的示意图;Fig. 2 is a schematic diagram of readout gradient RO, cosine wave gradient CO, sine wave gradient SI and sampling template in k-space in a magnetic resonance imaging sequence according to an embodiment of the present invention;
图3是根据本发明一个实施例的磁共振成像序列的图像处理流水线示意图;Fig. 3 is a schematic diagram of an image processing pipeline of a magnetic resonance imaging sequence according to an embodiment of the present invention;
图4是根据本发明一个实施例的一次磁共振成像序列扫描获得4倍加速多对比度的参数图像示意图。Fig. 4 is a schematic diagram of a parametric image of a 4-fold accelerated multi-contrast obtained by one magnetic resonance imaging sequence scan according to an embodiment of the present invention.
现在将参照附图来详细描述本发明的各种示例性实施例。应注意到: 除非另外具体说明,否则在这些实施例中阐述的部件和步骤的相对布置、数字表达式和数值不限制本发明的范围。Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangements of components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.
以下对至少一个示例性实施例的描述实际上仅仅是说明性的,决不作为对本发明及其应用或使用的任何限制。The following description of at least one exemplary embodiment is merely illustrative in nature and in no way taken as limiting the invention, its application or uses.
对于相关领域普通技术人员已知的技术、方法和设备可能不作详细讨论,但在适当情况下,所述技术、方法和设备应当被视为说明书的一部分。Techniques, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such techniques, methods and devices should be considered part of the description.
在这里示出和讨论的所有例子中,任何具体值应被解释为仅仅是示例性的,而不是作为限制。因此,示例性实施例的其它例子可以具有不同的值。In all examples shown and discussed herein, any specific values should be construed as exemplary only, and not as limitations. Therefore, other instances of the exemplary embodiment may have different values.
应注意到:相似的标号和字母在下面的附图中表示类似项,因此,一旦某一项在一个附图中被定义,则在随后的附图中不需要对其进行进一步讨论。It should be noted that like numerals and letters denote like items in the following figures, therefore, once an item is defined in one figure, it does not require further discussion in subsequent figures.
本发明提供一种基于波浪式梯度和梯度重聚回波成像(GRE)序列的磁共振快速成像方法,序列采用了波浪式梯度、双TR(重复时间)、双翻转角(FA)和多回波设计,可用于三维高分辨率的多对比度的磁共振快速参数成像,也被称为WAMP成像(Wave-CAIPI MULTIPLEX,简称WAMP)。The invention provides a magnetic resonance fast imaging method based on wave-like gradient and gradient refocusing echo imaging (GRE) sequence, the sequence adopts wave-like gradient, double TR (repetition time), double flip angle (FA) and multiple The wave design can be used for three-dimensional high-resolution multi-contrast MRI rapid parametric imaging, also known as WAMP imaging (Wave-CAIPI MULTIPLEX, WAMP for short).
本发明基于Wave-CAIPI技术(“Wave-CAIPI for highly accelerated 3D imaging”,Magn Reson Med,2015年6月;73(6):2152-62;Bilgic B,et al.)和MULTIPLEX(“MULTI-parametric MR imaging with fLEXible design(MULTIPLEX)”,Magn Reson Med,2021年8月31.doi:10.1002/mrm.28999;Ye Y,et al.)技术实现多对比度参数的超快速成像方法,可以实现一种单次扫描获得的多对比度参数图像的解决方案。简言之,本发明的技术方案包括:The present invention is based on Wave-CAIPI technology (“Wave-CAIPI for highly accelerated 3D imaging”, Magn Reson Med, June 2015; 73(6):2152-62; Bilgic B, et al.) and MULTIPLEX (“MULTI- parametric MR imaging with fLEXible design (MULTIPLEX)", Magn Reson Med, 2021 August 31. doi:10.1002/mrm.28999; Ye Y, et al.) technology to achieve ultra-fast imaging method with multiple contrast parameters, which can realize a A solution for multi-contrast parametric images acquired in a single scan. In short, the technical solution of the present invention includes:
1)、在三维磁共振成像序列采集信号的同时(施加读出梯度的同时),利用磁共振梯度场线圈在选层方向(或相位方向)施加余弦波浪梯度序列。与此同时,在相位方向(或选层方向)施加正弦波浪梯度序列;1) While acquiring signals in a three-dimensional magnetic resonance imaging sequence (while applying a readout gradient), the magnetic resonance gradient field coil is used to apply a cosine wave gradient sequence in the layer selection direction (or phase direction). At the same time, apply a sinusoidal wave gradient sequence in the phase direction (or layer selection direction);
2)、将上述波浪式梯度序列应用于GRE序列,并且对信号进行欠采样加速。其中,沿着相位编码方向在k空间采样的采样模板采用规则欠采样;2) Apply the above-mentioned wave-like gradient sequence to the GRE sequence, and perform under-sampling acceleration on the signal. Among them, the sampling template sampled in k-space along the phase encoding direction adopts regular undersampling;
3)、将步骤(1)和(2)所述技术方法应用于三维WAMP序列,并通过构建信号模型和图像处理技术,获得多种对比度的参数图像,其中包括B
1t图像、T
1图像、T
2图像、T
1加权(T
1W)图像、增强T
1加权T
1W(aT
1W)图像、T
2加权(T
2W)图像、增强T
2加权T
2W(aT
2W)图像、T2*(T2*)图像、质子密度(PD)图像、质子密度加权(PDW)图像、磁化率加权成像(SWI)图像和定量磁化率映射(QSM)图像,以及磁共振血管造影(MRA)等图像。
3), applying the technical method described in step (1) and (2) to the three-dimensional WAMP sequence, and by constructing a signal model and image processing technology, obtaining parameter images of multiple contrasts, including B 1t image, T 1 image, T 2 image, T 1 weighted (T 1 W) image, enhanced T 1 weighted T 1 W (aT 1 W) image, T 2 weighted (T 2 W) image, enhanced T 2 weighted T 2 W (aT 2 W) images, T2* (T2*) images, proton density (PD) images, proton density-weighted (PDW) images, susceptibility-weighted imaging (SWI) images, and quantitative susceptibility mapping (QSM) images, and magnetic resonance angiography (MRA ) and other images.
1)关于磁共振成像序列设计1) Regarding MRI sequence design
参见图1所示,WAMP成像序列具有双重复时间(TR)、双翻转角(FA)(包括α
1和α
2)和多回波设计。双TR(包括TR
1和TR
2)特征源自用于B
1t映射的实际翻转角成像(actual flip angle imaging,AFI)技术。Acq
1(对应图1的上半部分采集过程模块,或称第一采集模块)和Acq
2(对应图1的下半部分采集过程模块,或称第二采集模块)各包含一个与实际翻转角度(AFI)技术类似的双TR单元。在每个TR(即TR
1和TR
2)内,获取一定数量(即N
1和N
2)的梯度回波。此外,可以灵活地插入流动调制(FM)块。每个采集模块(Acq)使用不同的翻转角(如α
1/α
2),每个TR模块有不同数量的回波和/或不同的FM功能(包括开/关状态)。其中,在每一个回波处的频率编码方向都有对应的读出梯度RO(RO和Acq同时触发),在选层编码方向(或相位方向)方向施加余弦波浪梯度CO,在相位编码方向(或选层编码方向)施加正弦波浪梯度SI。在一个实施例中,在WAMP成像序列中RO、CO和SI的梯度脉冲,和在k空间采样的模板采用隔行隔列规则进行欠采样,如图2所示,其中图2(a)是梯度波形,图2(b)是采样示例,图2(c)是k空间轨迹。为简单起见,下文的讨论假设α
1<α
2,N
1<N
2和TR
1<TR
2。
Referring to Fig. 1, the WAMP imaging sequence has double repetition time (TR), double flip angle (FA) (including α 1 and α 2 ) and multi-echo design. The dual TR (comprising TR 1 and TR 2 ) features are derived from the actual flip angle imaging (AFI) technique for B 1 t mapping. Acq 1 (corresponding to the upper part of the acquisition process module in Figure 1, or called the first acquisition module) and Acq 2 (corresponding to the lower part of the acquisition process module in Figure 1, or called the second acquisition module) each contain a (AFI) Technology similar dual TR unit. Within each TR (ie TR 1 and TR 2 ), a certain number (ie N 1 and N 2 ) of gradient echoes are acquired. Additionally, Flow Modulation (FM) blocks can be inserted flexibly. Each acquisition module (Acq) uses a different flip angle (eg α 1 /α 2 ), each TR module has a different number of echoes and/or a different FM function (including on/off status). Among them, there is a corresponding readout gradient RO in the frequency encoding direction at each echo (RO and Acq are triggered simultaneously), a cosine wave gradient CO is applied in the layer selection encoding direction (or phase direction), and a cosine wave gradient CO is applied in the phase encoding direction ( Or select layer encoding direction) apply sinusoidal wave gradient SI. In one embodiment, the gradient pulses of RO, CO, and SI in the WAMP imaging sequence, and the template sampled in k-space are under-sampled using the rule of every row and every column, as shown in Figure 2, where Figure 2(a) is the gradient Waveforms, Figure 2(b) is a sampling example, and Figure 2(c) is a k-space trajectory. For simplicity, the following discussion assumes α 1 <α 2 , N 1 <N 2 and TR 1 <TR 2 .
仍结合图1所示,一次WAMP序列的扫描可以生成2(N
1+N
2)回波图像集。此外,可以在每个激励脉冲后选择性地插入流动调制(FM)块。经过WAMP序列扫描的数据图像的处理流水线如图3所示。为简单起见,以WAMP数据图像分为四层(Tier-0,Tier-1,Tier-2和Tier-3)为例,具体取决于它们在处理管道中的计算顺序和关系,并采用多维集成(MDI)的概念用于高信噪比(SNR)、高保真度和高效的复杂图像处理。第Tire-0层图像是 从各个k空间采集数据通过Wave-CAIPI信号,利用SENSE模型的线性方程求解,获得2(N
1+N
2)组“原始”回波图像;第Tire-1层图像是利用Tire-0重建的2(N
1+N
2)组“原始”回波图像,对其复信号进行建模。幅度图像呈现PD图像、T
1和T
2*权重的各种混合图像,而相位图像包含主要作为TE函数的背景场和磁化率效应;第Tire-2层图像是基于第Tire-1层图像计算出复合PDW/T
1W/T
2*W(cPDW/cT
1W/cT
2W)图像,B
1t图像,T
1图像,增强T
1W(aT
1W)图像,T
2*/R
2*图像,PD图像,SWI图像,QSM图像,MRA图像等;第Tier-3层图像主要基于第Tire-2层图像计算,例如使用高级后处理或使用Bloch模型的虚拟信号生成。例如,cPDW图像、cT1W图像和QSM图像可用于计算真实SWI(tSWI)图像,借助T
1图像、PD图像和R
2*(或T
2*)图像,可以通过用于反转恢复(IR)、饱和恢复(SR)、双IR(DIR)或稳定的信号模型来模拟具有虚拟加权效果的图像等。凭借基于双TR、双FA和多回波GRE的设计,以及结合MDI和其他先进算法的专用图像处理程序,WAMP提供多组定性图像和多对比度参数图,具有高信噪比、定量准确度和采集/重建效率。此外,WAMP信号采集设计也很灵活,可以额外加入某些对比机制,以满足更广泛的应用需求。
Still combined with what is shown in FIG. 1 , a WAMP sequence scan can generate 2 (N 1 +N 2 ) echo image sets. Additionally, a Flow Modulation (FM) block can be optionally inserted after each excitation pulse. The processing pipeline of the data image scanned by WAMP sequence is shown in Figure 3. For simplicity, take WAMP data images as an example divided into four layers (Tier-0, Tier-1, Tier-2, and Tier-3), depending on their calculation order and relationship in the processing pipeline, and adopt multi-dimensional integration (MDI) concept for high signal-to-noise ratio (SNR), high fidelity and efficient complex image processing. The Tire-0 layer image is collected data from each k-space through the Wave-CAIPI signal, using the linear equation of the SENSE model to solve, and obtains 2 (N 1 +N 2 ) groups of "original" echo images; the Tire-1 layer image is the 2(N 1 +N 2 ) sets of “raw” echo images reconstructed using Tire-0, and its complex signal is modeled. Magnitude images present various blends of PD images, T1 and T2 * weights, while phase images contain background field and susceptibility effects mainly as a function of TE; Tire-2 images are calculated based on Tire-1 images Composite PDW/T 1 W/T 2 *W (cPDW/cT 1 W/cT 2 W) image, B 1 t image, T 1 image, enhanced T 1 W (aT 1 W) image, T 2 */R 2 * images, PD images, SWI images, QSM images, MRA images, etc.; Tier-3 images are mainly calculated based on Tier-2 images, such as using advanced post-processing or virtual signal generation using the Bloch model. For example, cPDW image, cT1W image and QSM image can be used to calculate the real SWI (tSWI) image, with the help of T 1 image, PD image and R 2 * (or T 2 *) image, can be used for inversion recovery (IR), Saturation Recovery (SR), Dual IR (DIR) or stabilized signal models to simulate images with virtual weighting effects, etc. With the design based on double TR, double FA and multi-echo GRE, and a dedicated image processing program combined with MDI and other advanced algorithms, WAMP provides multiple groups of qualitative images and multi-contrast parameter maps with high signal-to-noise ratio, quantitative accuracy and Acquisition/reconstruction efficiency. In addition, the WAMP signal acquisition design is also very flexible, and some additional comparison mechanisms can be added to meet wider application requirements.
2)、图像重建模型2), image reconstruction model
结合图3所示,以下详细阐述WAMP的原理,其k空间的信号模型表示为:Combined with Figure 3, the principle of WAMP is described in detail below, and the signal model of its k-space is expressed as:
其中点扩散函数PSF满足:The point spread function PSF satisfies:
其中,m[x,y,z]为待求解图像,t表示时间,γ表示旋磁比,k
x、k
y和k
z分别表示k空间坐标,τ表示积分时间变量,g
y(t)和g
z(t)是在读出期间一对相位相差π/2的波浪梯度场。由以上式子可知,波浪式梯度场作用效果可以用Psf(t,y,z)表示,它是一个随时间正弦周期变化,且分别在y和z方向线性变化的三维相位图。其中时间t与k空间读出方向的编码k
x是一一线性对应的,Psf(t,y,z)也可以写作离散形式的Psf[k
x,y,z]。将Psf[k
x,y,z]在y和z方向上做傅里叶变换,即变换成Psf[k
x,k
y,k
z],它可以描述波浪轨迹相对笛 卡尔轨迹的偏移量。将Psf[k
x,y,z]在读出方向上做反傅里叶变换,即变换成Psf[x,y,z],它可以描述波浪梯度场在读出方向的扩散效应。
Among them, m[x,y,z] is the image to be solved, t is the time, γ is the gyromagnetic ratio, k x , ky and k z are the k-space coordinates, τ is the integration time variable, g y (t) and gz (t) are a pair of wave gradient fields out of phase by π/2 during readout. It can be known from the above formula that the effect of the wave-like gradient field can be expressed by Psf(t,y,z), which is a three-dimensional phase diagram that changes sinusoidally with time and changes linearly in the y and z directions respectively. The time t is linearly corresponding to the code k x of the readout direction of k space, and Psf(t, y, z) can also be written as Psf[k x , y, z] in discrete form. Perform Fourier transform of Psf[k x ,y,z] in the y and z directions, that is, transform it into Psf[k x , ky ,k z ], which can describe the offset of the wave trajectory relative to the Cartesian trajectory . The inverse Fourier transform of Psf[k x ,y,z] in the readout direction is transformed into Psf[x,y,z], which can describe the diffusion effect of the wave gradient field in the readout direction.
基于公式(1),拓展到多通道线圈并行采集,并考虑相位编码方向的k空间欠采样,并对公式两边做反傅里叶变换,写成矩阵表达的离散形式的信号编码公式:Based on formula (1), it is extended to parallel acquisition of multi-channel coils, and the k-space undersampling in the phase encoding direction is considered, and the inverse Fourier transform is performed on both sides of the formula, and the signal encoding formula expressed in a matrix is written in discrete form:
wave[x,y,z]=Em[x,y,z](3)wave[x,y,z]=Em[x,y,z](3)
其中E是编码矩阵,且E矩阵需要满足:Where E is the encoding matrix, and the E matrix needs to satisfy:
其中S表示线圈敏感度编码,F
x表示在读出方向的傅里叶变换,M表示在相位编码方向由隔行隔列规则欠采样模式(如图2所示)导致的偏移混叠。实际上,公式(3)和(4)可以等价写成:
where S represents the coil sensitivity encoding, F x represents the Fourier transform in the readout direction, and M represents the offset aliasing caused by the regular undersampling mode of every row and every column (as shown in Figure 2) in the phase coding direction. In fact, formulas (3) and (4) can be equivalently written as:
以上的公式(5)也相当于一种卷积操作:The above formula (5) is also equivalent to a convolution operation:
其中Psf[x,y,z]是Psf[k
x,y,z]在读出方向的反傅里叶变换,
是在读出方向的卷积操作。公式(6)说明,编码模型是一个扩展的SENSE模型,可以利用类似SENSE模型求解方法重建回波信号的图像。
where Psf[x,y,z] is the inverse Fourier transform of Psf[k x ,y,z] in the readout direction, is the convolution operation in the readout direction. Equation (6) shows that the coding model is an extended SENSE model, and the image of the echo signal can be reconstructed by using a solution method similar to the SENSE model.
3)、图像信号处理过程3), image signal processing process
在图像重建之后,对于多回波信号的图像,将根据其磁共振成像的物理效应进行图像处理和生成。假设在翻转角α
i(i∈[1,2])),回波时间TE
j(j∈[1,N
1])和TE(k∈[1,N
2])下,TR
1(即S
1)和TR
2(即S
2)的图像信号分别为:
After image reconstruction, for the image of multi-echo signal, image processing and generation will be carried out according to the physical effect of its magnetic resonance imaging. Assume that under flip angle α i (i∈[1,2])), echo time TE j (j∈[1, N 1 ]) and TE(k∈[1, N 2 ]), TR 1 (ie The image signals of S 1 ) and TR 2 (ie S 2 ) are respectively:
其中M
0是与质子密度相关的基线信号,Δω代表非共振效应(包括全局和局部),W
p和
分别是第p
th个线圈通道的灵敏度曲线C
p的模数权重和相位分量,
是恒定的基线相位。E
1和E
2分别代表
和
where M0 is the baseline signal related to the proton density, Δω represents the off-resonance effect (both global and local), W p and are the modulus weight and phase components of the sensitivity curve Cp of the pth coil channel, respectively, is a constant baseline phase. E 1 and E 2 represent and
在图像的计算过程中,多维集成(MDI)的概念已被提出用于高信噪比(SNR)、高保真度和高效的复杂图像处理。MDI的工作原理是:当定义一 个比率或除法运算时,例如,计算R≡B/A,可以得到相应的数值为
其中L
1,L
2...是每个可行信号维度的长度,a和b是来自数据集A和B的单个复信号点,如等式(6)和(7)所示。利用MDI概念于WAMP信号维度,其中包括FA(α),回波时间(time of echo,简称为TE)、重复时间(time of repetition,简称为TR)和接收器线圈通道(coil,简称为C)。在2(N
1+N
2)组直接采集后重建的图像上,通过相应的图像处理方法可以得到以下结果:
In the computational process of images, the concept of multidimensional integration (MDI) has been proposed for high signal-to-noise ratio (SNR), high fidelity, and efficient complex image processing. The working principle of MDI is: when defining a ratio or division operation, for example, calculating R≡B/A, the corresponding value can be obtained as where L 1 , L 2 ... is the length of each feasible signal dimension, and a and b are single complex signal points from datasets A and B, as shown in equations (6) and (7). Using the MDI concept in the WAMP signal dimension, including FA(α), echo time (time of echo, referred to as TE), repetition time (time of repetition, referred to as TR) and receiver coil channel (coil, referred to as C ). On 2(N 1 +N 2 ) groups of directly collected and reconstructed images, the following results can be obtained through corresponding image processing methods:
1)、合成的PDW和T
1W图像(cPDW和cT
1W),例如,对cPDW而言,采用所有Acq
1图像的加权平均,对cT
1W而言,采用所有Acq
2图像的加权平均。
1) Synthesized PDW and T 1 W images (cPDW and cT 1 W), for example, for cPDW, use the weighted average of all Acq 1 images, and for cT 1 W, use the weighted average of all Acq 2 images .
2)、B
1t映射图像:在Acq
2的TR
1和TR
2的第一个N
1回波的图像上应用AFI。Acq
1图像没有被使用,因为α
1太小(设置为PDW),AFI不能正常工作。
2), B 1t mapped image: AFI is applied on the image of Acq 2 's TR 1 and the first N 1 echo of TR 2 . The Acq 1 image is not used because α 1 is too small (set to PDW) for AFI to work properly.
3)、T
1的映射图像:假设TR
1和TR
2都<<T
1,令k=TR
1/T
1和nk=TR
2/T
1,k的解析可以从公式(6)和(7)中提取,形式为ak
2+bk+c=0,因此T
1=TR
1/k。有了第2步的B
1t图,可以得到一个修正的T
1图。
3), the mapping image of T 1 : assuming that both TR 1 and TR 2 << T 1 , let k=TR 1 /T 1 and nk=TR 2 /T 1 , the analysis of k can be obtained from formulas (6) and (7 ), the form is ak 2 +bk+c=0, so T 1 =TR 1 /k. With the B 1t map in step 2, a modified T 1 map can be obtained.
4)、T
2*/R
2*图像:在两个Acq模块的2N
2组回声图像上应用MDI方法。原则上,可以使用任何T
2*/R
2*的映射方法。
4), T 2 */R 2 * image: apply the MDI method on the 2N 2 echo images of the two Acq modules. In principle, any mapping method of T 2 */R 2 * can be used.
5)、PD图像:将B
1t、T
1和T
2*图放入公式(6)和(7)中,可以从每个回波中提取单独的PD图像,然后进行平均。然后可以对平均的PD图进行空间归一化,以减少与线圈敏感性有关的空间变化。
5) PD image: Putting the B 1t , T 1 and T 2 * maps into formulas (6) and (7), a separate PD image can be extracted from each echo and then averaged. The averaged PD map can then be spatially normalized to reduce spatial variation related to coil sensitivity.
6)、增强的T
1W(aT
1W)图:定义为T
1W和PDW信号之间的信号比,即
以消除纯T
1加权的非T
1因素。
6), Enhanced T 1 W (aT 1 W) map: defined as the signal ratio between T 1 W and PDW signal, namely to eliminate non- T1 factors of pure T1 weighting.
7)、SWI图像:使用基于两个Acq模块的2N
2套回声图像的多回声SWI图像方法生成。原则上,可以使用任何多回波SWI图像方法。
7) SWI image: generated by using the multi-echo SWI image method based on 2N 2 sets of echo images of two Acq modules. In principle, any multi-echo SWI image method can be used.
8)、QSM图像:使用L
2-norm优化方法生成的,带有动态条纹伪影的正则化。原则上,可以使用任何QSM方法。
8), QSM image: generated using the L 2 -norm optimization method, regularized with dynamic streak artifacts. In principle, any QSM method can be used.
9)、MRA图像:可选择插入调频模块,以创建暗血(含流量消隐)和亮血(含流量补偿)图像,并通过减法生成高对比度的MRA图像。9), MRA image: Optionally insert a frequency modulation module to create dark blood (with flow blanking) and bright blood (with flow compensation) images, and generate high-contrast MRA images by subtraction.
10)、虚拟图像:使用各自的Block信号模型和计算出的T
1/T
2*/PD/QSM图像,可以生成具有任意虚拟对比度的图像,如反转恢复(IR)、双IR、PSIR、真SWI(tSWI)等。
10) Virtual image: Using the respective Block signal models and the calculated T 1 /T 2 */PD/QSM image, an image with any virtual contrast can be generated, such as inversion recovery (IR), dual IR, PSIR, True SWI (tSWI), etc.
为进一步验证本发明的效果,进行了实验。经验证,本发明可以实现单次扫描快速成像,获得4~9倍加速下的三维高分辨率多对比度的磁共振参数成像,且体素分辨率可以达到≤1mm
3,扫描时间可以达到1.1~2.5分钟。图4是一次WAMP成像序列扫描获得4倍加速多对比度的参数图像,其中图4(A)是第Tier-2层图像,包括定性图像和参数图,图4(B)是第Tier-3层图像示例,包括虚拟IR和tSWI图像。其中tSWI图像是使用从QSM图生成的磁化率来计算,并且也利用cPDW+cT
1W作为其幅度图像。
In order to further verify the effect of the present invention, experiments were carried out. It has been verified that the present invention can realize rapid single-scan imaging, obtain three-dimensional high-resolution multi-contrast magnetic resonance parameter imaging under 4-9 times acceleration, and the voxel resolution can reach ≤1mm 3 , and the scan time can reach 1.1- 2.5 minutes. Figure 4 is a WAMP imaging sequence scan to obtain a 4 times accelerated multi-contrast parametric image, where Figure 4(A) is the Tier-2 layer image, including qualitative images and parameter maps, and Figure 4(B) is the Tier-3 layer Example images, including virtual IR and tSWI images. where the tSWI image is calculated using susceptibility generated from the QSM map, and also utilizes cPDW+cT 1 W as its magnitude image.
综上所述,本发明将Wave-CAIPI(一种利用多通道线圈和k空间螺旋轨迹采样来加速磁共振成像的3D成像方法)技术和MULTIPLEX技术结合用于三维多对比度的磁共振参数成像序列。MULTIPLEX技术可以使用信号破坏机制来收集非相干稳态(ISS)信号,并可以获得三维高分辨率(例如,体素尺寸<1mm
3)成像能力,提高数据采集效率,容易构建信号模型,以及可以兼容各种类型的成像序列。而Wave-CAIPI技术可以用于高加速的三维成像,并且在高加速时候可以忽略不计几何因子(g-factor)和伪影的损失。本发明所提出的方法用于具有高分辨率、高信噪比、高准确性、高效率和采集灵活的单次扫描实现三维多对比度的磁共振快速参数成像。在本发明提供的技术方案中,通过一次序列的扫描不仅可以同时生成B
1t和T
1图像,还可以生成T
1W图像、质子密度加权(PDW)图像、计算增强T
1W(aT
1W)图像、磁化率加权成像(SWI)图像和可选的定性图像MR血管造影(MRA)图像,以及T
2*(R
2*)图像、PD(质子密度)图像和定量磁化率映射(QSM)图像等。
In summary, the present invention combines Wave-CAIPI (a 3D imaging method that utilizes multi-channel coils and k-space helical trajectory sampling to accelerate magnetic resonance imaging) technology and MULTIPLEX technology for three-dimensional multi-contrast magnetic resonance parameter imaging sequences . MULTIPLEX technology can use the signal destruction mechanism to collect incoherent steady-state (ISS) signals, and can obtain three-dimensional high-resolution (for example, voxel size <1mm 3 ) imaging capabilities, improve data acquisition efficiency, easily build signal models, and can Compatible with various types of imaging sequences. The Wave-CAIPI technology can be used for high-acceleration three-dimensional imaging, and the loss of geometric factor (g-factor) and artifacts can be ignored at high acceleration. The method proposed by the invention is used for realizing three-dimensional multi-contrast magnetic resonance rapid parameter imaging with a single scan with high resolution, high signal-to-noise ratio, high accuracy, high efficiency and flexible acquisition. In the technical solution provided by the present invention, not only B 1t and T 1 images can be generated simultaneously through a sequence of scans, but also T 1 W images, proton density weighted (PDW) images, computationally enhanced T 1 W (aT 1 W ) images, susceptibility-weighted imaging (SWI) images, and optional qualitative MR angiography (MRA) images, as well as T2 * ( R2 *) images, PD (proton density) images, and quantitative susceptibility mapping (QSM) images etc.
本发明可以是系统、方法和/或计算机程序产品。计算机程序产品可以包括计算机可读存储介质,其上载有用于使处理器实现本发明的各个方面的计算机可读程序指令。The present invention can be a system, method and/or computer program product. A computer program product may include a computer readable storage medium having computer readable program instructions thereon for causing a processor to implement various aspects of the present invention.
计算机可读存储介质可以是可以保持和存储由指令执行设备使用的指令的有形设备。计算机可读存储介质例如可以是但不限于电存储设备、 磁存储设备、光存储设备、电磁存储设备、半导体存储设备或者上述的任意合适的组合。计算机可读存储介质的更具体的例子(非穷举的列表)包括:便携式计算机盘、硬盘、随机存取存储器(RAM)、只读存储器(ROM)、可擦式可编程只读存储器(EPROM或闪存)、静态随机存取存储器(SRAM)、便携式压缩盘只读存储器(CD-ROM)、数字多功能盘(DVD)、记忆棒、软盘、机械编码设备、例如其上存储有指令的打孔卡或凹槽内凸起结构、以及上述的任意合适的组合。这里所使用的计算机可读存储介质不被解释为瞬时信号本身,诸如无线电波或者其他自由传播的电磁波、通过波导或其他传输媒介传播的电磁波(例如,通过光纤电缆的光脉冲)、或者通过电线传输的电信号。A computer readable storage medium may be a tangible device that can retain and store instructions for use by an instruction execution device. A computer readable storage medium may be, for example, but is not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer diskettes, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), or flash memory), static random access memory (SRAM), compact disc read only memory (CD-ROM), digital versatile disc (DVD), memory stick, floppy disk, mechanically encoded device, such as a printer with instructions stored thereon A hole card or a raised structure in a groove, and any suitable combination of the above. As used herein, computer-readable storage media are not to be construed as transient signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., pulses of light through fiber optic cables), or transmitted electrical signals.
这里所描述的计算机可读程序指令可以从计算机可读存储介质下载到各个计算/处理设备,或者通过网络、例如因特网、局域网、广域网和/或无线网下载到外部计算机或外部存储设备。网络可以包括铜传输电缆、光纤传输、无线传输、路由器、防火墙、交换机、网关计算机和/或边缘服务器。每个计算/处理设备中的网络适配卡或者网络接口从网络接收计算机可读程序指令,并转发该计算机可读程序指令,以供存储在各个计算/处理设备中的计算机可读存储介质中。Computer-readable program instructions described herein may be downloaded from a computer-readable storage medium to a respective computing/processing device, or downloaded to an external computer or external storage device over a network, such as the Internet, a local area network, a wide area network, and/or a wireless network. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and/or edge servers. A network adapter card or a network interface in each computing/processing device receives computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in a computer-readable storage medium in each computing/processing device .
用于执行本发明操作的计算机程序指令可以是汇编指令、指令集架构(ISA)指令、机器指令、机器相关指令、微代码、固件指令、状态设置数据、或者以一种或多种编程语言的任意组合编写的源代码或目标代码,所述编程语言包括面向对象的编程语言—诸如C++、Python、JAVE、Smalltalk等,以及常规的过程式编程语言—诸如“C”语言、Fortran语言或类似的编程语言。计算机可读程序指令可以完全地在用户计算机上执行、部分地在用户计算机上执行、作为一个独立的软件包执行、部分在用户计算机上部分在远程计算机上执行、或者完全在远程计算机或服务器上执行。在涉及远程计算机的情形中,远程计算机可以通过任意种类的网络—包括局域网(LAN)或广域网(WAN)—连接到用户计算机,或者,可以连接到外部计算机(例如利用因特网服务提供商来通过因特网连接)。在一些实施例中,通过利用计算机可读程序指令的状态信息来个性化定制电子电路,例如可编 程逻辑电路、现场可编程门阵列(FPGA)或可编程逻辑阵列(PLA),该电子电路可以执行计算机可读程序指令,从而实现本发明的各个方面。Computer program instructions for carrying out operations of the present invention may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or Source or object code written in any combination, including object-oriented programming languages—such as C++, Python, JAVE, Smalltalk, etc., and conventional procedural programming languages—such as the “C” language, Fortran language, or similar Programming language. Computer readable program instructions may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer, or entirely on the remote computer or server implement. In cases involving a remote computer, the remote computer can be connected to the user computer through any kind of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computer (such as via the Internet using an Internet service provider). connect). In some embodiments, an electronic circuit, such as a programmable logic circuit, field programmable gate array (FPGA), or programmable logic array (PLA), can be customized by utilizing state information of computer-readable program instructions, which can Various aspects of the invention are implemented by executing computer readable program instructions.
这里参照根据本发明实施例的方法、装置(系统)和计算机程序产品的流程图和/或框图描述了本发明的各个方面。应当理解,流程图和/或框图的每个方框以及流程图和/或框图中各方框的组合,都可以由计算机可读程序指令实现。Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It should be understood that each block of the flowcharts and/or block diagrams, and combinations of blocks in the flowcharts and/or block diagrams, can be implemented by computer-readable program instructions.
这些计算机可读程序指令可以提供给通用计算机、专用计算机或其它可编程数据处理装置的处理器,从而生产出一种机器,使得这些指令在通过计算机或其它可编程数据处理装置的处理器执行时,产生了实现流程图和/或框图中的一个或多个方框中规定的功能/动作的装置。也可以把这些计算机可读程序指令存储在计算机可读存储介质中,这些指令使得计算机、可编程数据处理装置和/或其他设备以特定方式工作,从而,存储有指令的计算机可读介质则包括一个制造品,其包括实现流程图和/或框图中的一个或多个方框中规定的功能/动作的各个方面的指令。These computer-readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine such that when executed by the processor of the computer or other programmable data processing apparatus , producing an apparatus for realizing the functions/actions specified in one or more blocks in the flowchart and/or block diagram. These computer-readable program instructions can also be stored in a computer-readable storage medium, and these instructions cause computers, programmable data processing devices and/or other devices to work in a specific way, so that the computer-readable medium storing instructions includes An article of manufacture comprising instructions for implementing various aspects of the functions/acts specified in one or more blocks in flowcharts and/or block diagrams.
也可以把计算机可读程序指令加载到计算机、其它可编程数据处理装置、或其它设备上,使得在计算机、其它可编程数据处理装置或其它设备上执行一系列操作步骤,以产生计算机实现的过程,从而使得在计算机、其它可编程数据处理装置、或其它设备上执行的指令实现流程图和/或框图中的一个或多个方框中规定的功能/动作。It is also possible to load computer-readable program instructions into a computer, other programmable data processing device, or other equipment, so that a series of operational steps are performed on the computer, other programmable data processing device, or other equipment to produce a computer-implemented process , so that instructions executed on computers, other programmable data processing devices, or other devices implement the functions/actions specified in one or more blocks in the flowcharts and/or block diagrams.
附图中的流程图和框图显示了根据本发明的多个实施例的系统、方法和计算机程序产品的可能实现的体系架构、功能和操作。在这点上,流程图或框图中的每个方框可以代表一个模块、程序段或指令的一部分,所述模块、程序段或指令的一部分包含一个或多个用于实现规定的逻辑功能的可执行指令。在有些作为替换的实现中,方框中所标注的功能也可以以不同于附图中所标注的顺序发生。例如,两个连续的方框实际上可以基本并行地执行,它们有时也可以按相反的顺序执行,这依所涉及的功能而定。也要注意的是,框图和/或流程图中的每个方框、以及框图和/或流程图中的方框的组合,可以用执行规定的功能或动作的专用的基于硬件的系统来实现,或者可以用专用硬件与计算机指令的组合来实现。对于本领域技术人 员来说公知的是,通过硬件方式实现、通过软件方式实现以及通过软件和硬件结合的方式实现都是等价的。The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, a portion of a program segment, or an instruction that includes one or more Executable instructions. In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks in succession may, in fact, be executed substantially concurrently, or they may sometimes be executed in the reverse order, depending upon the functionality involved. It should also be noted that each block of the block diagrams and/or flowchart illustrations, and combinations of blocks in the block diagrams and/or flowchart illustrations, can be implemented by a dedicated hardware-based system that performs the specified function or action , or may be implemented by a combination of dedicated hardware and computer instructions. It is well known to those skilled in the art that implementation by means of hardware, implementation by means of software, and implementation by a combination of software and hardware are all equivalent.
以上已经描述了本发明的各实施例,上述说明是示例性的,并非穷尽性的,并且也不限于所披露的各实施例。在不偏离所说明的各实施例的范围和精神的情况下,对于本技术领域的普通技术人员来说许多修改和变更都是显而易见的。本文中所用术语的选择,旨在最好地解释各实施例的原理、实际应用或对市场中的技术改进,或者使本技术领域的其它普通技术人员能理解本文披露的各实施例。本发明的范围由所附权利要求来限定。Having described various embodiments of the present invention, the foregoing description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and alterations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principle of each embodiment, practical application or technical improvement in the market, or to enable other ordinary skilled in the art to understand each embodiment disclosed herein. The scope of the invention is defined by the appended claims.
Claims (10)
- 一种基于波浪式梯度的磁共振多对比度参数成像方法,包括以下步骤:A magnetic resonance multi-contrast parameter imaging method based on wave-like gradients, comprising the following steps:步骤S1:采集磁共振成像序列,该序列包含双重复时间、双翻转角,且每一重复时间包含多个回波;Step S1: acquiring a magnetic resonance imaging sequence, the sequence includes double repetition times, double flip angles, and each repetition time includes multiple echoes;步骤S2:针对所述磁共振成像序列施加读出梯度时,利用磁共振梯度场线圈在选层方向施加余弦波浪梯度序列,并在相位方向施加正弦波浪梯度序列;或者在相位方向施加余弦波浪梯度序列,在选层方向施加正弦波浪梯度序列;Step S2: When applying a readout gradient to the magnetic resonance imaging sequence, use the magnetic resonance gradient field coil to apply a cosine wave gradient sequence in the layer selection direction, and apply a sine wave gradient sequence in the phase direction; or apply a cosine wave gradient in the phase direction Sequence, applying a sine wave gradient sequence in the layer selection direction;步骤S3:将所述波浪式梯度序列应用于梯度重聚回波成像序列,并对信号进行欠采样,获得多层图像,进而基于所述多层图像获得多种对比度的参数图像。Step S3: applying the wave-like gradient sequence to a gradient refocusing echo imaging sequence, and under-sampling the signal to obtain a multi-layer image, and then obtain parametric images of various contrasts based on the multi-layer image.
- 根据权利要求1所述的方法,其特征在于,所述磁共振成像序列具有第一重复时间TR 1和第二重复时间TR 2,第一翻转角和第二翻转角,其中第一重复时间对应N1个梯度回波,第二重复时间对应N2个梯度回波,且第一重复时间与第二重复时间具有不同的流动调制块。 The method according to claim 1, wherein the magnetic resonance imaging sequence has a first repetition time TR 1 and a second repetition time TR 2 , a first flip angle and a second flip angle, wherein the first repetition time corresponds to N1 gradient echoes, the second repetition time corresponds to N2 gradient echoes, and the first repetition time and the second repetition time have different flow modulation blocks.
- 根据权利要求1所述的方法,对于所述磁共振成像序列,其读出梯度RO、余弦波浪梯度CO、正弦波浪梯度SI和在k空间采样的模板采用隔行隔列规则欠采样。The method according to claim 1, for the magnetic resonance imaging sequence, the readout gradient RO, the cosine wave gradient CO, the sine wave gradient SI and the templates sampled in k-space are under-sampled with the rule of every row and every column.
- 根据权利要求1所述的方法,其特征在于,所述多种对比度的参数图像包括B 1t图像、T 1图像、T 2图像、T 1加权图像、增强T 1加权图像、T 2加权图像、增强T 2加权T 2W图像、T2*图像、质子密度图像、质子密度加权图像、磁化率加权成像图像、定量磁化率映射图像和磁共振血管造影图像中的至少5种。 The method according to claim 1, wherein the parametric images of the multiple contrasts include B 1t images, T 1 images, T 2 images, T 1 weighted images, enhanced T 1 weighted images, T 2 weighted images, Enhance at least 5 of T2 - weighted T2W images, T2* images, proton density images, proton density-weighted images, susceptibility-weighted imaging images, quantitative susceptibility mapping images, and magnetic resonance angiography images.
- 根据权利要求2所述的方法,其特征在于,对于所述磁共振成像序列,其k空间的信号模型表示为:The method according to claim 2, wherein, for the magnetic resonance imaging sequence, the signal model of its k-space is expressed as:其中点扩散函数PSF满足:The point spread function PSF satisfies:其中,m[x,y,z]为待求解图像,t表示时间,γ表示旋磁比,k x、k y和k z分别表示k空间坐标,τ表示积分时间变量,g y(t)和g z(t)是在读出期间一对相位相差π/2的波浪梯度场,Psf(t,y,z)是一个随时间正弦周期变化,且分别在y和z方向线性变化的三维相位图,时间t与k空间读出方向的编码k x一一线性对应,Psf(t,y,z)的离散形式表示为Psf[k x,y,z],将Psf[k x,y,z]在y和z方向上做傅里叶变换,变换成Psf[k x,k y,k z]用于描述波浪轨迹相对笛卡尔轨迹的偏移量,将Psf[k x,y,z]在读出方向上做反傅里叶变换,变换成Psf[x,y,z],用于描述波浪梯度场在读出方向的扩散效应。 Among them, m[x,y,z] is the image to be solved, t is the time, γ is the gyromagnetic ratio, k x , ky and k z are the k-space coordinates, τ is the integration time variable, g y (t) and g z (t) are a pair of wave gradient fields with a phase difference of π/2 during readout, and Psf(t,y,z) is a three-dimensional In the phase diagram, the time t is linearly corresponding to the code k x of the k-space readout direction, the discrete form of Psf(t,y,z) is expressed as Psf[k x ,y,z], and Psf[k x ,y , z] do Fourier transform in the y and z directions, and transform it into Psf[k x , k y , k z ] to describe the offset of the wave trajectory relative to the Cartesian trajectory. Psf[k x ,y, z] is inversely Fourier transformed in the readout direction, transformed into Psf[x, y, z], which is used to describe the diffusion effect of the wave gradient field in the readout direction.
- 根据权利要求2所述的方法,其特征在于,对应于所述磁共振成像序列,图像的生成过程表示为:The method according to claim 2, wherein, corresponding to the magnetic resonance imaging sequence, the image generation process is expressed as:假设在翻转角α i,回波时间TE j和回波时间TE k下,对应第一重复时间TR1和对应第二重复时间TR2的图像信号分别为: Assuming that at flip angle α i , echo time TE j and echo time TE k , the image signals corresponding to the first repetition time TR1 and corresponding to the second repetition time TR2 are respectively:其中i∈[1,2],j∈[1,N 1],k∈[1,N 2],M 0是与质子密度相关的基线信号,Δω代表非共振效应,W p和 是第p th个线圈通道的灵敏度曲线C p的模数权重和相位分量, 是恒定的基线相位,E 1和E 2分别代表 和 T 1表示纵向驰豫时间。 where i ∈ [1, 2], j ∈ [1, N 1 ], k ∈ [1, N 2 ], M 0 is the baseline signal related to proton density, Δω represents the non-resonance effect, W p and are the modulus weights and phase components of the sensitivity curve Cp of the pth coil channel, is the constant baseline phase, and E1 and E2 represent and T 1 represents the longitudinal relaxation time.
- 根据权利要求2所述的方法,其特征在于,所述多层图像包含四层,第一层图像是从各个k空间采集数据通过Wave-CAIPI信号利用SENSE模型的线性方程求解获得的2(N 1+N 2)组原始回波图像;第二层图像是利用第一组图像对其复信号进行建模获得,其幅度图像呈现PD图像、T 1和T 2*权重的各种混合图像,而相位图像包含背景场和磁化率效应;第三层图像是基于第二层图像计算出的复合PDW/T 1W/T 2*W图像,B 1t图像,T 1图像,增强T 1W图像,T 2*/R 2*图像,PD图像,SWI图像,QSM图像,MRA图像;第四层图像是基于第三层图像计算的cPDW图像、cT1W图像和QSM图像,并用于计算真实SWI图像。 The method according to claim 2, wherein the multi-layer image comprises four layers, and the first layer image is 2(N obtained by using the linear equation solution of the SENSE model through the Wave-CAIPI signal from each k-space acquisition data 1 +N 2 ) group of original echo images; the second layer image is obtained by using the first group of images to model its complex signal, and its magnitude image presents various mixed images of PD image, T 1 and T 2 * weights , while the phase image contains background field and magnetic susceptibility effects; the third layer image is a composite PDW/T 1 W/T 2 *W image calculated based on the second layer image, B 1 t image, T 1 image, enhanced T 1 W image, T2 */ R2 * image, PD image, SWI image, QSM image, MRA image; the fourth layer image is the cPDW image, cT1W image and QSM image calculated based on the third layer image, and used to calculate the real SWI image.
- 根据权利要求2所述的方法,其特征在于,对应于所述磁共振成像序列,第一采集模块使用第一翻转角在第一重复时间TR 1和第二重复时间TR 2内获取N 1+N 2个梯度回波,第二采集模块利用第二翻转角在第一重复时间TR 1和第二重复时间TR 2内获取N 1+N 2个梯度回波。 The method according to claim 2, characterized in that, corresponding to the magnetic resonance imaging sequence, the first acquisition module uses the first flip angle to acquire N 1 + N 2 gradient echoes, the second acquisition module acquires N 1 +N 2 gradient echoes within the first repetition time TR 1 and the second repetition time TR 2 by using the second flip angle.
- 一种计算机可读存储介质,其上存储有计算机程序,其中,该程序被处理器执行时实现根据权利要求1至8中任一项所述方法的步骤。A computer-readable storage medium, on which a computer program is stored, wherein, when the program is executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.
- 一种计算机设备,包括存储器和处理器,在所述存储器上存储有能够在处理器上运行的计算机程序,其特征在于,所述处理器执行所述程序时实现权利要求1至8中任一项所述的方法的步骤。A computer device comprising a memory and a processor, wherein a computer program capable of running on the processor is stored on the memory, wherein any one of claims 1 to 8 is implemented when the processor executes the program The steps of the method described in the item.
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