Magnetic resonance multi-contrast fast imaging method and device based on spiral trajectory acquisition

Abstract

This application provides a method and apparatus for rapid multi-contrast magnetic resonance imaging based on helical trajectory acquisition. The method includes: constructing a modular multi-contrast imaging pulse sequence composed of multiple preparation modules, each preparation module being used to generate different magnetic resonance signals; generating magnetic resonance signals according to the modular multi-contrast imaging pulse sequence, and acquiring the magnetic resonance signals using a helical trajectory to obtain acquired magnetic resonance signals; and performing imaging reconstruction based on the acquired magnetic resonance signals to obtain magnetic resonance images with different contrasts. This method improves the generation efficiency of magnetic resonance signals by generating magnetic resonance signals with different contrasts through a modular multi-contrast imaging pulse sequence. Since the helical acquisition trajectory has high encoding efficiency, using a helical trajectory acquisition can effectively improve the acquisition efficiency of magnetic resonance signals, thus increasing the imaging speed of multi-contrast magnetic resonance images.

Description

Technical Field

[0001] This application relates to the field of magnetic resonance imaging technology, and in particular to a method and apparatus for rapid multi-contrast magnetic resonance imaging based on spiral trajectory acquisition. Background Technology

[0002] Magnetic resonance imaging (MRI) is a non-invasive medical imaging technique that produces no ionizing radiation and offers rich tissue contrast. MRI can obtain structural and functional information about living tissues and plays a crucial role in clinical medical diagnosis and neuroscience research.

[0003] The signals acquired by magnetic resonance imaging (MRI) are related to the magnetic resonance parameters and physiological function parameters of the tissue. Typically, there are differences in one or more magnetic resonance parameters and physiological function parameters between different tissues, and between normal and diseased tissues. Choosing appropriate imaging sequences and parameters can increase the signal differences between different tissues, resulting in increased contrast on the MRI image.

[0004] Single-contrast MRI images can only reflect a single aspect of the structure or property of the imaged tissue, insufficient to provide comprehensive information for distinguishing different tissues. In clinical MRI scans, multiple-contrast MRI images are typically acquired, and the nature of the tissue is determined by the signal characteristics of the same tissue at different contrast levels. Acquiring multi-contrast MRI images is usually achieved through multiple acquisitions, each yielding an image with a different contrast level. Conventional MRI uses a Cartesian acquisition sequence, which is inefficient; acquiring multiple-contrast MRI images is time-consuming, resulting in lower imaging efficiency for multi-contrast MRI.

[0005] Therefore, achieving efficient acquisition of magnetic resonance signals and improving the imaging efficiency of multi-contrast magnetic resonance images are urgent technical problems to be solved. Summary of the Invention

[0006] In view of the above problems, this application provides a method and apparatus for rapid multi-contrast magnetic resonance imaging based on helical trajectory acquisition, so as to solve the problems of low acquisition efficiency and low resolution of multi-contrast images in magnetic resonance imaging.

[0007] A first aspect of this application discloses a rapid multi-contrast magnetic resonance imaging method based on helical trajectory acquisition, the method comprising:

[0008] A modular multi-contrast imaging pulse sequence consisting of multiple preparation modules was constructed, with each preparation module used to generate a different magnetic resonance signal;

[0009] A magnetic resonance signal is generated based on the modular multi-contrast imaging pulse sequence, and the magnetic resonance signal is acquired using a spiral trajectory to obtain the acquired magnetic resonance signal.

[0010] Based on the acquired magnetic resonance signals, imaging reconstruction is performed to obtain magnetic resonance images with different contrasts.

[0011] Optionally, a modular multi-contrast imaging pulse sequence consisting of multiple preparation modules is constructed, including:

[0012] Based on the imaging characteristics of magnetic resonance images, excitation, refocusing, and flipping radio frequency pulses are used, and the repetition time and echo time are set by modifying the corresponding gradient coding to obtain preparation modules with different contrasts.

[0013] Based on the magnetic resonance images of different contrasts to be acquired, the corresponding preparation modules are selected to form a modular multi-contrast imaging pulse sequence.

[0014] Optionally, the magnetic resonance signal is acquired using a helical trajectory to obtain the acquired magnetic resonance signal, including:

[0015] Based on the accelerated acquisition strategy, the magnetic resonance signal is acquired by using a multiple excitation method to obtain the acquired magnetic resonance signal.

[0016] The aforementioned mining acceleration strategies include: a radial mining acceleration strategy and a spiral trajectory rearrangement strategy.

[0017] Optionally, based on a radial downsampling strategy, the magnetic resonance signal is acquired using a multiple excitation method, including:

[0018] By modifying the gradient waveform of the spiral acquisition trajectory, a spiral acquisition trajectory with increased radial spacing in k-space is obtained;

[0019] Based on the spiral acquisition trajectory with increasing radial spacing within the k-space, the magnetic resonance signal is acquired multiple times until a complete magnetic resonance signal distributed within the k-space is obtained.

[0020] Optionally, the magnetic resonance signal is acquired multiple times according to the spiral acquisition trajectory with increasing radial spacing within the k-space, including:

[0021] The magnetic resonance signal is acquired sequentially from the center of k-space to the edge of k-space, following a spiral acquisition trajectory with increasing radial spacing within k-space.

[0022] Optionally, based on a spiral trajectory rearrangement strategy, the magnetic resonance signal is acquired using a multiple excitation method, including:

[0023] Increase the rotation angle between multiple excitation spiral acquisition trajectories, the magnitude of which is negatively correlated with the number of excitations of the spiral acquisition trajectory required to obtain the complete magnetic resonance signal distributed in k-space;

[0024] The spiral acquisition trajectory is excited multiple times according to the rotation angle, and the magnetic resonance signal is acquired according to the spiral acquisition trajectory to obtain the complete magnetic resonance signal distributed in the k-space.

[0025] Optionally, imaging reconstruction is performed based on the acquired magnetic resonance signals to obtain magnetic resonance images with different contrasts, including:

[0026] Based on the acquired magnetic resonance signals, the common information and coil sensitivity distribution information of magnetic resonance images with different contrasts are determined.

[0027] Imaging reconstruction is performed based on the common information of the magnetic resonance images with different contrasts and the coil sensitivity distribution information to obtain magnetic resonance images with different contrasts.

[0028] A second aspect of this application discloses a magnetic resonance multi-contrast rapid imaging device based on helical trajectory acquisition, the device comprising:

[0029] The building module is used to construct a modular multi-contrast imaging pulse sequence consisting of multiple preparation modules, each of which is used to generate a different magnetic resonance signal.

[0030] The acquisition module generates a magnetic resonance signal based on the modular multi-contrast imaging pulse sequence, and acquires the magnetic resonance signal using a spiral trajectory to obtain the acquired magnetic resonance signal.

[0031] The reconstruction module performs imaging reconstruction based on the acquired magnetic resonance signals to obtain magnetic resonance images with different contrasts.

[0032] A third aspect of this application discloses an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the magnetic resonance multi-contrast rapid imaging method based on helical trajectory acquisition described in the first aspect of this application.

[0033] A fourth aspect of this application discloses a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the magnetic resonance multi-contrast rapid imaging method based on helical trajectory acquisition described in the first aspect of this application.

[0034] The embodiments of this application have the following advantages:

[0035] In this embodiment, leveraging the high spatial coding efficiency of helical trajectory acquisition, a rapid multi-contrast magnetic resonance imaging method based on helical trajectory acquisition is proposed. A modular multi-contrast imaging pulse sequence is constructed, consisting of multiple preparation modules, each generating a different magnetic resonance signal. The magnetic resonance signal is generated according to the modular multi-contrast imaging pulse sequence and acquired using a helical trajectory. Finally, imaging reconstruction is performed based on the acquired magnetic resonance signal to obtain magnetic resonance images with different contrasts. Because the helical acquisition trajectory has high spatial coding efficiency, using it to acquire magnetic resonance signals improves the acquisition efficiency, thus increasing the imaging speed of multi-contrast magnetic resonance images.

[0036] Thus, the magnetic resonance multi-contrast rapid imaging method based on helical trajectory acquisition provided in this application fully utilizes the high signal sampling efficiency of helical acquisition, enabling efficient and high-resolution imaging (e.g., on a high-field magnetic resonance system, an intra-slice resolution of 1.0 mm can be achieved in approximately 2 minutes). 2 It can acquire multi-contrast images (e.g., T1W FLAIR, T2W, PDW, T2*W, T2W FLAIR, DWI); and based on the acquired multi-contrast images, it can calculate quantitative parameter maps such as apparent diffusion coefficient (ADC) to provide auxiliary diagnostic information. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a flowchart of the steps of a magnetic resonance multi-contrast fast imaging method based on spiral trajectory acquisition provided in an embodiment of this application;

[0039] Figure 2 This is a schematic diagram of a multi-contrast imaging pulse sequence provided in an embodiment of this application;

[0040] Figure 3 This is a schematic diagram of a spiral acquisition radial reduction strategy provided in an embodiment of this application;

[0041] Figure 4 This is a schematic diagram of a spiral acquisition trajectory rearrangement strategy provided in an embodiment of this application;

[0042] Figure 5This is a schematic diagram of magnetic resonance imaging results with different contrast provided in an embodiment of this application;

[0043] Figure 6 This is a schematic diagram of another magnetic resonance imaging result with different contrast provided in an embodiment of this application;

[0044] Figure 7 This is a schematic diagram of the structure of a magnetic resonance multi-contrast rapid imaging device based on spiral trajectory acquisition provided in an embodiment of this application;

[0045] Figure 8 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0046] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0047] In magnetic resonance imaging (MRI), multi-contrast MRI images are used to reflect the structure and properties of the same tissue. Commonly used contrast ratios include T1-weighted imaging, T2-weighted imaging, proton density (PD)-weighted imaging, and T2*-weighted imaging. For different imaging organs and different imaging needs, other contrast ratios are often required. For example, head imaging also requires diffusion-weighted imaging and fluid attenuated inversion recovery (FLAIR).

[0048] In related technologies, magnetic resonance imaging (MRI) uses a Cartesian acquisition sequence, which has low acquisition efficiency, and acquiring multiple contrast MRI images takes a considerable amount of time. However, rapid multi-contrast MRI is highly necessary in clinical practice. For example, patients with acute ischemic stroke, traumatic brain injury, hypermobility, children, and patients with insufficient motor control all require rapid MRI examinations. Rapid imaging techniques can reduce motion-related artifacts, reduce the need for sedation, and increase scan volume. Furthermore, in low-field MRI, such as 0.5T, 0.55T, and 0.6T (less than 1.0T), the signal-to-noise ratio of the MRI images decreases due to the reduced magnetic field. To ensure sufficiently fast imaging speeds, high acquisition efficiency becomes even more crucial.

[0049] In some magnetic resonance imaging (MRI) methods, single-shot echo planar imaging (EPI) acquisition sequences are used to acquire MRI images with various contrasts (e.g., T1W, T2W, etc.) within approximately one minute. However, this method suffers from low spatial resolution and image geometric distortion. Other MRI methods use multi-shot EPI acquisition sequences for correlated, rapid multi-contrast imaging, but this method also suffers from low spatial resolution and image geometric distortion. Compared to EPI, spiral acquisition has an isotropic point spread function and is more efficient in terms of spatial coding.

[0050] In summary, magnetic resonance imaging (MRI) generally requires the acquisition of multi-contrast images, but existing MRI techniques suffer from low sampling efficiency and low image resolution. Therefore, this application's embodiments leverage the high-efficiency spatial coding capability of helical trajectory acquisition. Furthermore, considering that in low-field MRI systems, magnetic field inhomogeneity weakens and the magnetic dielectric constant decreases, helical trajectory acquisition imaging, which is easily affected by magnetic field inhomogeneity, does not exhibit severe artifacts as in high-field or ultra-high-field systems. Thus, multi-contrast MRI using helical trajectory acquisition is suitable for application in low-field MRI systems. This application's embodiments provide a rapid multi-contrast MRI imaging method based on helical trajectory acquisition, fully utilizing the high signal acquisition efficiency of helical trajectory acquisition to achieve efficient and high-resolution acquisition of multi-contrast images.

[0051] Based on the spiral trajectory acquisition-based rapid multi-contrast magnetic resonance imaging method provided in this application embodiment, on the one hand, on a high-field magnetic resonance system, it can acquire six contrast magnetic resonance images and calculate the relevant parameter maps in about 2 minutes, providing a new option for rapid clinical head magnetic resonance imaging; on the other hand, it can be applied to low-field magnetic resonance systems (≤1.0T), making full use of the high signal sampling efficiency of spiral acquisition to provide a solution for multi-contrast imaging.

[0052] The following detailed description of the magnetic resonance multi-contrast rapid imaging method based on spiral trajectory acquisition of this application, with reference to the accompanying drawings, will be provided.

[0053] This application provides a method for rapid multi-contrast magnetic resonance imaging based on helical trajectory acquisition, referring to... Figure 1 As shown, Figure 1 This is a flowchart illustrating the steps of a rapid multi-contrast magnetic resonance imaging method based on helical trajectory acquisition, as provided in an embodiment of this application. Figure 1 As shown, the method may include steps S110 to S130:

[0054] Step S110: Construct a modular multi-contrast imaging pulse sequence consisting of multiple preparation modules, each preparation module being used to generate a different magnetic resonance signal.

[0055] In this embodiment, each preparation module corresponds to a type of imaging pulse sequence, and different contrasts are achieved by using different preparation modules. For example, in Figure 2 The section marked with a dashed line represents the inversion recovery module, which is used in preparing T1W-FLAIR and T2W-FLAIR images for both contrast ratios. By constructing a modular multi-contrast imaging pulse sequence, magnetic resonance signals with different contrast ratios can be generated rapidly, thus improving the imaging speed of multi-contrast magnetic resonance images to some extent.

[0056] In one optional embodiment, a modular multi-contrast imaging pulse sequence consisting of multiple preparation modules is constructed, including: setting the repetition time and echo time for different contrasts by using excitation, convergence, and flip radio frequency pulses and modifying the corresponding gradient coding according to the imaging characteristics of the magnetic resonance image; and selecting the corresponding preparation modules to form a modular multi-contrast imaging pulse sequence according to the magnetic resonance images of different contrasts to be acquired.

[0057] Here, repetition time (TR) and echo time (TE) are used. Different preparation modules are implemented by setting different imaging pulse sequence parameters. For example, FLAIR contrast magnetic resonance images can be obtained based on the inversion recovery sequence; diffusion-weighted images can be obtained by applying two identical diffusion-coded gradients (Stejskal-Tanner method) on the left and right sides of the 180° refocusing radio frequency pulse; and gradient echo sequences can be used to obtain... Weighted magnetic resonance images. Based on the different contrast magnetic resonance images to be acquired, the corresponding preparation module is selected to obtain the corresponding magnetic resonance signal.

[0058] The following sections describe the T1W-FLAIR imaging pulse sequences, T2W-FLAIR imaging pulse sequences, PD-weighted imaging pulse sequences, T2-weighted imaging pulse sequences, and diffusion-weighted imaging pulse sequences. The parameters of six different contrast imaging pulse sequences for weighted imaging pulse sequences are explained.

[0059] (1) For T1W-FLAIR imaging pulse sequences, inversion recovery pulses were used to enhance T1-weighted contrast to suppress cerebrospinal fluid signals, and the inversion recovery time (TI) was determined by considering the use of short TE and short TR parameters. The inversion recovery time (TI) varies at different field strengths; for example, the inversion recovery time (TI) at a 3T field strength is approximately 950 ms.

[0060] (2) For T2W-FALIR imaging pulse sequences, longer TE and TR parameters are used to ensure T2-weighted contrast in the magnetic resonance images, and the inversion recovery time (TI) is determined taking into account the suppression of cerebrospinal fluid signals. For example, the inversion recovery time (TI) at a 3T field strength is 2200 ms.

[0061] (3) For PD-weighted imaging pulse sequences, refer to the acquisition parameters of proton density PD-weighted sequences in conventional clinical scanning sequences, set the combination of short TE parameters and long TR parameters, and acquire proton density-weighted magnetic resonance images.

[0062] (4) For T2-weighted imaging pulse sequences and diffusion-weighted imaging pulse sequences, the Stejskal-Tanner spin echo sequence is used to acquire diffusion images (or other diffusion coding methods, such as Pulsed Gradient Spin Echo); a longer TE parameter and a longer TR parameter are set. When parameter b equals 0, the magnetic resonance image can be approximated as a T2-weighted magnetic resonance image. Diffusion images in three diffusion directions are acquired to further obtain the average DWI image and ADC parameter map; in addition, diffusion tensor imaging in six diffusion directions (or more diffusion coding directions) can be performed to calculate multiple parameter maps such as anisotropy fraction FA, average diffusion MD, radial diffusion RD, and axial diffusion AD.

[0063] (5) For Weighted imaging pulse sequences, based on gradient echo sequences, are acquired using short TE parameters and relatively long TR parameters. Weighted magnetic resonance imaging.

[0064] It should be noted that the short TR parameter refers to a time range of 200-1500ms, the short TE parameter refers to a time range of less than 30ms, the long TR parameter refers to a time range of more than 2000ms, and the long TE parameter refers to a time range of more than 50ms.

[0065] Step S120: Generate a magnetic resonance signal according to the modular multi-contrast imaging pulse sequence, and acquire the magnetic resonance signal using a spiral trajectory to obtain the acquired magnetic resonance signal.

[0066] In this embodiment, the helical sampling trajectory has high encoding efficiency, and using the helical trajectory to acquire magnetic resonance signals can effectively improve the acquisition efficiency of magnetic resonance signals. When acquiring magnetic resonance signals, a parallel imaging method is used to shorten the length of the helical acquisition trajectory to reduce blur artifacts in the magnetic resonance image. Furthermore, the signal-to-noise ratio loss caused by the parallel imaging method must be considered; the acceleration factor should not be too large, otherwise the magnetic resonance imaging quality will also be affected, failing to meet practical requirements.

[0067] In one optional embodiment, the magnetic resonance signal is acquired using a helical trajectory to obtain the acquired magnetic resonance signal, including: acquiring the magnetic resonance signal using a multiple excitation method based on a downsampling acceleration strategy to obtain the acquired magnetic resonance signal; wherein, the downsampling acceleration strategy includes: a radial downsampling strategy and a helical trajectory rearrangement strategy.

[0068] Specifically, the radial reduction strategy increases the radial spacing of the spiral trajectories, enabling them to reach the outside of the k-space more quickly (i.e., rapidly fill the entire k-space), thereby shortening the acquisition time for each spiral trajectory. The spiral trajectory rearrangement strategy rearranges the spiral trajectories within the k-space, reducing the number of data acquisition triggers and thus shortening the data acquisition time.

[0069] The acquisition of magnetic resonance signals under the radial downsampling strategy and the spiral trajectory rearrangement strategy will be described below.

[0070] (1) When the reduction and acceleration strategy is a radial reduction strategy, the magnetic resonance signal is acquired by multiple excitation based on the radial reduction strategy, including: obtaining a spiral acquisition trajectory with increased radial spacing in the k space by modifying the gradient waveform of the spiral acquisition trajectory; and acquiring the magnetic resonance signal multiple times according to the spiral acquisition trajectory with increased radial spacing in the k space until a complete magnetic resonance signal distributed in the k space is obtained.

[0071] In this embodiment, the radial spacing of the helical acquisition trajectories in k-space is increased by modifying the gradient waveform of the helical trajectory, enabling the helical acquisition trajectories to reach the outside of k-space more quickly, thereby shortening the acquisition time of each helical trajectory; thus, efficient data acquisition can be achieved. Specifically, the radial downsampling strategy is optimized based on the helical acquisition trajectories with full sampling uniform sampling density, increasing the radial spacing of each helical acquisition trajectory to R times the original value.

[0072] For example, Figure 3 This is a schematic diagram of a spiral acquisition radial reduction strategy provided in an embodiment of this application. The radial spacing of the spiral acquisition trajectory with full-capacity uniform sampling density is: FOV is the field of view size in magnetic resonance imaging. Based on a radial downsampling strategy, the radial spacing of the helical acquisition trajectory is increased by a factor of R (R>1). The radial spacing of the downsampled helical acquisition trajectory becomes: Thus, the readout length of the downsampled spiral wiping trajectory is shortened to approximately 1 / R times the original readout length, thereby mitigating the problem of off-resonance artifacts caused by field inhomogeneity. Furthermore, in actual scanning, the value of R can be flexibly selected to adjust the readout length of the spiral acquisition trajectory, i.e., to adjust the length of the spiral acquisition trajectory distributed in part of the k-space.

[0073] In a specific embodiment, in order to avoid strong local modulation of k-space data in traditional interleaved spiral, a circular segmentation scheme is adopted to collect magnetic resonance signals. Specifically, according to the spiral acquisition trajectory with an increasing radial spacing in the k-space, the magnetic resonance signals are collected multiple times, including: sequentially collecting the magnetic resonance signals according to the spiral acquisition trajectory with an increasing radial spacing in the k-space in the order from the center of the k-space to the edge of the k-space. And, since the signal at the center of the k-space is the strongest, the spiral trajectory at the center of the k-space is preferentially collected, ensuring the signal-to-noise ratio of the magnetic resonance image.

[0074] (2) When the undersampling acceleration strategy is the spiral trajectory rearrangement strategy, based on the spiral trajectory rearrangement strategy, the magnetic resonance signals are collected using a multi-excitation method, including: increasing the rotation angle between the multi-excitation spiral acquisition trajectories, and the magnitude of the rotation angle is negatively correlated with the number of excitation times of the spiral acquisition trajectories required to obtain the complete magnetic resonance signals distributed in the k-space; exciting the spiral acquisition trajectories multiple times according to the rotation angle and collecting the magnetic resonance signals according to the spiral acquisition trajectories to obtain the complete magnetic resonance signals distributed in the k-space.

[0075] In the embodiments of the present application, without modifying the gradient waveform of the spiral trajectory, by increasing the rotation angle between the multi-excitation spiral acquisition trajectories to reduce the required number of excitation times, and thus reducing the acquisition time. For a spiral acquisition trajectory composed of N spiral lines, these N spiral acquisition trajectories are evenly distributed in the k-space, and each spiral acquisition trajectory rotates around the center of the k-space with a rotation angle of 2π / N. For the case where only one spiral trajectory is collected in one excitation, it is necessary to go through N excitations to obtain the spiral acquisition trajectory distributed in the entire k-space. In the embodiments of the present application, in order to reduce the number of excitation times, only n (n < N) excitations are performed to collect n spiral trajectories. In order to make these n spiral trajectories evenly distributed in the k-space, the rotation angle of these n spiral trajectories around the center of the k-space needs to be changed to 2π / n, and the rotation angle 2π / n is greater than the rotation angle 2π / N. In this way, rearranging the spiral acquisition trajectories can achieve in-slice undersampling, and the undersampling multiple R = N / n.

[0076] Exemplarily, Figure 4 FIG. is a schematic diagram of a spiral trajectory rearrangement strategy provided by an embodiment of the present application. For the spiral acquisition trajectory distributed in the entire k-space composed of 6 spiral trajectories, each spiral acquisition trajectory is spaced apart from each other by a rotation angle of π / 3. If only 4 of these 6 spiral trajectories are needed to form the spiral acquisition trajectory distributed in the entire k-space, the rotation angle between the 4 spiral trajectories needs to be adjusted to π / 2, and the corresponding undersampling multiple R = 1.5.

[0077] In this embodiment, each excitation of the multi-contrast imaging pulse sequence to generate a magnetic resonance signal only yields a portion of the helical acquisition trajectory distributed within the k-space. Therefore, it needs to be repeated multiple times until the entire helical acquisition trajectory distributed within the k-space is obtained. The number of repetitions (excitation counts) is determined based on the resolution and size of the magnetic resonance image; the higher the resolution and the larger the size of the magnetic resonance image, the more repetitions are required.

[0078] Step S130: Perform imaging reconstruction based on the acquired magnetic resonance signals to obtain magnetic resonance images with different contrasts.

[0079] In this embodiment, the magnetic resonance imaging results with different contrasts include acquired magnetic resonance images with different contrasts and other parameter maps. The magnetic resonance images with different contrasts include T1 W-FLAIR images, T2 W-FLAIR images, PD-weighted images, T2-weighted images, diffusion-weighted images, and T2... * Weighted image; other parametric images include apparent diffusion coefficient ADC, anisotropy fraction FA, mean diffusion MD, radial diffusion RD, and axial diffusion AD.

[0080] In one optional embodiment, imaging reconstruction is performed based on the acquired magnetic resonance signals to obtain magnetic resonance images with different contrasts, including: determining common information and coil sensitivity distribution information of magnetic resonance images with different contrasts based on the acquired magnetic resonance signals; and performing imaging reconstruction based on the common information and coil sensitivity distribution information of the magnetic resonance images with different contrasts to obtain magnetic resonance images with different contrasts.

[0081] In this embodiment, the common information of magnetic resonance images with different contrasts and the coil sensitivity distribution information are used to reconstruct the acquired magnetic resonance signal (i.e., the sampled magnetic resonance image) to obtain high-quality magnetic resonance images with different contrasts.

[0082] In summary, this application proposes a rapid multi-contrast magnetic resonance imaging method based on helical trajectory acquisition, leveraging the high spatial coding efficiency of helical trajectory acquisition. A modular multi-contrast imaging pulse sequence is constructed, consisting of multiple preparation modules, each generating a different magnetic resonance signal. The generated magnetic resonance signal is then acquired using a helical trajectory. Finally, imaging reconstruction is performed based on the acquired magnetic resonance signal to obtain magnetic resonance images with different contrasts. Because the helical acquisition trajectory has high spatial coding efficiency, using it to acquire magnetic resonance signals improves the acquisition efficiency, thus increasing the imaging speed of multi-contrast magnetic resonance images.

[0083] The acquisition parameters of magnetic resonance multi-contrast fast imaging based on helical trajectory acquisition in the embodiments of this application are illustrated below by way of example.

[0084] (1) At FOV = 210 × 210 mm 2 Resolution = 1.0 × 1.0 mm 2 With an acquisition matrix of 212×212, a readout time of 26.0ms for the spiral acquisition trajectory, and 24 axial layers covering the entire brain with a slice thickness of 4.0mm and a slice spacing of 1.0mm, the scan time was 16s for the T1W-FLAIR sequence, 40s for the T2W-FLAIR sequence, 15s for the PDW sequence, 11s for the T2*W sequence, and 51s for T2W and diffusion imaging in three diffusion directions with b=1000s / mm2, for a total scan time of 133s.

[0085] For example, Figure 5 This is a schematic diagram of magnetic resonance imaging results with different contrasts provided in an embodiment of this application, including six contrast magnetic resonance images and ADC parameter maps obtained by a rapid multi-contrast magnetic resonance imaging method based on helical trajectory acquisition. Multi-contrast magnetic resonance signals were acquired using a four-excitation technique, with a total scan time of 133 s. The six contrast images include T1W FLAIR, T2W, PDW, T2*W, T2W FLAIR, diffusion-weighted image with b = 1000 s / mm², averaged DWI, and ADC map.

[0086] (2) At FOV = 210 × 210 mm 2 Resolution = 1.0 × 1.0 mm 2 With an acquisition matrix of 212×212, a spiral readout time of 26.0ms, and 24 layers covering the entire brain with a slice thickness of 4.0mm and a slice spacing of 1mm, the scan time was 16s for the T1W-FLAIR sequence, 40s for the T2W-FLAIR sequence, 15s for the PDW sequence, 11s for the T2*W sequence, and 87s for T2W and diffusion imaging in 6 diffusion directions with a b=1000s / mm2. The total scan time was 169s.

[0087] Figure 6This is a schematic diagram of another magnetic resonance imaging result with different contrasts provided in an embodiment of this application, including six contrast magnetic resonance images and FA, MD, RD, and AD parameter diagrams obtained by a rapid multi-contrast magnetic resonance imaging method based on helical trajectory acquisition. Specifically, multi-contrast magnetic resonance signals are acquired using a four-excitation technique, with a total scan time of 169s. The six contrast images include T1WFLAIR, T2W, PDW, T2*W, T2WFLAIR, diffusion-weighted image with b=1000s / mm2, averaged DWI image, and parameter diagrams such as FA, MD, AD, and RD.

[0088] To reduce off-resonance artifacts and maintain the image signal-to-noise ratio, in the scanning sequences of the above examples, except for the T2*W magnetic resonance images which were acquired using a spiral trajectory with 6 excitations and full sampling, the magnetic resonance images of other contrasts were acquired using the downsampling acceleration strategy in the embodiments of this application with 4 excitations and spiral sampling.

[0089] Thus, based on the spiral trajectory acquisition-based rapid multi-contrast magnetic resonance imaging method provided in this application embodiment, on a high-field magnetic resonance system, it is possible to acquire six contrast magnetic resonance images and calculate the relevant parameter maps within approximately 2 minutes, providing a new option for rapid clinical head magnetic resonance imaging; and on a low-field magnetic resonance system (≤1.0T), it fully utilizes the high signal sampling efficiency of spiral acquisition to provide a solution for multi-contrast imaging.

[0090] This application also provides a magnetic resonance multi-contrast rapid imaging device based on spiral trajectory acquisition, referring to... Figure 7 As shown, Figure 7 This is a schematic diagram of a magnetic resonance multi-contrast rapid imaging device based on spiral trajectory acquisition provided in an embodiment of this application. The device includes:

[0091] The construction module 710 is used to construct a modular multi-contrast imaging pulse sequence consisting of multiple preparation modules, each preparation module being used to generate a different magnetic resonance signal;

[0092] The acquisition module 720 is used to generate a magnetic resonance signal based on the modular multi-contrast imaging pulse sequence, and to acquire the magnetic resonance signal using a spiral trajectory to obtain the acquired magnetic resonance signal.

[0093] The reconstruction module 730 is used to perform imaging reconstruction based on the acquired magnetic resonance signals to obtain magnetic resonance images with different contrasts.

[0094] In one alternative embodiment, the building module includes:

[0095] The device module is modified to use excitation, refocusing, and flipping radio frequency pulses, and to modify the corresponding gradient coding, and to set the repetition time and echo time, in order to obtain a preparation module with different contrasts, based on the imaging characteristics of magnetic resonance images.

[0096] The selection module is used to select the corresponding preparation module to form a modular multi-contrast imaging pulse sequence based on the magnetic resonance images of different contrasts to be acquired.

[0097] In one optional embodiment, the acquisition module includes:

[0098] The downsampling module is used to acquire the magnetic resonance signal by using a multiple excitation method based on a downsampling acceleration strategy, thereby obtaining the acquired magnetic resonance signal.

[0099] The aforementioned mining acceleration strategies include: a radial mining acceleration strategy and a spiral trajectory rearrangement strategy.

[0100] In one optional embodiment, the reduction module includes:

[0101] The gradient waveform modification module is used to obtain a spiral acquisition trajectory with increased radial spacing in k-space by modifying the gradient waveform of the spiral acquisition trajectory.

[0102] The first signal acquisition module is used to acquire the magnetic resonance signal multiple times according to the spiral acquisition trajectory with increasing radial spacing in the k-space, until the complete magnetic resonance signal distributed in the k-space is obtained.

[0103] In one optional embodiment, the first signal acquisition module includes:

[0104] The ring-shaped segmentation acquisition module is used to acquire the magnetic resonance signal in a spiral acquisition trajectory with increasing radial spacing within the k-space, following the order from the center of the k-space to the edge of the k-space.

[0105] In one optional embodiment, the reduction module includes:

[0106] An angle increasing module is used to increase the rotation angle between multiple excitations of the spiral acquisition trajectory. The magnitude of the rotation angle is negatively correlated with the number of excitations of the spiral acquisition trajectory required to obtain the complete magnetic resonance signal distributed in the k-space.

[0107] The first signal acquisition module is used to repeatedly excite the spiral acquisition trajectory according to the rotation angle, and acquire the magnetic resonance signal according to the spiral acquisition trajectory to obtain the complete magnetic resonance signal distributed in the k-space.

[0108] In one optional embodiment, the reconstruction module includes:

[0109] The determination module is used to determine the common information and coil sensitivity distribution information of magnetic resonance images with different contrasts based on the acquired magnetic resonance signals.

[0110] The reconstruction submodule is used to perform imaging reconstruction based on the common information of the magnetic resonance images with different contrasts and the coil sensitivity distribution information to obtain magnetic resonance images with different contrasts.

[0111] This application also provides an electronic device, see embodiments thereof. Figure 8 , Figure 8 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. For example... Figure 8 As shown, the electronic device 800 includes a memory 810 and a processor 820. The memory 810 and the processor 820 are connected via a bus for communication. The memory 810 stores a computer program that can run on the processor 820 to implement the steps of the magnetic resonance multi-contrast rapid imaging method based on helical trajectory acquisition described in the embodiments of this application.

[0112] This application also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the magnetic resonance multi-contrast fast imaging method based on helical trajectory acquisition described in this application.

[0113] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0114] This application describes embodiments of methods, apparatus, and devices according to embodiments of this application with reference to flowchart illustrations and / or block diagrams. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing terminal device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing terminal device, generate instructions for implementing the flowchart illustrations. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0115] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing terminal device to operate in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0116] These computer program instructions can also be loaded onto a computer or other programmable data processing terminal equipment, causing a series of operational steps to be performed on the computer or other programmable terminal equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable terminal equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0117] Although preferred embodiments of the present application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present application.

[0118] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0119] The above provides a detailed description of a magnetic resonance multi-contrast rapid imaging method and apparatus based on helical trajectory acquisition provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A rapid multi-contrast magnetic resonance imaging method based on helical trajectory acquisition, characterized in that, The method includes: A modular multi-contrast imaging pulse sequence consisting of multiple preparation modules was constructed, with each preparation module used to generate a different magnetic resonance signal; Magnetic resonance signals are generated based on the modular multi-contrast imaging pulse sequence, and the magnetic resonance signals are acquired using a helical trajectory to obtain the acquired magnetic resonance signals. This includes: acquiring the magnetic resonance signals using a multiple excitation method based on a downsampling acceleration strategy; wherein the downsampling acceleration strategy includes: a radial downsampling strategy and a helical trajectory rearrangement strategy; the radial downsampling strategy optimizes the helical acquisition trajectory with uniform sampling density at full sampling, adjusting the radial interval of each helical acquisition trajectory. The readout length of the downsampled spiral sampling trajectory is shortened to half of the original readout length. This multiplies the value of R, thus mitigating the problem of partial resonance artifacts caused by field inhomogeneity. Furthermore, in actual scanning, the value of R can be flexibly selected to adjust the readout length of the spiral acquisition trajectory, i.e., adjusting the length of the spiral acquisition trajectories distributed within a portion of the k-space. The spiral trajectory rearrangement strategy uses n spiral acquisition trajectories distributed throughout the entire k-space, with the rotation angle between the n spiral acquisition trajectories being [value missing]. The corresponding reduction factor , Before the number of excitations is reduced, each excitation only collects one spiral trajectory, and it takes N excitations to obtain the spiral collection trajectory distributed throughout the entire k space. Based on the acquired magnetic resonance signals, imaging reconstruction is performed to obtain magnetic resonance images with different contrasts.

2. The method according to claim 1, characterized in that, Constructing a modular multi-contrast imaging pulse sequence consisting of multiple preparation modules, including: Based on the imaging characteristics of magnetic resonance images, excitation, refocusing, and flipping radio frequency pulses are used, and the repetition time and echo time are set by modifying the corresponding gradient coding to obtain preparation modules with different contrasts. Based on the magnetic resonance images of different contrasts to be acquired, the corresponding preparation modules are selected to form a modular multi-contrast imaging pulse sequence.

3. The method according to claim 1, characterized in that, Based on a radial downsampling strategy, the magnetic resonance signal is acquired using a multiple excitation method, including: By modifying the gradient waveform of the spiral acquisition trajectory, a spiral acquisition trajectory with increased radial spacing in k-space is obtained; Based on the spiral acquisition trajectory with increasing radial spacing within the k-space, the magnetic resonance signal is acquired multiple times until a complete magnetic resonance signal distributed within the k-space is obtained.

4. The method according to claim 3, characterized in that, Based on the spiral acquisition trajectory with increasing radial spacing within the k-space, the magnetic resonance signal is acquired multiple times, including: The magnetic resonance signal is acquired sequentially from the center of k-space to the edge of k-space, following a spiral acquisition trajectory with increasing radial spacing within k-space.

5. The method according to claim 1, characterized in that, Based on a spiral trajectory rearrangement strategy, the magnetic resonance signal is acquired using a multiple excitation method, including: Increase the rotation angle between multiple excitation spiral acquisition trajectories, the magnitude of which is negatively correlated with the number of excitations of the spiral acquisition trajectory required to obtain the complete magnetic resonance signal distributed in k-space; The spiral acquisition trajectory is excited multiple times according to the rotation angle, and the magnetic resonance signal is acquired according to the spiral acquisition trajectory to obtain the complete magnetic resonance signal distributed in the k-space.

6. The method according to claim 1, characterized in that, Based on the acquired magnetic resonance signals, imaging reconstruction is performed to obtain magnetic resonance images with different contrasts, including: Based on the acquired magnetic resonance signals, the common information and coil sensitivity distribution information of magnetic resonance images with different contrasts are determined. Imaging reconstruction is performed based on the common information of the magnetic resonance images with different contrasts and the coil sensitivity distribution information to obtain magnetic resonance images with different contrasts.

7. A magnetic resonance multi-contrast rapid imaging device based on spiral trajectory acquisition, characterized in that, The device includes: The building module is used to construct a modular multi-contrast imaging pulse sequence consisting of multiple preparation modules, each of which is used to generate a different magnetic resonance signal. The acquisition module generates magnetic resonance signals based on the modular multi-contrast imaging pulse sequence and acquires the magnetic resonance signals using a spiral trajectory to obtain the acquired magnetic resonance signals. This includes: acquiring the magnetic resonance signals using a multiple excitation method based on a downsampling acceleration strategy; wherein the downsampling acceleration strategy includes: a radial downsampling strategy and a spiral trajectory rearrangement strategy; the radial downsampling strategy optimizes the spiral acquisition trajectory with uniform sampling density at full sampling, adjusting the radial interval of each spiral acquisition trajectory... The readout length of the downsampled spiral sampling trajectory is shortened to half of the original readout length. This multiplies the value of R, thus mitigating the problem of partial resonance artifacts caused by field inhomogeneity. Furthermore, in actual scanning, the value of R can be flexibly selected to adjust the readout length of the spiral acquisition trajectory, i.e., adjusting the length of the spiral acquisition trajectories distributed within a portion of the k-space. The spiral trajectory rearrangement strategy uses n spiral acquisition trajectories distributed throughout the entire k-space, with the rotation angle between the n spiral acquisition trajectories being [value missing]. The corresponding reduction factor , Before the number of excitations is reduced, each excitation only collects one spiral trajectory, and it takes N excitations to obtain the spiral collection trajectory distributed throughout the entire k space. The reconstruction module performs imaging reconstruction based on the acquired magnetic resonance signals to obtain magnetic resonance images with different contrasts.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the magnetic resonance multi-contrast fast imaging method based on helical trajectory acquisition as described in any one of claims 1-6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the magnetic resonance multi-contrast fast imaging method based on helical trajectory acquisition as described in any one of claims 1-6.

Images