Magnetic resonance imaging method, system, medium and product for realizing simultaneous imaging of nerve melanin and quantitative magnetic susceptibility

Abstract

The invention discloses a magnetic resonance imaging method and system for realizing simultaneous imaging of nerve melanin and quantitative magnetic susceptibility, a medium and a product. The magnetic resonance imaging method comprises the following steps: performing coverage whole-brain scanning on a detected target object by using a target gradient echo sequence; wherein the target gradient echo sequence is a three-dimensional multi-echo gradient echo sequence; echo signals of the target gradient echo sequence are rapidly collected through a compressed sensing algorithm, rapid imaging is carried out based on the collected echo signals of the target gradient echo sequence, and a reconstructed image is obtained; and carrying out image post-processing on the reconstructed image to obtain a nerve melanin graph and a quantitative magnetic susceptibility graph of the brain of the detected target object. According to the method, rapid, simultaneous and quantitative imaging of two modals of nerve melanin and quantitative magnetic susceptibility through the single sequence of the target gradient echo sequence is achieved through the combination of the target gradient echo sequence and the compressed sensing technology, the scanning time can be effectively shortened, and the image quality is not affected.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of magnetic resonance imaging, and in particular to a magnetic resonance imaging method, system, medium and product for realizing simultaneous imaging of neuromelanin and quantitative susceptibility. BACKGROUND

[0002] In the technical field of magnetic resonance imaging, neuromelanin and quantitative susceptibility imaging are two important technical means for studying the pathogenesis of neuropsychiatric diseases. The pathogenesis of Parkinson's disease and schizophrenia is closely related to abnormal dopamine pathways and excessive iron deposition. The pathogenesis of depression and Huntington's disease is closely related to abnormal dopamine and norepinephrine pathways. Hepatolenticular degeneration is mainly caused by excessive copper deposition in the lenticular nucleus. Diseases such as Alzheimer's disease, multiple sclerosis, and amyotrophic lateral sclerosis may be related to excessive iron deposition. Dopamine neurons in the substantia nigra and norepinephrine neurons in the locus coeruleus of the brainstem show high signal on T1-weighted imaging due to the high content of neuromelanin. The basal ganglia, such as the lenticular nucleus, caudate nucleus, and subthalamic nucleus, the substantia nigra, the red nucleus of the midbrain, and the dentate nucleus of the cerebellum show high signal on quantitative susceptibility maps due to the deposition of paramagnetic substances such as iron and copper, as well as the presence of hemosiderin in brain hemorrhage. Therefore, whole-brain neuromelanin and susceptibility imaging has great potential for clinical application in the diagnosis and treatment of various neuropsychiatric diseases such as Parkinson's disease, Huntington's disease, cerebrovascular disease, hepatolenticular degeneration, Alzheimer's disease, multiple sclerosis, amyotrophic lateral sclerosis, schizophrenia, and depression.

[0003] However, the current neuromelanin and quantitative susceptibility imaging techniques have some limitations. First, since previous neuromelanin and quantitative susceptibility imaging techniques require at least two different sequences, the image registration process can cause large errors and the imaging time is long. This not only limits the application of neuromelanin and quantitative susceptibility imaging in the clinical diagnosis of neuropsychiatric diseases, but also increases the scanning time of patients in the magnetic resonance instrument, affecting the efficiency of imaging, and even delaying the development of the patient's condition.

[0004] Chinese patent document CN 116528747 A discloses the use of neuromelanin-sensitive MRI as a biomarker for dopamine function, but it can only achieve neuromelanin imaging in a local area of the midbrain, cannot achieve large-scale imaging covering the whole brain, and the imaging time is more than 8 minutes; Chinese patent document CN 114994584 A discloses a multi-echo magnetization transfer magnetic resonance imaging method for simultaneously detecting iron deposition and neuromelanin content in the substantia nigra and locus coeruleus, but it can only achieve imaging of 6 echoes in a local area of the midbrain, cannot achieve large-scale imaging covering the whole brain, and the imaging time is as long as 6 minutes and 14 seconds. SUMMARY

[0005] To solve the technical problems in the background art, the application provides a magnetic resonance imaging method, system, medium and product for simultaneously imaging neuromelanin and quantitative susceptibility.

[0006] In a first aspect, the application provides a magnetic resonance imaging method for simultaneously imaging neuromelanin and quantitative susceptibility, comprising:

[0007] S1, performing full brain scanning on a target object to be measured using a target gradient echo sequence; wherein the target gradient echo sequence is a three-dimensional multi-echo gradient echo sequence;

[0008] S2, rapidly acquiring echo signals of the target gradient echo sequence using a compressed sensing algorithm, and performing fast imaging based on the acquired echo signals of the target gradient echo sequence to obtain a reconstructed image;

[0009] S3, performing image post-processing on the reconstructed image to obtain a neuromelanin map and a quantitative susceptibility map of the brain of the target object to be measured.

[0010] Preferably, the target gradient echo sequence adds a magnetization transfer contrast pulse before the three-dimensional multi-echo gradient echo sequence.

[0011] Preferably, the target gradient echo sequence further adds a gradient echo sequence for destroying a residual transverse magnetization vector after each magnetization transfer contrast pulse saturation.

[0012] Preferably, the gradient echo sequence for destroying the residual transverse magnetization vector is to completely phase disperse the transverse magnetization vector by applying a gradient field or a radio frequency pulse that can change the phase.

[0013] Preferably, the gradient echo sequence for destroying the residual transverse magnetization vector is represented as

[0014] In the formula, GRE is a gradient echo, a is a flip angle, TE is an echo time, TR is a repetition time, S represents a signal, N represents a number, H represents a hydrogen proton, T1 represents a longitudinal relaxation time, and T2* represents a transverse relaxation time.

[0015] Preferably, the magnetization transfer contrast pulse is a deviated resonance excitation binomial composite magnetization transfer contrast pulse.

[0016] Preferably, the binomial composite magnetization transfer contrast pulse is

[0017] The application discloses a method for realizing simultaneous imaging of melanin and quantitative susceptibility by using magnetic resonance imaging, and the method comprises the following steps of:

[0018] S21, performing under-sampling on input full-sampling K-space data according to a predetermined under-sampling mode to obtain original under-sampling K-space data;

[0019] S22, performing Fourier transform on the original under-sampling K-space data by using coil spatial sensitivity information and regularization information;

[0020] S23, performing reconstruction according to the under-sampling K-space data after Fourier transform to obtain a reconstructed image with artifacts;

[0021] S24, performing wavelet transform on the reconstructed image with artifacts to obtain a sparsity image representation;

[0022] S25, performing noise reduction on the sparsity image representation to obtain a noise-reduced sparsity image representation;

[0023] S26, reconstructing the noise-reduced sparsity image representation from a sparse domain to an image domain by inverse wavelet transform to obtain a noise-reduced reconstructed image;

[0024] S27, performing Fourier transform on the noise-reduced reconstructed image to obtain noise-reduced K-space data;

[0025] S28, calculating data consistency according to the noise-reduced K-space data and the original under-sampling K-space data; judging whether a preset convergence condition is reached according to the data consistency; if yes, outputting the noise-reduced reconstructed image; if no, replacing data points of the noise-reduced K-space data with data points of the original under-sampling K-space data which has high consistency with the noise-reduced K-space data to form a new under-sampling K-space data, and entering S23.

[0026] Preferably, the preset convergence condition is that or the maximum iteration number is reached; in the formula, x k +1 represents the noise-reduced reconstructed image of the k+1th iteration, x k represents the noise-reduced reconstructed image of the kth iteration, || ||2 represents an L2 norm, and ε represents an error threshold.

[0027] Preferably, the reconstructed image comprises amplitude maps and phase maps of multiple echoes.

[0028] In S3, the reconstructed image is subjected to image post-processing to obtain a melanin map and a quantitative susceptibility map of the brain of the measured target object.

[0029] reconstructing a melanin map according to the magnitude map of the first echo;

[0030] reconstructing a quantitative susceptibility map according to the magnitude maps and the phase maps of the multiple echoes.

[0031] Preferably, reconstructing a quantitative susceptibility map according to the magnitude maps and the phase maps of the multiple echoes specifically comprises:

[0032] combining the magnitude maps of the multiple echoes as a mask;

[0033] performing one-dimensional time-domain unwrapping on the phase of each voxel in the phase maps of the multiple echoes, and using non-linear fitting on the phases of each voxel in different echoes to calculate a magnetic field map;

[0034] performing spatial-domain phase unwrapping on the magnetic field map by using a Laplace method based on fast Fourier transform to obtain an unwrapped phase image;

[0035] normalizing and averaging the unwrapped phase image according to the corresponding echo time, and removing the background field in the unwrapped phase image by using a complex harmonic artifact reduction method;

[0036] calculating a quantitative susceptibility map according to the residual local field in the unwrapped phase image by using a stripe artifact reduction method.

[0037] In a second aspect, the present application further provides a magnetic resonance imaging system for simultaneously imaging melanin and quantitative susceptibility, comprising: a processor and a memory, the memory being configured to store one or more programs; and when the one or more programs are executed by the processor, the magnetic resonance imaging system is configured to implement the method for simultaneously imaging melanin and quantitative susceptibility according to any one of the first aspect.

[0038] In a third aspect, the present application further provides a computer readable storage medium having a computer program stored thereon, wherein the computer program is configured to implement the steps of the method for simultaneously imaging melanin and quantitative susceptibility according to any one of the first aspect when executed by a processor.

[0039] In a fourth aspect, the present application further provides a computer program product comprising a computer program, wherein the computer program is configured to implement the steps of the method for simultaneously imaging melanin and quantitative susceptibility according to any one of the first aspect when executed by a processor.

[0040] In the present application, the proposed magnetic resonance imaging method, system, medium and product for simultaneously imaging neuromelanin and quantitative susceptibility, through the target gradient echo sequence combined with the compressed sensing technology, realizes fast, simultaneous and quantitative imaging of neuromelanin and quantitative susceptibility through the single sequence of the target gradient echo sequence, which can effectively shorten the scanning time without affecting the image quality.

[0041] The present application can provide a fast magnetic resonance imaging method for neuropsychiatric patients who cannot tolerate long-time examination due to limb shaking, mental abnormalities and the like, thereby quickly providing intermediate information for diagnosis and effectively improving user experience. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 The flowchart of the magnetic resonance imaging method for simultaneously imaging neuromelanin and quantitative susceptibility in an embodiment of the present application.

[0043] Figure 2 The timing diagram of the target gradient echo sequence in an embodiment of the present application.

[0044] Figure 3 The neuromelanin map and the quantitative susceptibility map in an embodiment of the present application: (a) is a midbrain substantia nigra melanin map, (b) is a pontine locus ceruleus melanin map, (c) is a midbrain substantia nigra quantitative susceptibility map, (d) is a cerebellar dentate nucleus quantitative susceptibility map, (e) is a midbrain red nucleus quantitative susceptibility map, and (f) is a basal ganglia quantitative susceptibility map. DETAILED DESCRIPTION

[0045] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0046] In a first aspect, with reference to Figure 1 The present application provides a magnetic resonance imaging method for simultaneously imaging neuromelanin and quantitative susceptibility, comprising:

[0047] S1, performing full brain scanning on a target object to be measured using a target gradient echo sequence;

[0048] S2, rapidly acquiring echo signals of the target gradient echo sequence using a compressed sensing algorithm, and rapidly imaging based on the acquired echo signals of the target gradient echo sequence to obtain a reconstructed image;

[0049] S3, performing image post-processing on the reconstructed image to obtain a neuromelanin map and a quantitative susceptibility map of the brain of the target object to be measured.

[0050] The application realizes fast, simultaneous and quantitative imaging of two modalities of melanin and quantitative susceptibility by a single sequence of the target gradient echo sequence through the target gradient echo sequence combined with the compressive sensing technology, can effectively shorten the scanning time and does not affect the image quality.

[0051] The application can provide a fast magnetic resonance imaging method for neuropsychiatric patients who cannot tolerate long-time examination due to limb shaking, mental abnormalities and the like, thereby quickly providing intermediate information for diagnosis and effectively improving user experience.

[0052] It should be understood that the basic idea of the gradient echo sequence is to form an echo through the reverse of the gradient, and the phase of the magnetization vector is dispersed by using the first gradient pulse in the frequency encoding direction, and then the phase of the magnetization vector is re-aggregated by using the second gradient pulse (which can be the same width and the same amplitude) with opposite polarity, so as to generate an echo, which is called a gradient echo. The advantage of the gradient echo is that no 180° radio frequency pulse is used, it is easy to maintain the specific energy absorption rate within the safety limit, and more layers can be obtained within a certain repetition time, or the scanning time can be reduced while the same number of layers are acquired.

[0053] The principle of the compressive sensing technology is mainly that the compressive sensing theory breaks through the limitation of the Nyquist signal acquisition theory, realizes the compression of the image in the signal acquisition process through compressive sampling, and greatly improves the imaging speed. This technology is particularly effective for three-dimensional sequences.

[0054] The application can effectively reduce the scanning time through the single sequence of the target gradient echo sequence, and quickly acquire through the compressive sensing technology, so as to realize fast imaging, effectively improve the magnetic resonance imaging speed of covering the whole brain, and reduce the magnetic resonance imaging time. Moreover, compared with the traditional parallel acquisition technology, the compressive sensing technology with the same acceleration multiple is used for acquisition in the embodiment, and the signal-to-noise ratio of the reconstructed image decreases very little.

[0055] In one of the embodiments, the target gradient echo sequence is a three-dimensional multi-echo gradient echo sequence.

[0056] In a further embodiment, the target gradient echo sequence is a three-dimensional multi-echo gradient echo sequence, and a magnetization transfer contrast pulse is added before the three-dimensional multi-echo gradient echo sequence to increase the signal-to-noise ratio through magnetization transfer contrast (MTC).

[0057] It is to be understood that magnetization transfer contrast (MTC) is a special technique in magnetic resonance imaging. The precession frequency of free water is assumed to be the center frequency, and the bound water frequency range is from -2000 Hz to +2000 Hz offset from the free water precession frequency. When the protons resonate, the radio frequency transmission frequency is equal to the precession frequency of the protons. Since the precession frequency of bound water is very wide, when a radio frequency is applied with a center frequency offset (usually +1200 Hz), the protons in the bound water are excited to a saturated state, while the free water is not affected. Subsequently, due to the dynamic equilibrium state of the chemical exchange and cross relaxation between the protons in the bound water and the protons in the free water, the bound water in the saturated state will transfer the energy obtained from the radio frequency pulse to the protons in the free water at a specific exchange rate of the tissue, causing part of the free water protons to be saturated, and this part of the saturated free water will not produce a signal, thereby reducing the detected tissue signal. This process is actually the transfer of saturated magnetization state from bound water to free water, thereby reducing the free water signal.

[0058] Since the white matter region in the brain has a high content of macromolecules, the white matter region in the brain has a higher sensitivity to MTC radio frequency pulses, the MTC effect is stronger, and the signal attenuation is obvious. The gray matter region has a lower content of macromolecules than the white matter, the MTC effect is weaker than the white matter region, and the signal attenuation degree is weaker than the white matter. Due to the presence of melanin in the substantia nigra compacta of the midbrain, this paramagnetic substance shortens the relaxation time of free protons and bound protons, thereby reducing the saturation degree of the substantia nigra compacta, the MTC effect is the weakest, and the signal attenuation degree is the lowest, and the substantia nigra compacta presents a high signal on the Tl weighted image relative to the surrounding structures.

[0059] In this embodiment, a three-dimensional multi-echo gradient echo sequence is used as the scanning sequence, and a magnetization transfer contrast pulse is added before the three-dimensional multi-echo gradient echo sequence to increase the signal-to-noise ratio through magnetization transfer contrast (MTC).

[0060] In a further embodiment, the target gradient echo sequence is a three-dimensional multi-echo gradient echo sequence, and a magnetization transfer contrast pulse is added before the three-dimensional multi-echo gradient echo sequence and a gradient echo sequence for destroying the remaining transverse magnetization vector is added after each magnetization transfer contrast pulse saturation.

[0061] Since the gradient echo sequence usually uses a short repetition time, after the echo measurement is completed, the transverse magnetization vector has not decayed to zero, at this time the remaining transverse magnetization vector will affect or interfere with the signal of the next repetition time period. In order to generate a gradient echo without the effect of the remaining transverse magnetization vector, the repetition time can be increased or the remaining transverse magnetization vector can be processed. However, increasing the repetition time will result in a longer acquisition time.

[0062] The embodiment can realize fast and simultaneous quantification of brain melanin and magnetic susceptibility, and increase signal-to-noise ratio by designing a target gradient echo sequence into a three-dimensional multi-echo gradient echo sequence, adding a magnetization transfer contrast pulse before the three-dimensional multi-echo gradient echo sequence, and adding a gradient echo sequence for destroying the residual transverse magnetization vector after saturation of each magnetization transfer contrast pulse.

[0063] In one specific embodiment, the magnetization transfer contrast (MTC) pulse is a binomial composite MTC pulse with off-resonance excitation.

[0064] In the binomial composite MTC pulse, each sub-pulse is to be changed in sign. That is, the sub-pulses of the binomial composite MTC pulse with off-resonance excitation are positive and negative alternately, and are expressed as and the like.

[0065] In one specific embodiment, the binomial composite MTC pulse is

[0066] In the embodiment, the gradient echo sequence for destroying the residual transverse magnetization vector refers to that after the signal measurement is completed, the transverse magnetization vector is completely phase dispersed by applying a gradient field or a radio frequency pulse capable of causing phase change, so as to not interfere with the transverse magnetization vector of the next repetition time period.

[0067] At this time, the gradient echo signal of the gradient echo sequence for destroying the residual transverse magnetization vector is expressed as:

[0068]

[0069] In the formula, GRE is a gradient echo, α is a flip angle, TE is an echo time, TR is a repetition time, S represents a signal, N represents a number, H represents a hydrogen proton, T1 represents a longitudinal relaxation time, and T2* represents a transverse relaxation time.

[0070] The tissue signal intensity can be regarded as a function of three intrinsic tissue parameters N(H), T1 and T2*, or as a function of sequence parameters α, TE and TR. When the flip angle α is small and the TR is not too short, the short TE makes the image present a proton density weighted image, and the long TE presents a T2* weighted image; when the flip angle α is large and the TR is not too long, the short TE makes the image present a T1 weighted image.

[0071] In the embodiment, the three-dimensional gradient echo sequence has 2-10 echoes.

[0072] In a further embodiment, the number of echoes is 6-7, the TE is 4.0-7.5 ms, the TR is 55-62 ms, and the flip angle α is 18-30°.

[0073] In the embodiment, before performing the full brain scan on the target object using the target gradient echo sequence, the method further comprises:

[0074] The target gradient echo sequence is designed and generated.

[0075] In the embodiment, the echo signals of the target gradient echo sequence are rapidly acquired by using the compressed sensing algorithm, and the rapid imaging is performed based on the acquired echo signals of the target gradient echo sequence to obtain the reconstructed image, and specifically comprises:

[0076] S21, undersampling the input full-sampling K-space data according to a predetermined undersampling mode (such as random, Poisson disc) to obtain original undersampling K-space data, so as to reduce the phase encoding lines;

[0077] S22, performing Fourier transform on the original undersampling K-space data by using the coil spatial sensitivity information and the regularization information;

[0078] S23, reconstructing according to the Fourier-transformed undersampling K-space data to obtain a reconstructed image with artifacts;

[0079] S24, performing wavelet transform on the reconstructed image with artifacts to obtain a sparsity image representation;

[0080] S25, denoising the sparsity image representation to obtain a denoised sparsity image representation;

[0081] S26, reconstructing the denoised sparsity image representation from the sparse domain to the image domain by inverse wavelet transform to obtain a denoised reconstructed image;

[0082] S27, performing Fourier transform on the denoised reconstructed image to obtain denoised K-space data;

[0083] S28, calculating the data consistency according to the denoised K-space data and the original undersampling K-space data; judging whether the preset convergence condition is reached according to the data consistency, if yes, outputting the denoised reconstructed image; if no, replacing the data points of the denoised K-space data with the data points of the original undersampling K-space data which has high consistency with the denoised K-space data to form a new undersampling K-space data, and entering S23.

[0084] The preset convergence condition is to satisfy or reach the maximum iteration number; in the formula, x k+1 represents the denoised reconstructed image of the k+1th iteration, x k represents the denoised reconstructed image of the kth iteration, || ||2 represents the L2 norm, and ε represents the error threshold.

[0085] The embodiment uses a compressed sensing technology in the K-space phase encoding (Ky) and the layer selection (Kz) direction to accelerate the acquisition of echo signals of a target pulse sequence.

[0086] In the embodiment, the reconstructed image includes amplitude maps and phase maps of multiple echoes.

[0087] In the embodiment, image post-processing is performed on the reconstructed image to obtain a melanin map and a quantitative susceptibility map of the brain of the target object, specifically including:

[0088] The melanin map is reconstructed according to the amplitude map of the first echo.

[0089] The quantitative susceptibility map is reconstructed according to the amplitude maps and the phase maps of the multiple echoes.

[0090] The shorter the echo time and the higher the echo signal intensity, the more conducive to the display of melanin, so the amplitude map of the first echo is used to reconstruct the melanin map. The more the number of echoes, the more conducive to improving the accuracy of phase fitting in the field map calculation, thereby accurately restoring the quantitative value of the susceptibility map. Therefore, the amplitude maps and the phase maps of all the multiple echoes are used for the reconstruction of the quantitative susceptibility map. The embodiment is thus configured, and the melanin map and the quantitative susceptibility map of the brain of the target object can be simultaneously imaged.

[0091] In order to obtain the quantitative susceptibility map, in the embodiment, the quantitative susceptibility map is reconstructed according to the amplitude maps and the phase maps of the multiple echoes, specifically including:

[0092] The amplitude maps of the multiple echoes are combined as a mask.

[0093] The phase of each voxel in the phase maps of the multiple echoes is one-dimensionally time-domain unwrapped, and the phases of different echoes of each voxel are calculated by using nonlinear fitting to obtain a magnetic field map.

[0094] The magnetic field map is spatial-domain phase unwrapped by using a Laplace method based on a fast Fourier transform to obtain an unwrapped phase image.

[0095] The unwrapped phase image is normalized and averaged according to the corresponding echo time, and the background field in the unwrapped phase image is removed by using a complex harmonic artifact reduction method.

[0096] The quantitative susceptibility map is obtained by using a stripe artifact reduction method to perform inversion calculation according to the residual local field in the unwrapped phase image.

[0097] The melanin map in the embodiment includes a midbrain substantia nigra melanin map and a pontine locus ceruleus melanin map, and the quantitative susceptibility map includes a midbrain substantia nigra quantitative susceptibility map, a cerebellar dentate nucleus quantitative susceptibility map, a midbrain red nucleus quantitative susceptibility map, and a basal ganglia quantitative susceptibility map.

[0098] The part of the substantia nigra melanin map and the magnetic susceptibility map that is overlapped in the subsequent embodiment can be used to reconstruct the structure of the substantia nigra pars compacta subregion, the part of the substantia nigra melanin map that is more than the structure of the substantia nigra pars compacta subregion can be used to reconstruct the structure of the ventral tegmental area, and the part of the substantia nigra magnetic susceptibility map that is more than the structure of the substantia nigra pars compacta subregion can be used to reconstruct the structure of the reticulata subregion.

[0099] In a second aspect, the present application further provides a magnetic resonance imaging system for simultaneously imaging neuromelanin and quantitative magnetic susceptibility, comprising: a processor and a memory, the memory being configured to store one or more programs; when the one or more programs are executed by the processor, the steps of the magnetic resonance imaging method for simultaneously imaging neuromelanin and quantitative magnetic susceptibility according to any one of the first aspect are implemented.

[0100] In a third aspect, the present application further provides a computer readable storage medium having stored thereon a computer program, wherein the computer program is configured to implement the steps of the magnetic resonance imaging method for simultaneously imaging neuromelanin and quantitative magnetic susceptibility according to any one of the first aspect when executed by a processor.

[0101] In a fourth aspect, the present application further provides a computer program product comprising a computer program configured to implement the steps of the magnetic resonance imaging method for simultaneously imaging neuromelanin and quantitative magnetic susceptibility according to any one of the first aspect when executed by a processor.

[0102] The present application will be described in detail below with reference to specific embodiments.

[0103] Embodiment 1

[0104] The magnetic resonance imaging method for simultaneously imaging neuromelanin and quantitative magnetic susceptibility provided in the embodiment comprises:

[0105] S1, performing full brain scanning on a target object to be measured using a target gradient echo sequence; wherein the target gradient echo sequence is a three-dimensional multi-echo gradient echo sequence, and a binomial composite MTC pulse is added before the three-dimensional multi-echo gradient echo sequence and a phase-encoding gradient field is added after saturation of each binomial composite MTC pulse; wherein the specific imaging parameters of the target gradient echo sequence are as follows: TE is 7.5 ms, a total of 7 echoes, interval time is 7.5 ms; TR is 62 ms; flip angle α is 30°; field of view (FOV) is 258 mm (anterior-posterior direction, frequency encoding) x 194 mm (left-right direction, phase encoding), matrix is 384 x 144; slice thickness is 2 mm; number of layers is 150 layers; the size of the reconstructed voxel is 0.67 mm x 0.67 x 1 mm; the acquisition bandwidth of each voxel is 176 Hz; the timing diagram of the target gradient echo sequence is as shown in Figure 2 Fig. 1.

[0106] S2. The echo signal of the target gradient echo sequence is quickly acquired using the compressed sensing algorithm, and the reconstructed image is obtained by rapid imaging based on the acquired echo signal of the target gradient echo sequence. Among them, the compressed sensing technology is used to accelerate the acquisition in the K-space phase encoding (Ky) and layer selection (Kz) directions, the acceleration factor is set to 4.5, and the acquisition time is 2 minutes and 49 seconds.

[0107] S3. Perform image post-processing on the reconstructed image to obtain the neural melanin map and quantitative magnetic susceptibility map of the brain of the target object; among them, the amplitude map of the first echo is used to reconstruct the neural melanin map, and the amplitude maps and phase maps of all 7 echoes are used to reconstruct the quantitative magnetic susceptibility map.

[0108] In this embodiment, the target gradient echo sequence was implemented on Philips' sequence integration development platform, and the magnetic resonance imaging data acquisition was completed on a 3.0T Philips Ingenia CX device.

[0109] like Figure 3 As shown, (a) is a melanin map of the substantia nigra of the midbrain, (b) is a melanin map of the locus coeruleus of the pons, (c) is a quantitative magnetic susceptibility map of the substantia nigra of the midbrain, (d) is a quantitative magnetic susceptibility map of the dentate nucleus of the cerebellum, (e) is a quantitative magnetic susceptibility map of the red nucleus of the midbrain, and (f) is a quantitative magnetic susceptibility map of the basal ganglia.

[0110] This embodiment can achieve rapid and simultaneous imaging of two modes—neural melanin and quantitative magnetic susceptibility—within three minutes of a single sequence, significantly improving the acquisition efficiency of imaging.

[0111] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A magnetic resonance imaging method for simultaneous imaging of neuromelanin and quantitative susceptibility, characterized in that, The method comprises the following steps: S1, performing a full brain scan on a target object to be measured using a target gradient echo sequence; wherein the target gradient echo sequence is a three-dimensional multi-echo gradient echo sequence; S2, rapidly acquiring echo signals of the target gradient echo sequence using a compressed sensing algorithm, and performing fast imaging based on the acquired echo signals of the target gradient echo sequence to obtain a reconstructed image; S3, performing image post-processing on the reconstructed image to obtain a melanin map and a quantitative susceptibility map of the brain of the target object to be measured.

2. The method of magnetic resonance imaging enabling simultaneous imaging of neuromelanin and quantitative susceptibility according to claim 1, characterized in that, The target gradient echo sequence adds a magnetization transfer contrast pulse before the three-dimensional multi-echo gradient echo sequence.

3. The method of magnetic resonance imaging enabling simultaneous imaging of neuromelanin and quantitative susceptibility according to claim 2, characterized in that, The target gradient echo sequence further adds a gradient echo sequence for destroying the residual transverse magnetization vector after each magnetization transfer contrast pulse saturation.

4. The method of magnetic resonance imaging enabling simultaneous imaging of neuromelanin and quantitative susceptibility according to claim 3, characterized in that, The gradient echo sequence for destroying the residual transverse magnetization vector is to completely phase disperse the transverse magnetization vector by applying a gradient field or a radio frequency pulse that can change the phase; Preferably, the gradient echo sequence for destroying the residual transverse magnetization vector is represented as In the formula, GRE is a gradient echo, α is a flip angle, TE is an echo time, TR is a repetition time, S represents a signal, N represents a number, H represents a hydrogen proton, T1 represents a longitudinal relaxation time, and T2* represents a transverse relaxation time.

5. The method of magnetic resonance imaging enabling simultaneous imaging of neuromelanin and quantitative susceptibility according to any of claims 2-4, characterized in that, The magnetization transfer contrast pulse is a deviated resonance excitation binomial composite magnetization transfer contrast pulse; Preferably, the binomial composite magnetization transfer contrast pulse is 90°-180°-90° (1-2--1).

6. The method of magnetic resonance imaging enabling simultaneous imaging of neuromelanin and quantitative susceptibility according to claim 1, characterized in that, In S2, the echo signals of the target gradient echo sequence are rapidly acquired using a compressed sensing algorithm, and fast imaging is performed based on the acquired echo signals of the target gradient echo sequence to obtain a reconstructed image, which specifically comprises: S21, performing undersampling on the input full-sampling K-space data according to a predetermined undersampling mode to obtain original undersampling K-space data; S22, performing Fourier transform on the original undersampling K-space data using coil spatial sensitivity information and regularization information; S23, reconstructing according to the Fourier-transformed undersampling K-space data to obtain a reconstructed image with artifacts; S24, performing wavelet transform on the reconstructed image with artifacts to obtain a sparsity image representation; S25, performing noise reduction on the sparsity image representation to obtain a noise-reduced sparsity image representation; S26, reconstructing the noise-reduced sparsity image representation from the sparse domain to the image domain through inverse wavelet transform to obtain a noise-reduced reconstructed image; S27, performing Fourier transform on the noise-reduced reconstructed image to obtain noise-reduced K-space data; S28, calculating data consistency according to the noise-reduced K-space data and the original undersampling K-space data; determining whether a preset convergence condition is reached according to the data consistency; if yes, outputting the noise-reduced reconstructed image; if no, replacing the data points of the noise-reduced K-space data with data points of the original undersampling K-space data that have high consistency with the noise-reduced K-space data to form a new undersampling K-space data, and entering S23; Preferably, the preset convergence condition is that or a maximum iteration number is reached; where x k+1 denotes the denoised reconstructed image of the k+1th iteration, x k denotes the denoised reconstructed image of the kth iteration, || ||2denotes the L2norm, and ε denotes an error threshold.

7. The method of magnetic resonance imaging enabling simultaneous imaging of neuromelanin and quantitative susceptibility according to claim 1, characterized in that, The reconstructed image includes amplitude maps and phase maps of multiple echoes. In S3, the reconstructed image is subjected to image post-processing to obtain a melanin map and a quantitative susceptibility map of the brain of the measured target object, specifically including: According to the amplitude map of the first echo, a melanin map is reconstructed; According to the amplitude map and the phase map of the multiple echoes, a quantitative susceptibility map is reconstructed; Preferably, according to the amplitude map and the phase map of the multiple echoes, a quantitative susceptibility map is reconstructed, specifically including: Combining the amplitude maps of the multiple echoes as a mask; Performing one-dimensional time-domain unwrapping on the phase of each voxel in the phase map of the multiple echoes, and using nonlinear fitting to calculate a magnetic field map for the phase of each voxel at different echoes; Performing spatial-domain phase unwrapping on the magnetic field map using a Laplace method based on fast Fourier transform to obtain an unwrapped phase image; Normalizing and averaging the unwrapped phase image according to the corresponding echo time, and removing the background field in the unwrapped phase image through a complex harmonic artifact reduction method; Using a stripe artifact reduction method to perform inversion calculation according to the residual local field in the unwrapped phase image to obtain a quantitative susceptibility map.

8. A magnetic resonance imaging system enabling simultaneous imaging of neuromelanin and quantitative susceptibility, characterized by, Comprising: a processor and a memory, the memory being configured to store one or more programs; when the one or more programs are executed by the processor, the method for simultaneously imaging melanin and quantitative susceptibility according to any one of claims 1-7 is implemented.

9. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to implement the steps of the method for simultaneously imaging melanin and quantitative susceptibility according to any one of claims 1-7.

10. A computer program product comprising a computer program, characterized in that, The computer program is executed by the processor to implement the steps of the method for simultaneously imaging melanin and quantitative susceptibility according to any one of claims 1-7. The computer program is executed by the processor to implement the steps of the method for simultaneously imaging melanin and quantitative susceptibility according to any one of claims 1-7.

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