Extremely low field multi-core synchronous magnetic resonance imaging method, system and device and medium
Patent Information
- Application Number
- CN202510200642.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-24
- Publication Date
- 2025-06-20
Smart Images
Figure CN120178129A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the technical field of magnetic resonance imaging, and particularly relates to a very low field multi-nuclear synchronous magnetic resonance imaging method, system, device and medium. Background Art
[0002] Multi-nuclear synchronous magnetic resonance imaging technology is a technology that simultaneously or alternately utilizes multiple atomic nuclei (such as hydrogen ( 1 H), fluorine ( 19 F), sodium ( 23 Na) and / or phosphorus ( 31 P), etc.) to perform magnetic resonance imaging (MRI). By utilizing the magnetic resonance characteristics of different atomic nuclei, signals of multiple nuclides are collected, and multi-parameter images are reconstructed based on the signals of different nuclides, which not only expands the imaging range of magnetic resonance imaging, but also provides richer biochemical and metabolic information.
[0003] Current multi-nuclear synchronous magnetic resonance imaging methods usually achieve synchronous magnetic resonance imaging of different nuclides at high fields. However, the complexity of high-field MRI systems is high, and the construction cost is expensive. In particular, the multi-nuclear synchronous radio frequency transceiver and radio frequency link of high-field MRI systems are very expensive in terms of production and design costs, and metal objects are easily affected by high fields, interfering with the spatial encoding of MRI, resulting in metal artifacts being easily generated in high-field multi-nuclear magnetic resonance imaging. Although the complexity, construction cost and sensitivity to metals of very low field MRI systems are lower than those of high-field MRI systems, since the working field strength of very low field MRI systems is usually at the millitesla (mT) or even microtesla (μT) level, which is much lower than the working field strength of traditional high-field MRI systems (generally 1.5T or 3.0T), the signal intensity is weak and the signal-to-noise ratio is low. At present, except for the hydrogen nucleus with high sensitivity and high signal intensity, which can provide sufficient signals for imaging at low field strengths, other nuclides are difficult to obtain clear images under very low field conditions, resulting in the inability to achieve very low field multi-nuclear synchronous magnetic resonance imaging.
[0004] Based on this, how to achieve multi-nuclide synchronous magnetic resonance imaging at very low fields, so as to reduce the complexity and input cost of multi-nuclear synchronous magnetic resonance imaging while reducing metal artifacts in multi-nuclear magnetic resonance imaging and improving the image quality of multi-nuclear magnetic resonance imaging is an important problem that needs to be solved urgently at present. Summary of the Invention
[0005] In view of the above-mentioned disadvantages of the prior art, the purpose of this application is to provide a very low field multi-nuclear synchronous magnetic resonance imaging method, which is used to solve the problems that the existing multi-nuclear synchronous magnetic resonance imaging methods need to achieve synchronous magnetic resonance imaging of different nuclides at high fields, resulting in high complexity and input costs of multi-nuclide synchronous magnetic resonance imaging, and easy occurrence of metal artifacts, etc.
[0006] To achieve the above and other related objectives, the present invention provides a very low-field multi-nuclear synchronous magnetic resonance imaging method, including the following steps:
[0007] Improve the longitudinal magnetization vectors of each pre-imaging nuclide at very low fields; perform spatial encoding and signal acquisition on each of the pre-imaging nuclides to obtain a set of K-space signals corresponding to the imaging nuclide plane;
[0008] Obtain the total K-space data corresponding to the set of K-space signals, and fill zeros in the total K-space data; based on the zero-filled total K-space data, obtain the total frequency distribution corresponding to the imaging nuclide plane; split the total frequency distribution to obtain sub-frequency distributions corresponding to various pre-imaging nuclides; based on each of the sub-frequency distributions, obtain sub-K-space data corresponding to various pre-imaging nuclides;
[0009] Based on the sub-K-space data, perform image reconstruction on each of the pre-imaging nuclides respectively to obtain reconstructed images corresponding to each of the pre-imaging nuclides.
[0010] In an embodiment of the present invention, the splitting the total frequency distribution to obtain sub-frequency distributions corresponding to various pre-imaging nuclides includes:
[0011] Obtain the Larmor frequencies corresponding to various pre-imaging nuclides in the total frequency distribution; calculate the average value of two numerically adjacent Larmor frequencies respectively as each frequency splitting value; based on each of the frequency splitting values, split the total frequency distribution along the frequency encoding direction to obtain each of the sub-frequency distributions containing the corresponding Larmor frequencies as the sub-frequency distributions corresponding to the corresponding pre-imaging nuclides.
[0012] In an embodiment of the present invention, the performing image reconstruction on each of the pre-imaging nuclides respectively based on the sub-K-space data to obtain reconstructed images corresponding to each of the pre-imaging nuclides includes:
[0013] Obtain the mass numbers of the pre-imaging nuclides corresponding to each of the sub-K-space data;
[0014] Among each of the sub-K-space data, take the sub-K-space data with the smallest mass number as the reference sub-K-space data, and the other sub-K-space data as the sub-K-space data to be filled with zeros;
[0015] For each of the to-be-zero-filled sub-K space data, calculate the ratio between the gyromagnetic ratio of the pre-imaging nuclide corresponding to the to-be-zero-filled sub-K space data and the gyromagnetic ratio of the pre-imaging nuclide corresponding to the reference sub-K space data as the total number of zeros to be filled for the to-be-zero-filled sub-K space data; based on the total number of zeros to be filled, according to a preset zero-filling rule, perform zero-filling on the to-be-zero-filled sub-K space data along the phase encoding direction and the frequency encoding direction respectively to obtain each zero-filled sub-K space data;
[0016] Perform inverse Fourier transform on the reference sub-K space data and each zero-filled sub-K space data respectively to obtain the reconstructed images corresponding to various pre-imaging nuclides.
[0017] In an embodiment of the present invention, the performing inverse Fourier transform on the reference sub-K space data and each zero-filled sub-K space data respectively to obtain the reconstructed images corresponding to various pre-imaging nuclides includes:
[0018] Perform the inverse Fourier transform on the reference sub-K space data to obtain the reference reconstructed image corresponding to the reference sub-K space data; and perform the inverse Fourier transform on each zero-filled sub-K space data respectively to obtain the zero-filled reconstructed images corresponding to each zero-filled sub-K space data;
[0019] According to the image size of the reference reconstructed image, extract the central region from each zero-filled reconstructed image as the central image; use the reference reconstructed image and each central image as the reconstructed images corresponding to the corresponding pre-imaging nuclides respectively.
[0020] In an embodiment of the present invention, enhancing the longitudinal magnetization vectors of various pre-imaging nuclides at extremely low fields through prepolarization includes:
[0021] Apply a prepolarization magnetic field with a preset first duration along the direction parallel to the static magnetic field to enhance the magnetization vectors of various pre-imaging nuclides in the imaging region, so that the magnetization vectors are arranged along the magnetic field direction of the static magnetic field; or,
[0022] Apply the prepolarization magnetic field with the preset first duration along the direction perpendicular to the static magnetic field to make the magnetization vectors of various pre-imaging nuclides generate magnetization vectors arranged along the magnetic field direction of the prepolarization magnetic field; within a preset second duration before the prepolarization magnetic field is turned off, apply an adiabatic pulse with a preset third duration along the direction parallel to the static magnetic field to transfer the magnetization vectors of various pre-imaging nuclides from the magnetic field direction perpendicular to the static magnetic field to the magnetic field direction parallel to the static magnetic field.
[0023] In an embodiment of the present invention, the implementation manner of the spatial encoding and signal acquisition includes:
[0024] Before signal acquisition, a first gradient magnetic field is applied to the pre-imaging nuclides along the slice selection direction. Under the action of the first gradient magnetic field, radio frequency pulses with a preset frequency and bandwidth are applied to each of the pre-imaging nuclides, and the nuclide layer formed by the pre-imaging nuclides excited by the radio frequency pulses is used as the imaging nuclide plane; and, a second gradient magnetic field is applied to the imaging nuclide plane along the phase encoding direction to enable the pre-imaging nuclides at different positions in the phase encoding direction to accumulate corresponding phases.
[0025] During signal acquisition, a third gradient magnetic field is applied to the imaging nuclide plane along the frequency encoding direction to enable the pre-imaging nuclides at different positions in the frequency encoding direction to have corresponding resonance frequencies, so as to acquire the K-space signals corresponding to each of the pre-imaging nuclides in the imaging nuclide plane; the K-space signals reflect the positions of the pre-imaging nuclides in the phase encoding direction and the frequency encoding direction.
[0026] In an embodiment of the present invention, obtaining the total K-space data corresponding to the K-space signal set and padding zeros to the total K-space data includes:
[0027] Performing K-space filling on each of the K-space signals in the K-space signal set to obtain the total K-space data corresponding to the K-space signal set; padding zeros to the total K-space data according to a preset zero-padding multiple to obtain the zero-padded total K-space data.
[0028] Correspondingly, the present invention provides a very low-field multi-nuclear synchronous magnetic resonance imaging system, including:
[0029] A signal acquisition module, configured to increase the longitudinal magnetization vectors of each of the pre-imaging nuclides under very low field; perform spatial encoding and signal acquisition on each of the pre-imaging nuclides to obtain a K-space signal set corresponding to the imaging nuclide plane in the pre-imaging nuclides;
[0030] A K-space data acquisition module, configured to obtain the total K-space data corresponding to the K-space signal set, and padding zeros to the total K-space data; based on the zero-padded total K-space data, obtain the total frequency distribution corresponding to the imaging nuclide plane; split the total frequency distribution to obtain sub-frequency distributions corresponding to various types of pre-imaging nuclides; based on each of the sub-frequency distributions, obtain sub-K-space data corresponding to various types of pre-imaging nuclides;
[0031] A synchronous imaging module, configured to perform image reconstruction on various types of the pre-imaging nuclides respectively based on the sub-K-space data to obtain reconstructed images corresponding to various types of the pre-imaging nuclides.
[0032] Correspondingly, the present invention provides a computer device, including:
[0033] A memory for storing a computer program;
[0034] A processor for executing the computer program stored in the memory, so that the device executes the very low field multi-nuclear synchronous magnetic resonance imaging method as described above.
[0035] Correspondingly, the present invention provides a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the very low field multi-nuclear synchronous magnetic resonance imaging method as described above is implemented.
[0036] As described above, a very low field multi-nuclear synchronous magnetic resonance imaging method, system, device and medium provided by the present application have at least the following beneficial effects:
[0037] By increasing the longitudinal magnetization vectors of the pre-imaging nuclides in a very low field, the signal intensities of the pre-imaging nuclides in the very low field are increased; spatial encoding and signal acquisition are performed on the pre-imaging nuclides with increased signal intensities to obtain a set of K-space signals corresponding to the imaging nuclide plane in the pre-imaging nuclides; and, by obtaining the total K-space data corresponding to the set of K-space signals, zero-padding is performed on the total K-space data; based on the zero-padded total K-space data, the total frequency distribution corresponding to the imaging nuclide plane is obtained; by splitting the total frequency distribution, sub-frequency distributions corresponding to various pre-imaging nuclides are obtained; based on the sub-frequency distributions, sub-K-space data corresponding to various pre-imaging nuclides are obtained; based on the sub-K-space data, image reconstruction is respectively performed on various pre-imaging nuclides to obtain reconstructed images corresponding to various pre-imaging nuclides. The method can synchronously excite and acquire magnetic resonance signals of multiple nuclides without changing the hardware configuration of the very low field MRI system, realize synchronous magnetic resonance imaging of multiple pre-imaging nuclides, not only reduce the complexity and investment cost of multi-nuclear synchronous magnetic resonance imaging, but also greatly reduce the acquisition time and metal artifacts of multi-nuclear magnetic resonance imaging, improve the image quality of multi-nuclear magnetic resonance imaging, and expand the application scenarios of very low field MRI. BRIEF DESCRIPTION OF THE DRAWINGS
[0038] Figure 1 It shows a schematic flowchart of a very low field multi-nuclear synchronous magnetic resonance imaging method provided by the present application in an embodiment.
[0039] Figure 2 It shows a schematic diagram of a very low field magnetic resonance imaging pulse sequence based on spin echo provided by the present application.
[0040] Figure 3 A schematic structural diagram of a very low field multi-nuclear synchronous magnetic resonance imaging system provided by the present application in an embodiment.
[0041] Figure 4 Schematic diagram of modules of a computer device provided by the present application in an embodiment is shown.
[0042] Description of reference numerals
[0043] S1 to S3, steps; 200, very low field multi-nuclear synchronous magnetic resonance imaging system; 201, signal acquisition module; 202, K-space data acquisition module; 203, synchronous imaging module; 300, device; 301, memory; 302, processor; B p , prepolarizing magnetic field; B1, radio frequency pulse; G x , slice selection gradient; G y , phase encoding gradient; G z , frequency encoding gradient; SQUID Singnal, SQUID output signal; TR, repetition time; TE, echo time; TA, signal acquisition time. Detailed implementation manners
[0044] The following uses specific specific examples to illustrate the implementation manners of the present application. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. The present application can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.
[0045] It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present application in a schematic manner. Therefore, only the components related to the present application are shown in the drawings, rather than being drawn according to the number, shape, and size of the components in actual implementation. The types, quantities, and proportions of the components in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.
[0046] For the convenience of understanding the technical solutions provided by the present application, relevant terms in the present application are interpreted before the specific embodiments, as follows:
[0047] Longitudinal magnetization vector: the vector sum of magnetic moments in the direction of the static magnetic field.
[0048] Hyperpolarization: refers to pushing the nuclear spin state away from the thermodynamic equilibrium state through physical or chemical methods, thereby significantly increasing the magnetic resonance signal intensity.
[0049] Prepolarization: refers to a method of applying a high-field magnetic field to a sample before imaging to pre-polarize the nuclear magnetic moment, thereby increasing the longitudinal magnetization intensity.
[0050] Adiabatic Pulse: A radiofrequency pulse used in magnetic resonance imaging (MRI) that can maintain the direction of the nuclear spin magnetization vector consistent with the effective magnetic field direction when the magnetic field strength or direction changes.
[0051] K-space: A space that stores the raw magnetic resonance data, which contains the spatial frequency information of the imaging object.
[0052] The following will describe the embodiments of the present application in detail with reference to the accompanying drawings. Without conflict, the features in the following embodiments and implementation manners can be combined with each other.
[0053] The following embodiments of the present application provide a very low-field multi-nuclear synchronous magnetic resonance imaging method. By increasing the longitudinal magnetization vectors of the pre-imaging nuclides at very low fields, the signal intensities of the pre-imaging nuclides at very low fields are increased; spatial encoding and signal acquisition are performed on the pre-imaging nuclides with increased signal intensities to obtain the K-space signal set corresponding to the imaging nuclide plane among the pre-imaging nuclides; and, by obtaining the total K-space data corresponding to the K-space signal set, zero-padding is performed on the total K-space data; based on the zero-padded total K-space data, the total frequency distribution corresponding to the imaging nuclide plane is obtained; by splitting the total frequency distribution, the sub-frequency distributions corresponding to various pre-imaging nuclides are obtained; based on the sub-frequency distributions, the sub-K-space data corresponding to various pre-imaging nuclides are obtained; based on the sub-K-space data, image reconstruction is respectively performed on various pre-imaging nuclides to obtain the reconstructed images corresponding to various pre-imaging nuclides. The method can synchronously excite and collect the magnetic resonance signals of multiple nuclides without changing the hardware configuration of the very low-field MRI system, realizing the synchronous magnetic resonance imaging of multiple pre-imaging nuclides. It not only reduces the complexity and investment cost of multi-nuclear synchronous magnetic resonance imaging, but also greatly reduces the acquisition time and metal artifacts of multi-nuclear magnetic resonance imaging, improves the image quality of multi-nuclear magnetic resonance imaging, and expands the application scenarios of very low-field MRI.
[0054] Please refer to Figure 1 , which shows a schematic flow chart of a very low-field multi-nuclear synchronous magnetic resonance imaging method provided by the present invention in an embodiment.
[0055] As Figure 1 shown, in this embodiment, the very low-field multi-nuclear synchronous magnetic resonance imaging method provided by the present invention includes the following steps:
[0056] Step S1: Increase the longitudinal magnetization vectors of the pre-imaging nuclides at very low fields; perform spatial encoding and signal acquisition on the pre-imaging nuclides to obtain the K-space signal set corresponding to the imaging nuclide plane among the pre-imaging nuclides;
[0057] Among them, the pre-imaging nuclides have different categories;
[0058] The K-space signals collectively include: K-space signals corresponding one by one to each of the pre-imaging nuclides in the imaging nuclide plane; the K-space signals have frequency encoding and phase encoding.
[0059] Specifically, a preset polarization enhancement method is adopted to increase the longitudinal magnetization vectors of each pre-imaging nuclide at extremely low fields, so as to increase the magnetization vectors of each of the pre-imaging nuclides in the imaging region, and make the magnetization vectors arranged along the magnetic field direction of the static magnetic field; before signal acquisition, a first gradient magnetic field is applied to the pre-imaging nuclides along the slice selection direction, so that each of the pre-imaging nuclides in the slice selection direction has different resonance frequencies. Under the action of the first gradient magnetic field, a radio frequency pulse with a preset frequency and bandwidth is applied to each of the pre-imaging nuclides to excite the pre-imaging nuclides corresponding to the radio frequency pulse with the preset frequency and bandwidth, and the nuclide layer formed by the excited pre-imaging nuclides is used as the imaging nuclide plane; and, a second gradient magnetic field is applied to the imaging nuclide plane along the phase encoding direction, so that the pre-imaging nuclides at different positions in the phase encoding direction accumulate corresponding phases, realizing the phase encoding of each of the pre-imaging nuclides in the imaging nuclide plane; during signal acquisition, a third gradient magnetic field is applied to the imaging nuclide plane along the frequency encoding direction, so that the pre-imaging nuclides at different positions in the frequency encoding direction have corresponding resonance frequencies, realizing the frequency encoding of each of the pre-imaging nuclides in the imaging nuclide plane, and acquiring the K-space signals corresponding to each of the pre-imaging nuclides in the imaging nuclide plane; each of the K-space signals reflects the positions of the corresponding pre-imaging nuclides in the phase encoding direction and the frequency encoding direction; the preset frequency and bandwidth respectively determine the position and thickness of the imaging nuclide plane.
[0060] Optionally, the pre-imaging nuclides include: 1 H, 19 F, 23 Na and / or 31 P, etc.
[0061] Optionally, the polarization enhancement method includes: hyperpolarization or prepolarization and other methods.
[0062] In one embodiment, by prepolarization, the longitudinal magnetization vectors of each pre-imaging nuclide at the extremely low field are increased, including: applying a prepolarization magnetic field with a preset first duration along the direction parallel to the static magnetic field to increase the magnetization vectors of each of the pre-imaging nuclides in the imaging region, and making the magnetization vectors arranged along the magnetic field direction of the static magnetic field.
[0063] Optionally, the preset first duration is greater than or equal to 100 ms.
[0064] Optionally, the magnetic field strength of the pre-polarizing magnetic field is higher than the magnetic field strength of the static magnetic field by a preset multiple.
[0065] Exemplarily, the preset multiple includes 100.
[0066] In another embodiment, to increase the longitudinal magnetization vectors of the pre-imaging nuclides at an extremely low field through pre-polarization, it further includes: applying the pre-polarizing magnetic field with the preset first duration along a direction perpendicular to the static magnetic field, so that the magnetization vectors of the pre-imaging nuclides in the imaging region are arranged along the magnetic field direction of the pre-polarizing magnetic field; within a preset second duration before the pre-polarizing magnetic field is turned off, applying an adiabatic pulse with a preset third duration along a direction parallel to the static magnetic field, so that the magnetization vectors of the pre-imaging nuclides are transferred from the magnetic field direction perpendicular to the static magnetic field to the magnetic field direction parallel to the static magnetic field.
[0067] Optionally, the preset second duration is less than the preset third duration.
[0068] Optionally, the preset second duration includes: 5 ms; the preset third duration includes: 15 ms.
[0069] Optionally, the slice selection direction is the X-axis direction, the phase encoding direction is the Y-axis direction, and the frequency encoding direction is the Z-axis direction.
[0070] Optionally, a preset pulse sequence is used to perform spatial encoding on the pre-imaging nuclides; wherein, the pulse sequence includes a combination of radio frequency pulses and gradient magnetic fields, which is used to control the behavior of nuclear spins and generate image signals; the radio frequency pulses of the pulse sequence include: radio frequency pulses that can excite the resonance frequencies of the pre-imaging nuclides in the imaging region.
[0071] Optionally, when performing two-dimensional imaging, the range of the full width at half maximum of the radio frequency pulse includes: [Υmin - 0.5 * γ min * Gsamp * Th, Υmax + 0.5 * γ max * Gsamp * Th], in the unit of Hz; where Υmin is the minimum value of the Larmor frequency among the pre-imaging nuclides, Υmax is the maximum value of the Larmor frequency among the pre-imaging nuclides, γmin is the minimum value of the gyromagnetic ratio among the pre-imaging nuclides, γmax is the maximum value of the gyromagnetic ratio among the pre-imaging nuclides, Gsamp is the intensity value of the slice selection gradient pulse, and Th is the thickness of the imaging nuclide plane.
[0072] Optionally, when performing three-dimensional imaging, the radio frequency pulse includes: a short-duration, wide-bandwidth, and high-amplitude hard pulse that can simultaneously excite multiple frequencies.
[0073] Optionally, the pulse sequence includes: spin echo sequence, gradient echo sequence, fast spin echo sequence, echo planar imaging sequence steady state free precession, and / or diffusion weighted imaging sequence, etc.
[0074] Exemplarily, the pre-imaging nuclides include: 1 H and 19 F. A SINC pulse with three lobes is used as the radio frequency pulse; the 1 Larmor frequency of H and the 19 Larmor frequency of F, the median Larmor frequency between them, is used as the carrier frequency of the SINC pulse; the frequency bandwidth of the SINC pulse is 800 Hz, and the bandwidth of the SINC pulse is 5 ms, covering all the 1 H and 19 resonance frequencies of F. To avoid the saturation effect in the overlapping part between different layers, an interleaved layer excitation order is adopted to excite the pre-imaging nuclides.
[0075] It should be noted that in practical applications, existing spatial encoding and signal acquisition methods can be used to perform spatial encoding and signal acquisition on each of the pre-imaging nuclides to obtain K-space signals. This application does not make any limitations here.
[0076] Exemplarily, as Figure 2 shown, it is a schematic diagram of a pulse sequence based on a spin echo sequence.
[0077] Exemplarily, the carrier frequency of the SINC pulse includes: 5053 Hz.
[0078] Exemplarily, the magnetic field strength of the first gradient magnetic field includes: 300 μT / m.
[0079] Exemplarily, the thickness of the imaging nuclide plane includes: 10 mm.
[0080] Exemplarily, the K-space signals include: spin echo signals, and a highly sensitive superconducting quantum interference sensor is used to collect the spin echo signals.
[0081] Step S2: Obtain the total K-space data corresponding to the K-space signal set, and zero-pad the total K-space data; based on the zero-padded total K-space data, obtain the total frequency distribution corresponding to the imaging nuclide plane; split the total frequency distribution to obtain the sub-frequency distributions corresponding to various pre-imaging nuclides; based on each of the sub-frequency distributions, obtain the sub-K-space data corresponding to various pre-imaging nuclides;
[0082] Specifically, for each of the K-space signals in the K-space signal set, perform K-space filling to obtain the total K-space data corresponding to the K-space signal set; zero-pad the total K-space data according to a preset zero-padding multiple to obtain the zero-padded total K-space data; perform Fourier transform on the zero-padded total K-space data along the frequency encoding direction to obtain the total frequency distribution of all pre-imaging nuclides in the imaging nuclide plane; split the total frequency distribution according to a preset frequency splitting method to obtain the sub-frequency distributions corresponding to various categories of pre-imaging nuclides in the imaging nuclide plane; perform inverse Fourier transform on each of the sub-frequency distributions along the frequency encoding direction to obtain the sub-K-space data corresponding to various categories of pre-imaging nuclides.
[0083] Optionally, obtaining the sub-K-space data corresponding to various categories of pre-imaging nuclides based on each of the sub-frequency distributions includes:
[0084] Based on the sub-frequency distributions, obtain the initial sub-K-space data corresponding to various categories of pre-imaging nuclides; extract the central data of each of the initial sub-K-space data along the frequency encoding direction as the sub-K-space data corresponding to various categories of pre-imaging nuclides; the total number of data points of the central data is the same as the total number of data points of the total K-space data, and the data point at the central position of the central data in the frequency encoding direction is the data point at the central position of the initial sub-K-space data in the frequency encoding direction.
[0085] Optionally, the implementation method of the K-space filling includes:
[0086] Based on the frequency encoding and the phase encoding corresponding to the K-space signal, fill each of the K-space signals into the K-space matrix according to a preset K-space encoding order.
[0087] Optionally, the frequency distribution splitting method includes:
[0088] Obtain the Larmor frequencies corresponding to various categories of the pre-imaging nuclides in the total frequency distribution; calculate the average value of two numerically adjacent Larmor frequencies as each frequency splitting value; based on each of the frequency splitting values, split the total frequency distribution along the frequency encoding direction to obtain each of the sub-frequency distributions containing the corresponding Larmor frequencies as the sub-frequency distributions corresponding to the corresponding categories of the pre-imaging nuclides.
[0089] Optionally, zero-padding the total K-space data includes:
[0090] Obtain the original spatial size of the total K-space data; based on the original spatial size and the zero-padding multiple, obtain the total zero-padding spatial size; based on the total zero-padding spatial size, uniformly pad zeros on both sides of the total K-space data along the frequency-encoding direction to maintain the conjugate symmetry of the zero-padded total K-space data.
[0091] Optionally, the K-space encoding order includes: Cartesian, radial, spiral, or EPI encoding orders, etc.
[0092] Optionally, the zero-padding multiple is set according to the target frequency resolution.
[0093] Exemplarily, the zero-padding multiple includes: 2 times and above.
[0094] Optionally, the frequency transformation includes: Fourier transform; the inverse frequency transformation includes: inverse Fourier transform.
[0095] Step S3: Based on the sub-K-space data, perform image reconstruction on each type of the pre-imaging nuclides respectively to obtain the reconstructed images corresponding to each type of the pre-imaging nuclides.
[0096] Specifically, obtain the mass number of the pre-imaging nuclide corresponding to each sub-K-space data; among each sub-K-space data, take the sub-K-space data with the smallest mass number as the reference sub-K-space data, and the other sub-K-space data as the sub-K-space data to be zero-padded; for each sub-K-space data to be zero-padded, calculate the ratio between the gyromagnetic ratio of the pre-imaging nuclide corresponding to the sub-K-space data to be zero-padded and the gyromagnetic ratio of the pre-imaging nuclide corresponding to the reference sub-K-space data as the total number of zeros to be padded for the sub-K-space data to be zero-padded; based on the total number of zeros to be padded, according to the preset zero-padding rule, pad zeros on both sides of the sub-K-space data to be zero-padded along the phase-encoding direction and the frequency-encoding direction respectively to obtain each zero-padded sub-K-space data; perform inverse Fourier transform on the reference sub-K-space data and each zero-padded sub-K-space data respectively to obtain the reconstructed images corresponding to each type of the pre-imaging nuclides.
[0097] Optionally, the zero-padding rule includes: uniformly pad zeros on both sides of the sub-K-space data to be zero-padded along the current zero-padding direction.
[0098] Optionally, the performing inverse Fourier transform on the reference sub-K-space data and each zero-padded sub-K-space data respectively to obtain the reconstructed images corresponding to each type of the pre-imaging nuclides includes:
[0099] Performing the inverse Fourier transform on the reference sub-K space data to obtain a reference reconstructed image corresponding to the reference sub-K space data; and respectively performing the inverse Fourier transform on each of the zero-padded sub-K space data to obtain a zero-padded reconstructed image corresponding to each of the zero-padded sub-K space data;
[0100] According to the image size of the reference reconstructed image, in each of the zero-padded reconstructed images, extracting a central region as a central image; using the reference reconstructed image and each of the central images as reconstructed images of the corresponding pre-imaging radionuclides of each category; wherein, the central image is located in the central region of the zero-padded reconstructed image, and the image size of the central image is the same as the image size of the reference reconstructed image.
[0101] In this embodiment, by obtaining a reference reconstructed image corresponding to the reference sub-K space data and zero-padded reconstructed images corresponding to each of the zero-padded sub-K space data; according to the image size of the reference reconstructed image, extracting the central region of each of the to-be-zero-padded reconstructed images to obtain a central image, and using the reference reconstructed image and the central image as reconstructed images of the corresponding pre-imaging radionuclides of each category, it is possible to make the digital resolutions of the reconstructed images of each obtained nuclide consistent. With pixel positions corresponding one by one, image registration of multiple nuclides can be achieved, which helps to improve the registration efficiency of the reconstructed images of multiple nuclides.
[0102] In the extremely low-field multi-nuclear synchronous magnetic resonance imaging method provided in the above embodiment, by increasing the longitudinal magnetization vectors of each pre-imaging radionuclide at extremely low fields, the signal intensities of each of the pre-imaging radionuclides at extremely low fields are increased; performing spatial encoding and signal acquisition on each of the pre-imaging radionuclides with increased signal intensities to obtain a set of K space signals corresponding to the imaging nuclide plane in the pre-imaging radionuclides; and by obtaining the total K space data corresponding to the set of K space signals, zero-padding the total K space data; based on the zero-padded total K space data, obtaining the total frequency distribution corresponding to the imaging nuclide plane; by splitting the total frequency distribution, obtaining sub-frequency distributions corresponding to various pre-imaging radionuclides; based on each of the sub-frequency distributions, obtaining sub-K space data corresponding to various pre-imaging radionuclides; based on the sub-K space data, respectively performing image reconstruction on various pre-imaging radionuclides to obtain reconstructed images corresponding to various pre-imaging radionuclides. The method can synchronously excite and acquire magnetic resonance signals of multiple radionuclides without changing the hardware configuration of the extremely low-field MRI system, realizing synchronous magnetic resonance imaging of multiple pre-imaging radionuclides. It not only reduces the complexity and investment cost of multi-nuclear synchronous magnetic resonance imaging, but also greatly reduces the acquisition time and metal artifacts of multi-nuclear magnetic resonance imaging, improves the image quality of multi-nuclear magnetic resonance imaging, and expands the application scenarios of extremely low-field MRI.
[0103] Such as Figure 3As shown, in this embodiment, the present invention provides a very low field multi-nuclear synchronous magnetic resonance imaging system, including:
[0104] A signal acquisition module 201, configured to enhance the longitudinal magnetization vectors of various pre-imaging nuclides in a very low field; perform spatial encoding and signal acquisition on each of the pre-imaging nuclides to obtain a set of K-space signals corresponding to the imaging nuclide plane in the pre-imaging nuclides;
[0105] A K-space data acquisition module 202, configured to obtain the total K-space data corresponding to the set of K-space signals, zero-fill the total K-space data; based on the zero-filled total K-space data, obtain the total frequency distribution corresponding to the imaging nuclide plane; split the total frequency distribution to obtain sub-frequency distributions corresponding to various pre-imaging nuclides; based on each of the sub-frequency distributions, obtain sub-K-space data corresponding to various pre-imaging nuclides;
[0106] A synchronous imaging module 203, configured to perform image reconstruction on various pre-imaging nuclides respectively based on the sub-K-space data to obtain reconstructed images corresponding to various pre-imaging nuclides.
[0107] Please refer to Figure 4 , which shows a schematic structural diagram of a computer device provided by the present invention in an embodiment;
[0108] As Figure 4 shown, in this embodiment, the device 300 provided by the present invention includes a memory 301 and a processor 302. The memory 301 is used to store a computer program; the processor 302 is used to execute the computer program stored in the memory 301 so that the device 300 executes the very low field multi-nuclear synchronous magnetic resonance imaging method of any of the above embodiments of the present application. Since the specific implementation process of the steps of the very low field multi-nuclear synchronous magnetic resonance imaging method has been described in detail in the above embodiments, it will not be repeated here.
[0109] The memory 301 includes: various media such as ROM (Read Only Memory image), RAM (Random Access Memory), magnetic disk, USB flash drive, memory card, or optical disc that can store program codes.
[0110] The processor 302 is connected to the memory 301 and is used to execute the computer program stored in the memory 301 so that the device 300 executes the above-mentioned very low field multi-nuclear synchronous magnetic resonance imaging method.
[0111] The embodiments of the present application also provide a computer-readable storage medium. Those of ordinary skill in the art can understand that all or part of the steps in the methods of the above embodiments can be completed by instructing a processor through a program. The program can be stored in a computer-readable storage medium. The storage medium is a non-transitory medium, such as random access memory, read-only memory, flash memory, hard disk, solid state drive, magnetic tape, floppy disk, optical disc, and any combination thereof. The above storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or a data center integrating one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., digital video disc (DVD)), or a semiconductor medium (e.g., solid state disk (SSD)), etc.
[0112] The embodiments of the present application can also provide a computer program product, which includes one or more computer instructions. When the computer instructions are loaded and executed on a computing device, all or part of the processes or functions described in the embodiments of the present application are generated. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from a website, a computer, or a data center to another website, a computer, or a data center in a wired manner (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or a wireless manner (such as infrared, wireless, microwave, etc.).
[0113] When the computer program product is executed by a computer, the computer executes the methods described in the foregoing method embodiments. The computer program product can be a software installation package. In the case where the foregoing methods are needed, the computer program product can be downloaded and executed on the computer.
[0114] The descriptions of the processes or structures corresponding to the above respective drawings have their own focuses. For parts not detailed in a certain process or structure, reference can be made to the relevant descriptions of other processes or structures.
[0115] The above embodiments are only illustrative of the principles and effects of the present application and are not used to limit the present application. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes completed by those of ordinary skill in the art in the technical field without departing from the spirit and technical ideas disclosed by the present application should still be covered by the claims of the present application.
Claims
1. A very low field multi-nuclear synchronous magnetic resonance imaging method, characterized in that: include: Improving the longitudinal magnetization vector of each pre-imaging nuclide under extremely low field; performing spatial encoding and signal acquisition on each of the pre-imaging nuclides to obtain a K-space signal set corresponding to the imaging nuclide plane; Acquire total K-space data corresponding to the K-space signal set, and fill the total K-space data with zeros; obtain the total frequency distribution corresponding to the imaging nuclide plane based on the total K-space data after zero filling; split the total frequency distribution to obtain sub-frequency distributions corresponding to various types of pre-imaging nuclides; obtain sub-K-space data corresponding to various types of pre-imaging nuclides based on each of the sub-frequency distributions; Based on the sub-K space data, image reconstruction is performed on each type of the pre-imaging nuclides respectively to obtain reconstructed images corresponding to each type of the pre-imaging nuclides.
2. The method according to claim 1, characterized in that: The splitting of the total frequency distribution to obtain sub-frequency distributions corresponding to various types of pre-imaging nuclides includes: The Larmor frequencies corresponding to the pre-imaging nuclides of each category in the total frequency distribution are obtained; the average values of two numerically adjacent Larmor frequencies are respectively calculated as the frequency splitting values; based on the frequency splitting values, the total frequency distribution is split along the frequency coding direction to obtain the sub-frequency distributions containing the corresponding Larmor frequencies as the sub-frequency distributions of the pre-imaging nuclides of the corresponding categories.
3. The method according to claim 1, characterized in that The step of reconstructing images of various types of pre-imaging nuclides based on the sub-K-space data to obtain reconstructed images corresponding to various types of pre-imaging nuclides includes: Acquiring the mass number of the pre-imaging nuclide of the corresponding category of each sub-K-space data; The sub-K space data with the smallest quality number among the sub-K space data is used as the reference sub-K space data, and the other sub-K space data is used as the sub-K space data to be filled with zeros; For each of the sub-K-space data to be filled with zero, the ratio between the gyroscopic ratio of the pre-imaging nuclide of the category corresponding to the sub-K-space data to be filled with zero and the gyroscopic ratio of the pre-imaging nuclide of the category corresponding to the reference sub-K-space data is calculated as the total number of zero-filling of the sub-K-space data to be filled with zero; based on the total number of zero-filling, the sub-K-space data to be filled with zero is filled along the phase encoding direction and the frequency encoding direction according to a preset zero-filling rule to obtain each of the sub-K-space data after zero-filling; The reference sub-K space data and each of the zero-filled sub-K space data are respectively subjected to inverse Fourier transformation to obtain a reconstructed image corresponding to each type of the pre-imaging nuclide.
4. The method according to claim 3, characterized in that The step of respectively performing inverse Fourier transformation on the reference sub-K space data and each of the zero-filled sub-K space data to obtain a reconstructed image corresponding to each type of pre-imaging nuclide comprises: Performing the inverse Fourier transform on the reference sub-K space data to obtain a reference reconstructed image corresponding to the reference sub-K space data; and performing the inverse Fourier transform on each of the zero-filled sub-K space data to obtain a zero-filled reconstructed image corresponding to each of the zero-filled sub-K space data; According to the image size of the reference reconstructed image, the central area is extracted from each of the zero-filled reconstructed images as the central image; the reference reconstructed image and each of the central images are respectively used as the reconstructed images of the pre-imaging nuclides of the corresponding category.
5. The method according to claim 1, characterized in that By prepolarization, the longitudinal magnetization vector of each pre-imaging nuclide under extremely low field is increased, including: Applying a prepolarization magnetic field of a preset first duration to the imaging region in a direction parallel to the static magnetic field to increase the magnetization vector of each of the pre-imaging nuclides in the imaging region so that the magnetization vector is arranged along the magnetic field direction of the static magnetic field; or, A prepolarization magnetic field of a preset first duration is applied to the imaging area along a direction perpendicular to the static magnetic field, so that each of the pre-imaging nuclides generates a magnetization vector arranged along the magnetic field direction of the prepolarization magnetic field; within a preset second duration before the prepolarization magnetic field is turned off, an adiabatic pulse of a preset third duration is applied along a direction parallel to the static magnetic field, so that the magnetization vector of each of the pre-imaging nuclides is transferred from a magnetic field direction perpendicular to the static magnetic field to a magnetic field direction parallel to the static magnetic field.
6. The method according to claim 1, characterized in that The implementation of the spatial coding and signal acquisition includes: Before signal acquisition, a first gradient magnetic field is applied to the pre-imaging nuclides along the layer selection direction, and under the action of the first gradient magnetic field, a radio frequency pulse of a preset frequency and bandwidth is applied to each of the pre-imaging nuclides, and a nuclide layer formed by the pre-imaging nuclides excited by the radio frequency pulse is used as an imaging nuclide plane; and a second gradient magnetic field is applied to the imaging nuclide plane along the phase encoding direction, so that the pre-imaging nuclides at different positions in the phase encoding direction accumulate corresponding phases; During signal acquisition, a third gradient magnetic field is applied to the imaging nuclide plane along the frequency encoding direction so that the pre-imaging nuclide at different positions in the frequency encoding direction has a corresponding resonance frequency, so as to acquire a K-space signal corresponding to each of the pre-imaging nuclide in the imaging nuclide plane; the K-space signal reflects the position of the pre-imaging nuclide in the phase encoding direction and the frequency encoding direction.
7. The method according to claim 1, characterized in that The acquiring of total K space data corresponding to the K space signal set and zero-filling of the total K space data comprises: Perform K space filling on each of the K space signals in the K space signal set to obtain the total K space data corresponding to the K space signal set; perform zero filling on the total K space data according to a preset zero filling multiple to obtain the total K space data after zero filling.
8. An extremely low field multi-nuclear synchronous magnetic resonance imaging system, characterized in that: include: A signal acquisition module is used to improve the longitudinal magnetization vector of each pre-imaging nuclide under an extremely low field; perform spatial encoding and signal acquisition on each of the pre-imaging nuclides to obtain a K-space signal set corresponding to the imaging nuclide plane in the pre-imaging nuclide; a K-space data acquisition module is used to obtain the total K-space data corresponding to the K-space signal set, and fill the total K-space data with zeros; based on the total K-space data after zero filling, obtain the total frequency distribution corresponding to the imaging nuclide plane; split the total frequency distribution to obtain the sub-frequency distribution corresponding to each type of pre-imaging nuclide; based on each of the sub-frequency distributions, obtain the sub-K-space data corresponding to each type of pre-imaging nuclide; The synchronous imaging module is used to reconstruct images of various types of pre-imaging nuclides based on the sub-K space data to obtain reconstructed images corresponding to various types of pre-imaging nuclides.
9. A computer device, characterized in that: include: Memory for storing computer programs; A processor, configured to execute the computer program stored in the memory so as to enable the apparatus to perform the extremely low field multi-nuclear synchronous magnetic resonance imaging method according to any one of claims 1 to 7.
10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed, the extremely low field multi-nuclear synchronous magnetic resonance imaging method according to any one of claims 1 to 7 is implemented.