Longitudinal relaxation time weighted and susceptibility weighted imaging image acquisition method and apparatus

Abstract

The embodiment of the application discloses longitudinal relaxation time weighting and magnetic susceptibility weighted imaging image acquisition method and device. The method comprises the following steps: in the process of multiple excitation 3DEPI, for each excitation, first, radio frequency pulse excitation is carried out on the target tissue, and meanwhile, a selected layer gradient pulse is applied to the target tissue in the selected layer encoding direction; after the radio frequency pulse excitation and the selected layer gradient pulse are applied, when the preset T1W data acquisition time comes, T1W data is collected for the echo of excitation; after the T1W data acquisition is completed, when the preset SWI data acquisition time comes, SWI data is collected for the echo of excitation; image reconstruction is carried out on the T1W data collected in all excitation processes to obtain the T1W image of the target tissue; and image reconstruction is carried out on the SWI data collected in all excitation processes to obtain the SWI image of the target tissue. The embodiment of the application can simultaneously acquire T1W data and SWI data in one excitation process.

Description

Technical Field

[0001] This invention relates to the field of MRI (Magnetic Resonance Imaging) technology, including methods, devices, and MRI systems for acquiring T1W (T1-weighted) images and SWI (Susceptibility-weighted Imaging) images. Background Technology

[0002] MRI works by applying radio frequency (RF) pulses of a specific frequency to the human body in a static magnetic field, which excites hydrogen protons in the body to produce MR (Magnetic Resonance) phenomenon. After the pulse stops, the protons generate MR signals during relaxation. MR images are produced through the processing of MR signals, including reception, spatial encoding, and image reconstruction.

[0003] During imaging, after RF excitation, slice selection is first performed using the Z-axis gradient, selecting one slice for imaging. Next, the Y-axis gradient magnetic field is activated, causing different precession velocities of the magnetic moments at different Y positions. Then, the Y gradient is deactivated, restoring the magnetic moment velocities to the same level. However, due to the previous different precession velocities, the phase shifts at different Y positions differ; this process is called phase encoding. Next, the X-axis gradient is activated, resulting in different magnetic moment velocities at different X positions; this process is called frequency encoding. Thus, through phase encoding and frequency encoding, the locations of each slice in a 2D image can be determined. The signal acquired by the receiving coil is a k-space signal, which can be transformed into an image using Fourier transform. A new slice selection is then performed using the Z-axis gradient, and the above process is repeated to obtain MRI images of other slices.

[0004] Different RF sequences can be constructed by combining 90° RF and 180° RF. Commonly used MRI RF sequences include: SE (Spin-Echosequence), TSE (Turbo Spin-Echo sequence), GRE (Gradient-Echo sequence), and EPI (Echo Planar Imaging). GRE and EPI are both gradient echo sequences. Gradient echoes are generated by switching the readout direction (i.e., the X-axis) forward and reverse after a single RF excitation. EPI differs from typical gradient echoes in that it generates a gradient echo with each continuous forward and reverse switching of the readout gradient field after a single RF excitation, thus exhibiting an echo chain, similar to TSE.

[0005] In magnetic resonance imaging (MRI), stationary tissues accumulate zero phase after experiencing gradients of the same magnitude but opposite direction. However, for moving tissues such as flowing blood or cerebrospinal fluid, the phase accumulation is not zero. When subsequent encoding gradients are applied, the moving tissues that already have phase are incorrectly encoded and appear in other locations, becoming flow artifacts. Flow Compensation (FC), also called Gradient Moment Nulling (GMN), is a technique that uses specially designed gradient fields to reduce or eliminate flow artifacts. There are many gradient combination modes in FC. By transforming multiple positive and negative gradient fields of different areas, the phase shift of fluids at various velocities can eventually approach zero, thus eliminating motion artifacts. Generally, FC compensates for the effects of uniform flow by eliminating the first-order gradient moment.

[0006] Currently, low-field MRI scanners are widely used. The biggest feature of low-field MRI scanners is their low signal-to-noise ratio. However, the signal-to-noise ratio is proportional to the field strength of B0 (main magnetic field). This requires a longer MR measurement time, which reduces the throughput of MR measurements and the patient experience.

[0007] Brain imaging is very common in MRI scans. Typically, routine brain imaging requires T1W (T1-weighted) imaging, T2W (T2-weighted) imaging, T2 FLAIR (T2-fluid-attenuated inversion recovery) imaging, DWI (diffusion-weighted imaging), and SWI (susceptibility-weighted imaging). Currently, these imaging techniques require independent scanning procedures, typically taking a total of 10 to 20 minutes. Summary of the Invention

[0008] In view of this, the present invention provides, on the one hand, a method for acquiring T1W and SWI images, and on the other hand, a device and MRI system for acquiring T1W and SWI images, so as to acquire T1W images and SWI images simultaneously.

[0009] A method for acquiring longitudinal relaxation time-weighted (T1W) and magnetic susceptibility-weighted imaging (SWI) images includes:

[0010] In the process of multiple excitations of 3D echo planar imaging (EPI), for each excitation, the target tissue is first excited by a radio frequency pulse, and at the same time, a layer-selective gradient pulse is applied to the target tissue in the layer-selective encoding direction. After the radio frequency pulse excitation and the layer-selective gradient pulse application are completed, T1W data is acquired for the excitation echo when the preset T1W data acquisition time arrives. After the T1W data acquisition is completed, SWI data is acquired for the excitation echo when the preset SWI data acquisition time arrives.

[0011] Image reconstruction was performed on the T1W data acquired during all excitation processes to obtain T1W images of the target tissue; image reconstruction was also performed on the SWI data acquired during all excitation processes to obtain SWI images of the target tissue.

[0012] Prior to image reconstruction of the T1W data acquired during all excitation processes, the process further includes:

[0013] Radio frequency pulse excitation is performed on the target tissue, and a layer selection gradient pulse is applied to the target tissue in the layer selection coding direction. After the radio frequency pulse excitation and layer selection gradient pulse application are completed, T1W phase correction data is acquired when the preset T1W phase correction data acquisition time arrives. After the T1W phase correction data acquisition is completed, SWI phase correction data is acquired when the preset SWI phase correction data acquisition time arrives.

[0014] The image reconstruction of T1W data acquired during all excitation processes includes:

[0015] The T1W phase correction data was used to perform phase correction on the T1W data acquired during all excitation processes, and the phase-corrected T1W data was used for image reconstruction.

[0016] The image reconstruction of SWI data acquired during all excitation processes includes:

[0017] SWI phase correction data was used to perform phase correction on the SWI data acquired during all excitation processes, and the phase-corrected SWI data was used for image reconstruction.

[0018] The T1W data acquired for the excitation echo includes:

[0019] Gradient pulses with a cumulative zero-order moment are applied to the target tissue in both the phase encoding direction and the layer selection encoding direction.

[0020] The T1W data acquired for the excitation echo includes:

[0021] T1W data is acquired using the EPI acquisition method for the excited echo; or,

[0022] T1W data were acquired using a spiral SPIRAL acquisition method to target the excited echo.

[0023] After the T1W data acquisition is completed, and before the preset SWI data acquisition time arrives, the process further includes:

[0024] First-order moment flow compensation is performed on the readout direction, phase encoding direction, and layer-selective encoding direction of the excited echo.

[0025] The first-order moment flow compensation for the readout direction of the excited echo includes:

[0026] The first-order moment flow compensation in the readout direction is performed using the following formula:

[0027]

[0028] Where, m 1,r The first moment that needs to be compensated for in the readout direction of the excited echo; m 0,r-prephase The zeroth moment of the T1W pre-divergent gradient pulse in the readout direction; Δt r-prephase m is the time interval between the center of the T1W pre-phase gradient pulse in the readout direction and the echo center of the SWI data acquisition; 0,n The zero-order moment of the nth T1W readout gradient pulse, where N is the number of T1W readout gradient pulses; Δt n m is the time interval between the center of the gradient pulse read from the nth T1W and the center of the echo acquired by the SWI data; 0,m Let M be the zero-order moment of the m-th SWI readout gradient pulse, and M be the number of SWI readout gradient pulses; Δt m M is the time interval between the center of the m-th SWI readout gradient pulse and the center of the SWI data acquisition echo. center = (M-1) / 2.

[0029] The first-order moment flow compensation for the phase encoding direction of the excited echo includes:

[0030] The first-order moment flow compensation in the phase encoding direction of the excited echo is performed using the following formula:

[0031]

[0032] Where, m 1,p This is to compensate for the first moment in the phase encoding direction of the excited echo; m 0,p-prephase1 The zeroth moment of the pre-dephasing gradient pulse in the phase encoding direction; Δt p-prephase1 m is the time interval between the center of the pre-dephasing gradient pulse in the phase encoding direction and the echo center of the SWI data acquisition; 0,p-rewinder1The zeroth moment of the phase convergence gradient pulse in the phase encoding direction; Δt p-rewinder1 m is the time interval between the center of the phase convergence gradient pulse in the phase encoding direction and the echo center of the SWI data acquisition; 0,n The zeroth moment of the nth T1W phase-coded gradient pulse; Δt n The time interval between the center of the nth T1W phase-coded gradient pulse and the echo center of the SWI data acquisition; N-1 is the number of T1W phase-coded gradient pulses; m 0,m The zeroth moment of the m-th SWI phase-coded gradient pulse; Δt m M is the time interval between the center of the m-th SWI phase-coded gradient pulse and the echo center of the SWI data acquisition. center =M / 2, where M is the number of SWI phase-coded gradient pulses.

[0033] The first-order moment flow compensation for the selected coding direction of the excited echo includes:

[0034] The first-order moment flow compensation for the excitation echo in the layer-selective coding direction is performed using the following formula:

[0035] m 1,s =m 0,s-encoding1 ·Δt s-encoding1 +m 0,s-rewinder1 ·Δt s-rewinder1 +m 0,s-encoding2 ·Δt s-encoding2

[0036] Where, m 1,s This is the first moment that needs to be compensated for in the layer-selective coding direction of the excited echo; m 0,s-encoding1 The zeroth moment of the gradient pulse encoded for the T1W block; Δt s-encoding1 m is the time interval between the center of the T1W block-coded gradient pulse and the echo center of the SWI data acquisition; 0,s-rewinder1 The zeroth moment of the phase-converging gradient pulse in the layer-selective coding direction; Δt s-rewinder1 m is the time interval between the center of the phase convergence gradient pulse in the layer selection coding direction and the echo center of the SWI data acquisition; 0,s-encoding2 Encode the zeroth moment of the gradient pulse for the SWI block; Δt s-encoding2 The time interval between the center of the SWI block-coded gradient pulse and the echo center of the SWI data acquisition.

[0037] A longitudinal relaxation time-weighted (T1W) and magnetic susceptibility-weighted imaging (SWI) image acquisition device includes:

[0038] The data acquisition module is used in the process of 3D echo planar imaging EPI with multiple excitations. For each excitation, the target tissue is first excited by radio frequency pulse, and at the same time, a layer-selective gradient pulse is applied to the target tissue in the layer-selective encoding direction. After the radio frequency pulse excitation and the layer-selective gradient pulse are applied, T1W data is acquired for the excitation echo when the preset T1W data acquisition time arrives. After the T1W data acquisition is completed, SWI data is acquired for the excitation echo when the preset SWI data acquisition time arrives.

[0039] The image reconstruction module is used to reconstruct images of T1W data acquired during all excitation processes to obtain T1W images of the target tissue; and to reconstruct images of SWI data acquired during all excitation processes to obtain SWI images of the target tissue.

[0040] A magnetic resonance imaging system includes the longitudinal relaxation time-weighted (T1W) and magnetic susceptibility-weighted imaging (SWI) image acquisition device as described above.

[0041] In this embodiment of the invention, T1W data is acquired during the waiting period for SWI data acquisition after radiofrequency excitation during a single excitation process. This allows for the simultaneous acquisition of both T1W and SWI data during a single excitation process, accelerating the acquisition of T1W and SWI images, reducing MRI scanning time, and facilitating its application in low-field MRI scanners. Attached Figure Description

[0042] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which will make the above and other features and advantages of the present invention more apparent to those skilled in the art. In the drawings:

[0043] Figure 1 This is a flowchart of the T1W and SWI image acquisition method provided in the first embodiment of the present invention;

[0044] Figure 2 This is a schematic diagram of the sequence used in a single excitation process when acquiring T1W and SWI images in an application example of the present invention;

[0045] Figure 3 This is a schematic diagram of the structure of the T1W and SWI image acquisition device provided in an embodiment of the present invention.

[0046] The accompanying figure is labeled as follows:

[0047]

[0048] Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the present invention clearer, the following embodiments are provided to further illustrate the present invention in detail.

[0050] Because T1W imaging provides excellent contrast for depicting gray matter (GM) and white matter (WM), it is essential for brain MRI examinations. Currently, two-dimensional spin echo or gradient echo sequences are commonly used for brain T1W imaging, and there is also evidence that using 3D EPI can accelerate the acquisition of brain T1W data.

[0051] SWI can provide enhanced image contrast for tissues with varying sensitivities. The standard technique for acquiring SWI images is the full flow compensated 3D-GRE (Gradient Echo) sequence, which typically requires a long scan time.

[0052] This invention provides a method for simultaneously acquiring T1W and SWI data during a single excitation process, thereby accelerating the acquisition of T1W and SWI images, reducing MRI scan time, and facilitating its application in low-field MRI scanners.

[0053] Figure 1 The flowchart of the T1W and SWI image acquisition method provided in the first embodiment of the present invention is as follows:

[0054] Step 101: In the process of multiple excitations of 3D (three-dimensional) EPI, for each excitation, the target tissue is first excited by radio frequency pulse, and at the same time, a layer-selective gradient pulse is applied to the target tissue in the layer-selective encoding direction. After the radio frequency pulse excitation and the layer-selective gradient pulse are applied, when the preset T1W data acquisition time arrives, T1W data is acquired based on the excitation echo. After the T1W data acquisition is completed, when the preset SWI data acquisition time arrives, SWI data is acquired based on the excitation echo.

[0055] Since the embodiments of the present invention are aimed at 3D EPI, the "layer selection" mentioned in the embodiments of the present invention refers to the layer selection in 3D magnetic resonance imaging. Here, "layer" has thickness and can be understood as "block".

[0056] Step 102: Reconstruct images from the T1W data acquired during all excitation processes to obtain T1W images of the target tissue; reconstruct images from the SWI data acquired during all excitation processes to obtain SWI images of the target tissue.

[0057] In the above embodiments, by acquiring T1W data during the SWI data acquisition time after radiofrequency excitation in one excitation process, both T1W and SWI data are acquired simultaneously in one excitation process, which speeds up the acquisition of T1W and SWI images, reduces MRI scanning time, and is convenient for application in low-field MRI scanners.

[0058] In one optional embodiment, before step 102, the method further includes: exciting the target tissue with a radio frequency pulse, and simultaneously applying a layer-selective gradient pulse to the target tissue in the layer-selective coding direction; after the radio frequency pulse excitation and the layer-selective gradient pulse application are completed, when the preset T1W phase correction data acquisition time arrives, T1W phase correction data is acquired; after the T1W phase correction data acquisition is completed, when the preset SWI phase correction data acquisition time arrives, SWI phase correction data is acquired.

[0059] In step 102, image reconstruction is performed on the T1W data collected during all excitation processes, including: using T1W phase correction data to perform phase correction on the T1W data collected during all excitation processes, and using all phase-corrected T1W data to perform image reconstruction.

[0060] Image reconstruction is performed on the SWI data acquired during all excitation processes, including: performing phase correction on the SWI data acquired during all excitation processes using SWI phase correction data, and performing image reconstruction on all phase-corrected SWI data.

[0061] Through the above embodiments, phase correction was performed on the acquired T1W and SWI data, thereby improving the quality of the reconstructed image.

[0062] In one optional embodiment, step 101, acquiring T1W data for the excitation echo, includes: applying gradient pulses with a cumulative zero-order moment to the target tissue in the phase encoding direction and the layer selection encoding direction, respectively.

[0063] In one optional embodiment, step 101, acquiring T1W data for the excitation echo, includes: acquiring T1W data for the excitation echo using the EPI acquisition method; or, acquiring T1W data for the excitation echo using the SPIRAL acquisition method.

[0064] In one optional embodiment, step 101, after the T1W data acquisition is completed and before the preset SWI data acquisition time arrives, further includes: performing first-order moment flow compensation for the readout direction, phase encoding direction, and layer selection encoding direction of the excited echo.

[0065] In one optional embodiment, step 101, performing first-order moment flow compensation in the selected layer direction for the excited echo, includes:

[0066] The first-order moment flow compensation in the readout direction is performed using the following formula:

[0067]

[0068] Where, m 1,r The first moment that needs to be compensated for in the readout direction of the excited echo; m 0,r-prephase The T1W pre-dispersive gradient pulse in the readout direction (denoted as G) r-prephase The zeroth moment of Δt; r-prephase To from G r-prephase The time interval between the center of the SWI data acquisition and the echo center (denoted as TEswi); m 0,n Read out the gradient pulse for the nth T1W (let's call it G). r1-n The zeroth moment of Δt; n To from G r1-n The time interval between the center and TEswi; N is the number of T1W readout gradient pulses; m 0,m For the m-th SWI readout gradient pulse (let G be the gradient pulse), r2-m The zeroth moment of Δt; m To from G r2-m The time interval between the center and TEswi, M center = (M-1) / 2, where M is the number of gradient pulses read out by SWI.

[0069] In one optional embodiment, in step 101, first-order moment flow compensation in the phase encoding direction is performed on the excited echo:

[0070] The first-order moment flow compensation in the phase encoding direction of the excited echo is performed using the following formula:

[0071]

[0072] Where, m 1,p This is to compensate for the first moment in the phase encoding direction of the excited echo; m 0,p-prephase1 The pre-dephasing gradient pulse in the phase encoding direction (denoted as G) p-prephase1 The zeroth moment of Δt; p-prephase1 To from G p-prephase1 The time interval between the center of the SWI data acquisition and the echo center (denoted as TEswi); m 0,p-rewinder1 The phase convergence gradient pulse in the phase encoding direction (denoted as G) p-rewinder1 The zeroth moment of Δt; p-rewinder1 To from G p-rewinder1 The time interval between the center and TEswi; m 0,n The nth T1W phase-coded gradient pulse (denoted as G)p-blip1-n The zeroth moment of Δt; n To from G p-blip1-n The time interval between the center and TEswi; N-1 is the number of T1W phase-coded gradient pulses; m 0,m For the m-th SWI phase-coded gradient pulse (let G be the gradient pulse), p-blip2-m The zeroth moment of Δt; m To from G p-blip2-m The time interval between the center and TEswi, M center =M / 2, where M is the number of SWI phase-coded gradient pulses.

[0073] In one optional embodiment, in step 101, first-order moment flow compensation is performed in the layer-selective coding direction for the excited echo:

[0074] The first-order moment flow compensation for the excitation echo in the layer-selective coding direction is performed using the following formula:

[0075] m 1,s =m 0,s-encoding1 ·Δt s-encoding1 +m 0,s-rewinder1 ·Δt s-rewinder1 +m 0,s-encoding2 ·Δt s-encoding2

[0076] Where, m 1,s To compensate for the first-order moment flow gradient that needs to be compensated in the selected coding direction for the excited echo; m 0,s-encoding1 Encode gradient pulses for T1W block (let's call them G) s-encoding1 The zeroth moment of Δt; s-encoding1 To from G s-encoding1 The time interval between the center of the SWI data acquisition and the echo center (denoted as TEswi); m 0,s-rewinder1 The phase-regrouping gradient pulse (denoted as G) in the layer-selection coding direction s-rewinder1 The zeroth moment of Δt; s-rewinder1 To from G s-rewinder1 The time interval between the center and TEswi; m 0,s-encoding2 Encode gradient pulses for SWI blocks (let G be the code). s-encoding2 The zeroth moment of Δt; s-encoding2 To from G s-encoding2 The time interval between the center and TEswi.

[0077] The first-order moment flow compensation method described above for reading out the echo, phase encoding direction, and layer selection encoding direction is particularly suitable for scenarios where T1W data is acquired using EPI acquisition.

[0078] Through the above embodiments, first-order moment flow compensation was performed on the excited echo in the readout direction, phase encoding direction, and layer selection encoding direction, thereby eliminating arterial signal contamination in SWI images and improving SWI image quality.

[0079] Figure 2 This is a schematic diagram of the sequence used in a single excitation process when acquiring T1W and SWI images in an application example of the present invention;

[0080] Wherein, RF is a block-selective excitation pulse emitted to the target tissue;

[0081] Gread is the gradient field applied to the target tissue in the readout direction, where 2221 is the pre-dephased gradient pulse in the readout direction (denoted as G). r-prephase ), 2222-2226 are the gradient pulses read out by T1W (let's call them G). r1-n , n is the pulse number of the T1W readout gradient pulse (n = 0, 1, 2, 3, 4), 2231-2232 are the flow compensation gradient pulses in the readout direction, and 2241-2245 are the SWI readout gradient pulses (let's say G). r2-m m is the pulse number of the gradient pulse readout by SWI (m = 0, 1, 2, 3, 4); 20 is the echo center of SWI data acquisition (set as TEswi); in this example, the total number N of gradient pulses readout by T1W is 5, and the total number M of gradient pulses readout by SWI is 5.

[0082] Gphase represents the gradient field applied to the target tissue in the phase encoding direction, where 2321 is the T1W pre-dephasing gradient pulse in the phase encoding direction (denoted as G). p-prephase1 ), 2322-2325 are T1W phase-coded gradient pulses (denoted as G). p-blip1-n , where n is the pulse number of the phase-encoded gradient pulse (n = 0, 1, 2, 3), and 2326 is the phase convergence gradient pulse in the phase-encoded direction (denoted as G). p-rewinder1 ), 2331-2332 are the flow compensation gradient pulses in the phase encoding direction, and 2341 is the SWI pre-dephasing gradient pulse in the phase encoding direction (let's call it G). p-prephase2 ), 2342-2345 are SWI phase-coded gradient pulses (denoted as G). p-blip2-m , m is the pulse number of the SWI phase-coded gradient pulse, m = 0, 1, 2, 3); in this example, the total number of T1W phase-coded gradient pulses is N-1 = 4, and the total number of SWI phase-coded gradient pulses is M = 4.

[0083] Gslice is the gradient field applied to the target tissue in the layer-selective coding direction, where 2411-2413 are layer-selective gradient pulses; 2421 is the T1W block coding gradient pulse (denoted as G). s-encoding1), 2422 is the phase convergence gradient pulse in the layer selection coding direction (let's call it G). s-rewinder1 ), 2431-2432 are flow compensation gradient pulses in the selected layer coding direction, and 2441 is the SWI block coding gradient pulse.

[0084] Figure 3 This is a schematic diagram of the structure of the T1W and SWI image acquisition device 30 provided in an embodiment of the present invention. The device mainly includes:

[0085] The data acquisition module 31 is used in the process of multiple excitations of 3D EPI to first excite the target tissue with radio frequency pulses for each excitation, and at the same time apply layer-selective gradient pulses to the target tissue in the layer-selective encoding direction. After the radio frequency pulse excitation and layer-selective gradient pulse application are completed, T1W data is acquired based on the excitation echo when the preset T1W data acquisition time arrives. After the T1W data acquisition is completed, SWI data is acquired based on the excitation echo when the preset SWI data acquisition time arrives.

[0086] The image reconstruction module 32 is used to reconstruct images of T1W data acquired during all excitation processes to obtain T1W images of the target tissue; and to reconstruct images of SWI data acquired during all excitation processes to obtain SWI images of the target tissue.

[0087] In an optional embodiment, the data acquisition module 31 is further configured to: excite the target tissue with a radio frequency pulse, and simultaneously apply a layer selection gradient pulse to the target tissue in the layer selection coding direction; after the radio frequency pulse excitation and the layer selection gradient pulse application are completed, acquire T1W phase correction data when the preset T1W phase correction data acquisition time arrives; after the T1W phase correction data acquisition is completed, acquire SWI phase correction data when the preset SWI phase correction data acquisition time arrives.

[0088] The image reconstruction module 32 performs image reconstruction on the T1W data acquired during all excitation processes, including: performing phase correction on the T1W data acquired during all excitation processes using T1W phase correction data, and performing image reconstruction on all phase-corrected T1W data.

[0089] The image reconstruction module 32 performs image reconstruction on the SWI data acquired during all excitation processes, including: performing phase correction on the SWI data acquired during all excitation processes using SWI phase correction data, and performing image reconstruction on all phase-corrected SWI data.

[0090] In one optional embodiment, the data acquisition module 31 acquires T1W data for the excited echo, including: applying gradient pulses with a cumulative zero-order moment to the target tissue in the phase encoding direction and the layer selection encoding direction, respectively.

[0091] In one optional embodiment, the data acquisition module 31 acquires T1W data for the excited echo by: acquiring T1W data for the excited echo using the EPI acquisition method; or, acquiring T1W data for the excited echo using the SPIRAL acquisition method.

[0092] In one optional embodiment, after the T1W data acquisition is completed and before the preset SWI data acquisition time arrives, the data acquisition module 31 is further used to: perform first-order moment flow compensation for the readout direction, phase encoding direction and layer selection encoding direction of the excited echo.

[0093] In one optional embodiment, the data acquisition module 31 performs first-order moment flow compensation in the readout direction for the excited echo, including:

[0094] The first-order moment flow compensation in the readout direction is performed using the following formula:

[0095]

[0096] Where, m 1,r The first moment that needs to be compensated for in the readout direction of the excited echo; m 0,r-prephase The zero-order moment of the T1W pre-divergent gradient pulse in the readout direction; Δt r-prephase m is the time interval between the center of the T1W pre-phase gradient pulse in the readout direction and the echo center of the SWI data acquisition; 0,n The zero-order moment of the nth T1W readout gradient pulse, where N is the number of T1W readout gradient pulses; Δt n m is the time interval between the center of the gradient pulse read from the nth T1W and the center of the echo acquired by the SWI data; 0,m Let M be the zero-order moment of the m-th SWI readout gradient pulse, and M be the number of SWI readout gradient pulses; Δt m M is the time interval between the center of the m-th SWI readout gradient pulse and the center of the SWI data acquisition echo. center = (M-1) / 2.

[0097] In one optional embodiment, the data acquisition module 31 performs first-order moment flow compensation in the phase encoding direction for the excited echo, including:

[0098] The first-order moment flow compensation in the phase encoding direction of the excited echo is performed using the following formula:

[0099]

[0100] Where, m 1,p This is to compensate for the first moment in the phase encoding direction of the excited echo; m 0,p-prephase1The zeroth moment of the pre-dephasing gradient pulse in the phase encoding direction; Δt p-prephase1 m is the time interval between the center of the pre-dephasing gradient pulse in the phase encoding direction and the echo center of the SWI data acquisition; 0,p-rewinder1 The zeroth moment of the phase convergence gradient pulse in the phase encoding direction; Δt p-rewinder1 m is the time interval between the center of the phase convergence gradient pulse in the phase encoding direction and the echo center of the SWI data acquisition; 0,n The zeroth moment of the nth T1W phase-coded gradient pulse; Δt n N is the time interval between the center of the nth T1W phase-coded gradient pulse and the echo center of the SWI data acquisition; N-1 is the number of T1W phase-coded gradient pulses; m 0,m The zeroth moment of the m-th SWI phase-coded gradient pulse; Δt m M is the time interval between the center of the m-th SWI phase-coded gradient pulse and the echo center of the SWI data acquisition. center =M / 2, where M is the number of SWI phase-coded gradient pulses.

[0101] In one optional embodiment, the data acquisition module 31 performs first-order moment flow compensation in the layer-selective encoding direction for the excited echo, including:

[0102] The first-order moment flow compensation for the excitation echo in the layer-selective coding direction is performed using the following formula:

[0103] m 1,s =m 0,s-encoding1 ·Δt s-encoding1 +m 0,s-rewinder1 ·Δt s-rewinder1 +m 0,s-encoding2 ·Δt s-encoding2

[0104] Where, m 1,s This is the first moment that needs to be compensated for in the layer-selective coding direction of the excited echo; m 0,s-encoding1 The zeroth moment of the gradient pulse encoded for the T1W block; Δt s-encoding1 m is the time interval between the center of the T1W block-coded gradient pulse and the echo center of the SWI data acquisition; 0,s-rewinder1 The zeroth moment of the phase-converging gradient pulse in the layer-selective coding direction; Δt s-rewinder1 m is the time interval between the center of the phase convergence gradient pulse in the layer selection coding direction and the echo center of the SWI data acquisition; 0,s-encoding2 Encode the zeroth moment of the gradient pulse for the SWI block; Δt s-encoding2 The time interval between the center of the SWI block-coded gradient pulse and the echo center of the SWI data acquisition.

[0105] The magnetic resonance imaging system proposed in this embodiment of the invention may include the T1W image and SWI image acquisition device (30) provided in any of the above embodiments.

[0106] In this embodiment of the invention, the geometric parameters of T1W data acquisition and SWI data acquisition, such as the size of the image matrix and FOV (Field of View), can be the same or different.

[0107] The embodiments of the present invention can be applied to brain MRI.

[0108] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for acquiring longitudinal relaxation time-weighted (T1W) and magnetic susceptibility-weighted imaging (SWI) images, characterized in that, include: In the process of multiple excitations of 3D echo planar imaging (EPI), for each excitation, the target tissue is first excited by a radio frequency pulse, and at the same time, a layer-selective gradient pulse is applied to the target tissue in the layer-selective encoding direction. After the radio frequency pulse excitation and the layer-selective gradient pulse application are completed, T1W data is acquired for the excitation echo when the preset T1W data acquisition time arrives. After the T1W data acquisition is completed, SWI data is acquired for the excitation echo when the preset SWI data acquisition time arrives. Image reconstruction was performed on the T1W data acquired during all excitation processes to obtain T1W images of the target tissue; image reconstruction was also performed on the SWI data acquired during all excitation processes to obtain SWI images of the target tissue.

2. The method according to claim 1, characterized in that, Prior to image reconstruction of the T1W data acquired during all excitation processes, the process further includes: Radio frequency pulse excitation is performed on the target tissue, and a layer selection gradient pulse is applied to the target tissue in the layer selection coding direction. After the radio frequency pulse excitation and layer selection gradient pulse application are completed, T1W phase correction data is acquired when the preset T1W phase correction data acquisition time arrives. After the T1W phase correction data acquisition is completed, SWI phase correction data is acquired when the preset SWI phase correction data acquisition time arrives. The image reconstruction of T1W data acquired during all excitation processes includes: The T1W phase correction data was used to perform phase correction on the T1W data acquired during all excitation processes, and the phase-corrected T1W data was used for image reconstruction. The image reconstruction of SWI data acquired during all excitation processes includes: SWI phase correction data was used to perform phase correction on the SWI data acquired during all excitation processes, and the phase-corrected SWI data was used for image reconstruction.

3. The method according to claim 1, characterized in that, The T1W data acquired for the excitation echo includes: Gradient pulses with a cumulative zero-order moment are applied to the target tissue in both the phase encoding direction and the layer selection encoding direction.

4. The method according to claim 1, characterized in that, The T1W data acquired for the excitation echo includes: T1W data is acquired using the EPI acquisition method for the excited echo; or, T1W data were acquired using a spiral SPIRAL acquisition method to target the excited echo.

5. The method according to claim 1, characterized in that, After the T1W data acquisition is completed, and before the preset SWI data acquisition time arrives, the process further includes: First-order moment flow compensation is performed on the readout direction, phase encoding direction, and layer-selective encoding direction of the excited echo.

6. The method according to claim 5, characterized in that, The first-order moment flow compensation for the readout direction of the excited echo includes: The first-order moment flow compensation in the readout direction is performed using the following formula: Where, m 1,r The first moment that needs to be compensated for in the readout direction of the excited echo; m 0,r-prephase The zeroth moment of the T1W pre-divergent gradient pulse in the readout direction; Δt r-prephase m is the time interval between the center of the T1W pre-phase gradient pulse in the readout direction and the echo center of the SWI data acquisition; 0,n The zero-order moment of the nth T1W readout gradient pulse, where N is the number of T1W readout gradient pulses; Δt n m is the time interval between the center of the gradient pulse read from the nth T1W and the center of the echo acquired by the SWI data; 0,m Let M be the zero-order moment of the m-th SWI readout gradient pulse, and M be the number of SWI readout gradient pulses; Δt m M is the time interval between the center of the m-th SWI readout gradient pulse and the center of the SWI data acquisition echo. center = (M-1) / 2.

7. The method according to claim 5, characterized in that, The first-order moment flow compensation for the phase encoding direction of the excited echo includes: The first-order moment flow compensation in the phase encoding direction of the excited echo is performed using the following formula: Where, m 1,p This is to compensate for the first moment in the phase encoding direction of the excited echo; m 0,p-prephase1 The zeroth moment of the pre-dephasing gradient pulse in the phase encoding direction; Δt p-prephase1 m is the time interval between the center of the pre-dephasing gradient pulse in the phase encoding direction and the echo center of the SWI data acquisition; 0,p-rewinder1 The zeroth moment of the phase convergence gradient pulse in the phase encoding direction; Δt p-rewinder1 m is the time interval between the center of the phase convergence gradient pulse in the phase encoding direction and the echo center of the SWI data acquisition; 0,n The zeroth moment of the nth T1W phase-coded gradient pulse; Δt n The time interval between the center of the nth T1W phase-coded gradient pulse and the echo center of the SWI data acquisition; N-1 is the number of T1W phase-coded gradient pulses; m 0,m The zeroth moment of the m-th SWI phase-coded gradient pulse; Δt m M is the time interval between the center of the m-th SWI phase-coded gradient pulse and the echo center of the SWI data acquisition. center =M / 2, where M is the number of SWI phase-coded gradient pulses.

8. The method according to claim 5, characterized in that, The first-order moment flow compensation for the selected coding direction of the excited echo includes: The first-order moment flow compensation for the excitation echo in the layer-selective coding direction is performed using the following formula: m 1,s =m 0,s-encoding1 ·Δt s-encoding1 +m 0,s-rewinder1 ·Δt s-rewinder1 +m 0,s-encoding2 ·Δt s-encoding2 Where, m 1,s This is the first moment that needs to be compensated for in the layer-selective coding direction of the excited echo; m 0,s-encoding1 The zeroth moment of the gradient pulse encoded for the T1W block; Δt s-encoding1 m is the time interval between the center of the T1W block-coded gradient pulse and the echo center of the SWI data acquisition; 0,s-rewinder1 The zeroth moment of the phase-converging gradient pulse in the layer-selective coding direction; Δt s-rewinder1 m is the time interval between the center of the phase convergence gradient pulse in the layer selection coding direction and the echo center of the SWI data acquisition; 0,s-encoding2 Encode the zeroth moment of the gradient pulse for the SWI block; Δt s-encoding2 The time interval between the center of the SWI block-coded gradient pulse and the echo center of the SWI data acquisition.

9. A longitudinal relaxation time-weighted (T1W) and magnetic susceptibility-weighted imaging (SWI) image acquisition device (30), characterized in that, include: The data acquisition module (31) is used to, in the process of multiple excitations of 3D echo plane imaging EPI, first excite the target tissue with radio frequency pulses, and at the same time apply layer selection gradient pulses to the target tissue in the layer selection coding direction. After the radio frequency pulse excitation and layer selection gradient pulse application are completed, when the preset T1W data acquisition time arrives, T1W data is acquired for the excitation echo. After the T1W data acquisition is completed, when the preset SWI data acquisition time arrives, SWI data is acquired for the excitation echo. The image reconstruction module (32) is used to reconstruct the T1W data acquired during all excitation processes to obtain the T1W image of the target tissue; and to reconstruct the SWI data acquired during all excitation processes to obtain the SWI image of the target tissue.

10. A magnetic resonance imaging system, characterized in that, Includes the longitudinal relaxation time-weighted T1W and magnetic susceptibility-weighted imaging SWI image acquisition device (30) as described in claim 9.

Images