Image generation method, apparatus, device, and medium

Abstract

The application discloses an image generation method, device, equipment and medium, and relates to the technical field of magnetic resonance imaging. The image generation method comprises the following steps: performing air scanning processing based on a phase perturbation gradient echo sequence, and establishing a first steady state and a second steady state, wherein the phase perturbation gradient echo sequence is alternately excited based on a first flip angle and a second flip angle, the first steady state represents a steady state corresponding to the first flip angle, and the second steady state represents a steady state corresponding to the second flip angle; performing scanning processing based on the phase perturbation gradient echo sequence, acquiring a first echo signal corresponding to a first echo time in the first steady state, and acquiring a second echo signal corresponding to a second echo time in the second steady state; and performing data reconstruction based on the first echo signal, the first echo time, the second echo signal, the second echo time, the first flip angle and the second flip angle, to generate a target image.

Description

Technical Field

[0001] This application relates to the technical fields of magnetic resonance imaging, and in particular to an image generation method, apparatus, device and medium. Background Technology

[0002] Magnetic resonance imaging (MRI) has become an indispensable tool in clinical diagnosis and basic research due to its advantages such as no ionizing radiation, high soft tissue resolution, multi-planar imaging, and multi-contrast imaging. With the development of precision medicine, traditional imaging methods that primarily rely on single-weighted images (such as...) are becoming increasingly important. Weighted or The qualitative diagnostic model, based on weighted averages, has gradually shifted towards quantitative imaging. Magnetic resonance imaging (MRI) multiparameter imaging technology has emerged to meet this need, enabling the simultaneous acquisition of multiple physical and physiological parameters of tissues in a single scan, such as longitudinal relaxation time. ), lateral relaxation time ( These quantitative parameters, such as proton density (PD), apparent diffusion coefficient (ADC), and magnetic susceptibility, eliminate the influence of equipment and scanning protocols, and can more objectively and accurately reflect the pathophysiological information of tissues, such as microstructure, cell density, and metabolic state. This provides richer imaging biomarkers for early disease diagnosis, differentiation between benign and malignant diseases, and efficacy evaluation.

[0003] The conventional method for obtaining the aforementioned multiple parameters mainly involves performing multiple independent scans. For example, first performing a multi-echo spin echo sequence scan to obtain... map, then perform a reverse recovery sequence scan to obtain The process may require diffusion-weighted imaging (DWI) scans to obtain the ADC map, but this "step-by-step acquisition" mode has significant drawbacks, such as long scan times, difficulties in image spatial registration, and inconsistent scan parameters. Another related technology is imaging techniques that can simultaneously generate multiple parametric maps in a single acquisition, such as magnetic resonance fingerprinting (MRF), synthetic magnetic resonance imaging based on multiple inversion / multi-echo sequences (e.g., MAGiC), STAGE technology based on variable inversion angle / multi-echo sequences, and MTP technology based on variable inversion angle / multi-echo / dual TR (Repetition Time). These technologies significantly improve imaging efficiency and tissue quantification capabilities through specialized acquisition strategies and reconstruction methods. However, such simultaneous multi-parameter imaging methods still have one or more technical bottlenecks, such as reconstruction accuracy and robustness issues, parameter coupling and error propagation, and sensitivity to motion. Summary of the Invention

[0004] The embodiments of this application aim to at least partially solve one of the technical problems in the related art. Therefore, the purpose of the embodiments of this application is to provide an image generation method, apparatus, device, and medium that improves the efficiency and accuracy of image generation.

[0005] This application provides an image generation method, comprising: performing a blank scan based on a perturbed gradient echo sequence to establish a first steady state and a second steady state, wherein the perturbed gradient echo sequence is alternately excited based on a first flip angle and a second flip angle, the first steady state represents the steady state corresponding to the first flip angle, and the second steady state represents the steady state corresponding to the second flip angle; performing a scan based on the perturbed gradient echo sequence to obtain a first echo signal corresponding to a first echo time in the first steady state, and obtaining a second echo signal corresponding to a second echo time in the second steady state; and performing data reconstruction based on the first echo signal, the first echo time, the second echo signal, the second echo time, the first flip angle, and the second flip angle to generate a target image.

[0006] For example, the scrambled gradient echo sequence includes multiple sequence repetition times, the first echo time includes multiple times, and the second echo time includes multiple times. Scanning processing is performed based on the scrambled gradient echo sequence to obtain the first echo signal corresponding to the first echo time in a first steady state, and to obtain the second echo signal corresponding to the second echo time in a second steady state. This includes: within one sequence repetition time, performing radio frequency pulse excitation based on a first flip angle, and obtaining the corresponding first echo as the first echo signal at each first echo time; within the next sequence repetition time, performing radio frequency pulse excitation based on a second flip angle, and obtaining the corresponding second echo as the second echo signal at each second echo time, wherein, within multiple sequence repetition time periods, radio frequency pulse excitation corresponding to the first flip angle and the second flip angle are alternately performed.

[0007] For example, acquiring the corresponding first echo as the first echo signal at each first echo time includes: before each first echo time, performing flow velocity compensation gradient processing on the acquired previous first echo to obtain the processed first echo, wherein the processed first echo includes a bright blood signal; and using the processed first echo as the first echo signal.

[0008] For example, acquiring the corresponding second echo as the second echo signal at each second echo time includes: performing flow velocity compensation gradient processing on the acquired previous second echo before each second echo time except the last second echo time to obtain a processed second echo, wherein the processed second echo includes a bright blood signal; performing flow velocity encoding gradient processing on the processed second echo before the last second echo time to obtain an encoded second echo, wherein the encoded second echo includes a dark blood signal; and using the processed second echo and the encoded second echo as the second echo signal.

[0009] For example, the target image includes a quantitative map, which includes at least one of a longitudinal relaxation time map, a transverse relaxation time map, a proton density map, and a quantitative magnetic susceptibility imaging map; data reconstruction is performed based on a first echo signal, a first echo time, a second echo signal, a second echo time, a first flip angle, and a second flip angle to generate the target image, including: obtaining a longitudinal relaxation time map based on the first echo signal, the first echo time, the second echo signal, the second echo time, the first flip angle, and the second flip angle; and performing fitting processing based on the first echo signal and the first echo time to obtain a transverse relaxation time map, or performing fitting processing based on the second echo signal and the second echo time to obtain a transverse relaxation time map. A transverse relaxation time map is generated. Based on the longitudinal relaxation time map, the transverse relaxation time map, the first echo signal, the first echo time, the first flip angle, and the second flip angle, the initial magnetization vector intensity is determined. Based on the initial magnetization vector intensity, a proton density map is obtained. Alternatively, based on the longitudinal relaxation time map, the transverse relaxation time map, the second echo signal, the second echo time, the first flip angle, and the second flip angle, the initial magnetization vector intensity is determined. Based on the initial magnetization vector intensity, a proton density map is obtained. A quantitative magnetic susceptibility imaging map is obtained based on the amplitude signal and phase signal corresponding to the first echo signal. Alternatively, a quantitative magnetic susceptibility imaging map is obtained based on the amplitude signal and phase signal corresponding to the second echo signal.

[0010] For example, obtaining a longitudinal relaxation time map based on a first echo signal, a first echo time, a second echo signal, a second echo time, a first flip angle, and a second flip angle includes: acquiring the sequence repetition time; determining the first echo signal and the second echo signal corresponding to the same echo time in the first echo time and the second echo time; determining the longitudinal relaxation attenuation factor based on the first echo signal, the second echo signal, the first flip angle, and the second flip angle; and obtaining the longitudinal relaxation time map based on the longitudinal relaxation attenuation factor and the sequence repetition time.

[0011] For example, the target image includes a weighted imaging map, which includes at least one of a magnetic susceptibility-weighted imaging map, a proton density-weighted imaging map, a longitudinal relaxation time-weighted imaging map, and a transverse relaxation time-weighted imaging map. Data reconstruction based on a first echo signal, a first echo time, a second echo signal, a second echo time, a first flip angle, and a second flip angle is performed to generate the target image. This includes: performing magnetic susceptibility-weighted imaging reconstruction processing based on the amplitude signal and phase signal corresponding to the first echo signal to obtain a magnetic susceptibility-weighted imaging map; or performing magnetic susceptibility-weighted imaging reconstruction processing based on the amplitude signal and phase signal corresponding to the second echo signal to obtain a magnetic susceptibility-weighted imaging map; determining a proton density-weighted imaging map based on the first flip angle and the first echo time, wherein the first flip angle is less than the second flip angle; determining a longitudinal relaxation time-weighted imaging map based on the second flip angle and the second echo time; and determining a transverse relaxation time-weighted imaging map based on the first flip angle and the first echo time.

[0012] For example, the target image includes a weighted imaging map, which includes at least one of a magnetic susceptibility weighted imaging map, a proton density weighted imaging map, a longitudinal relaxation time weighted imaging map, and a transverse relaxation time weighted imaging map; data reconstruction is performed based on a first echo signal, a first echo time, a second echo signal, a second echo time, a first flip angle, and a second flip angle to generate the target image, including: adjusting the first flip angle, the second flip angle, the first echo time, the second echo time, and the sequence repetition time of the steady-state relational function based on the longitudinal relaxation time map, the proton density map, and the transverse relaxation time map to obtain at least one of the proton density weighted imaging map, the longitudinal relaxation time weighted imaging map, and the transverse relaxation time weighted imaging map, wherein the steady-state relational function characterizes the functional relationship between the echo signal and the longitudinal relaxation time map, the proton density map, the transverse relaxation time map, the first flip angle, the second flip angle, the first echo time, the second echo time, and the sequence repetition time.

[0013] For example, the target image includes a magnetic resonance angiography image; the target image is generated by data reconstruction based on the first echo signal, the first echo time, the second echo signal, the second echo time, the first flip angle, and the second flip angle, including: fitting and subtraction processing based on the second echo signal, the second echo time, the longitudinal relaxation time map, the transverse relaxation time map, the first flip angle, the second flip angle, and the steady-state relationship function to obtain the magnetic resonance angiography image.

[0014] Another embodiment of this application provides an image generation apparatus, comprising: a construction module, configured to perform a blank scan based on a perturbed gradient echo sequence to establish a first steady state and a second steady state, wherein the perturbed gradient echo sequence is alternately excited based on a first flip angle and a second flip angle, the first steady state represents the steady state corresponding to the first flip angle, and the second steady state represents the steady state corresponding to the second flip angle; an acquisition module, configured to perform a scan based on the perturbed gradient echo sequence to acquire a first echo signal corresponding to a first echo time in the first steady state, and to acquire a second echo signal corresponding to a second echo time in the second steady state; and a reconstruction module, configured to perform data reconstruction based on the first echo signal, the first echo time, the second echo signal, and the second echo time to generate a target image.

[0015] Another embodiment of this application provides an electronic device having a computer program stored thereon, which, when executed by a processor, implements the steps of the method of any of the above embodiments.

[0016] Another embodiment of this application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method of any of the above embodiments.

[0017] In the above embodiments, the image generation method includes: performing a blank scan based on a perturbed gradient echo sequence to establish a first steady state and a second steady state, wherein the perturbed gradient echo sequence is alternately excited based on a first flip angle and a second flip angle, the first steady state represents the steady state corresponding to the first flip angle, and the second steady state represents the steady state corresponding to the second flip angle; performing a scan based on the perturbed gradient echo sequence to obtain a first echo signal corresponding to a first echo time in the first steady state, and obtaining a second echo signal corresponding to a second echo time in the second steady state; and performing data reconstruction based on the first echo signal, the first echo time, the second echo signal, the second echo time, the first flip angle, and the second flip angle to generate a target image. A perturbation gradient echo sequence excited by alternating flip angles is employed, and each sequence is established in a steady state through a blank scan. Echo signals at different echo times are acquired in each steady state. The image is reconstructed by jointly using two sets of flip angles, two sets of echo times, and corresponding echo signals. Multiple sets of differentiated magnetization evolution information can be acquired simultaneously with a single scanning process, eliminating the need for multiple sequence switching and scanning, effectively reducing scanning time. The acquisition method of steady state with double flip angles provides sufficient independent data dimensions, reduces reconstruction fitting error, and improves the imaging accuracy and tissue differentiation ability of the reconstructed target image. Furthermore, the simultaneous acquisition of multiple sets of homologous signals eliminates the need for multi-sequence image registration, simplifying the reconstruction process and reducing computational overhead. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a data acquisition sequence provided in one embodiment; Figure 2 A schematic diagram of the acquisition sequence provided for another embodiment; Figure 3 A flowchart of an image generation method provided for an embodiment of this application; Figure 4 A schematic diagram of the scrambled gradient echo sequence structure provided in this application embodiment; Figure 5 A timing diagram of the scrambled gradient echo sequence provided for an embodiment of this application; Figure 6 Block diagram of an image generation method apparatus provided in another embodiment of this application; Figure 7 A block diagram of an electronic device provided for another embodiment of this application. Detailed Implementation

[0019] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0020] Magnetic resonance imaging (MRI) has become an indispensable tool in clinical diagnosis and basic research due to its advantages such as no ionizing radiation, high soft tissue resolution, multi-planar imaging, and multi-contrast imaging. With the development of precision medicine, traditional imaging methods that primarily rely on single-weighted images (such as...) are becoming increasingly important. Weighted or The qualitative diagnostic model, based on weighted averages, has gradually shifted towards quantitative imaging. Magnetic resonance imaging (MRI) multiparameter imaging technology has emerged to meet this need, enabling the simultaneous acquisition of multiple physical and physiological parameters of tissues in a single scan, such as longitudinal relaxation time. ), lateral relaxation time ( These quantitative parameters, such as proton density (PD), apparent diffusion coefficient (ADC), and magnetic susceptibility, eliminate the influence of equipment and scanning protocols, and can more objectively and accurately reflect the pathophysiological information of tissues, such as microstructure, cell density, and metabolic state. This provides richer imaging biomarkers for early disease diagnosis, differentiation between benign and malignant diseases, and efficacy evaluation.

[0021] Currently, the conventional method for obtaining the aforementioned multiple parameters mainly involves performing multiple independent scans. For example, first performing a multi-echo spin echo sequence scan to obtain... map, then perform a reverse recovery sequence scan to obtain The final step may require diffusion-weighted imaging to obtain the ADC image. This "step-by-step acquisition" mode has significant drawbacks, such as long scanning time, difficulty in image spatial registration, and inconsistent scanning parameters.

[0022] To address these issues, various imaging techniques have emerged in recent years aimed at simultaneously generating multiple parametric maps in a single acquisition. These include magnetic resonance fingerprinting (MRF), synthetic magnetic resonance imaging based on multiple inversion / multi-echo sequences (such as MAGiC), STAGE based on variable inversion angle / multi-echo sequences, and MTP based on variable inversion angle / multi-echo / dual TR (Repetition Time). These techniques significantly improve imaging efficiency and tissue quantification capabilities through specialized acquisition strategies and reconstruction methods. However, these existing simultaneous multi-parameter imaging methods still suffer from one or more technical bottlenecks, such as reconstruction accuracy and robustness, parameter coupling and error propagation, and sensitivity to motion.

[0023] In recent years, with the development of MRI technology, quantitative magnetic resonance imaging (qMRI) has gradually matured and been applied in clinical practice. Unlike conventional MRI, qMRI is a technique that uses MRI signals acquired under specific acquisition methods, followed by post-processing and reconstruction, to quantify magnetic resonance parameters. The quantitative images obtained by qMRI directly reflect the quantitative information of certain magnetic resonance parameters in biological tissues. The magnitude of these quantitative values ​​allows for intuitive differentiation and assessment of lesions, thus providing a more accurate basis for the diagnosis and analysis of clinical diseases.

[0024] In qMRI, conventional quantitative imaging techniques include Quantitative imaging ( mapping) Quantitative imaging ( PD mapping), PD quantitative imaging (PD mapping) (or R2) Quantitative imaging (or R2) ) mapping, where R2 =1 / And quantitative magnetic susceptibility imaging (QSM), etc.

[0025] exist In mapping techniques, two main methods are commonly used: Inversion Recovery (IR) and Variable Flip Angle (VFA). The T1 mapping method based on IR sequences requires setting different TI (Inversion Time) times for data acquisition. The MR (Magnetic Resonance) signals at different time points on the relaxation curve were obtained, and then the tissue was analyzed by fitting the exponential curve of the MR signals. Value. Based on the VFA method. The mapping technique requires setting multiple different flip angles for the sequence, and then calculating the result by fitting the MR signal to multiple points. value.

[0026] exist In mapping techniques, commonly used methods include SE sequences based on different echo times, MESE based on multiple echoes (multi-echo SE, MESE), and others. Methods such as magnetization for sequence preparation are employed. These methods all require acquiring MR signals with different echo times (TE), and then generating sequences through exponential curve fitting. map.

[0027] exist (or R2) In mapping techniques, a commonly used method is gradient echo (GRE) sequence based on multiple echoes. This method acquires MR signals of GRE sequences at different echo times and then... By fitting the exponential decay curve, we can obtain... (or R2) Measurement results.

[0028] In addition to the commonly used single-parameter qMRI techniques mentioned above, a multi-parameter imaging technique based on multi-dynamic multi-echo (MDME) spin-echo sequences (MAGiC) has been introduced. This technique uses saturated pulse excitation and multi-echo acquisition to obtain MR signals with different contrasts, and then generates MR signals through post-processing algorithms. , PD WI (Weighted Imaging) Images with varying contrast ratios, such as WI, were obtained. Specifically, multi-dynamic, multi-echo spin echo sequences were employed. By setting the delay times of the saturation pulse and excitation pulse in different dynamic states, as well as different echo times, different contrast ratios were achieved. and The relaxed MR signal is then used to calculate the signal through signal fitting. map and map; using the generated map and The PDmap is generated by combining the signal formula of the spin echo sequence with the map; the obtained quantitative parameters and MR signal formula are then used to synthesize... WI Images with conventional contrast, such as WI and FLAIR.

[0029] In one embodiment, a DESPOT1, DESPO is proposed. Methods for simultaneously obtaining and This method is based on the VFA method, using Spoiled Gradient Echo (SPGR) and Steady State Free Precession (SSFP) sequences to acquire SPGR and SSFP signals at different flip angles, respectively. The SPGR signal is then used to generate a map. map, and then based on the generated map and SSFP signal generation map.

[0030] In another embodiment, a STAGE (Strategically acquired gradient Echoimaging) acquisition strategy is proposed to simultaneously acquire quantitative maps of multiple parameters, weighted maps of multiple parameters, and images of multiple blood vessels. Specifically, a schematic diagram of the sequence is shown below. Figure 1 As shown. This technique employs a multi-echo gradient echo sequence, using multiple scans. The flip angle of the first scan is θ1, and the repetition time is TR (Repetition Time). It adopts a design approach of full flow compensation for gradients in all directions (corresponding to...). Figure 1 The FC (Flow Compensation) module in the middle collects echo data respectively. 11 to echo 1N A total of N echo signals were collected; the sequence flip angle of the second scan was θ2, the repetition time was also TR, and the other sequence structures were completely identical to the sequence of the first scan. Echo signals were collected separately. 21to echo 2N There are a total of N echo signals. Based on the VFA principle, STAGE uses signals with the same echo time but different flip angles to generate the signal. Map image. Based on multi-echo imaging. (or R2) Based on the mapping principle, STAGE generates signals from different echoes at any flip angle. (or R2) In addition, STAGE also utilizes the generated map. map and (or R2) STAGE generates a PDmap by combining the gradient echo signal formula and generates a QSM image using multiple echo signals at any flip angle. Based on the SWI (Susceptibility-Weighted Imaging) reconstruction principle, STAGE also generates magnetic susceptibility-related contrasts, including SWI and SWI phase maps. In addition to these contrasting images, STAGE also obtains conventional contrast images by utilizing the sequence features of different flip angles and echo times, including... WI, PDWI, WI et al.

[0031] In another embodiment, a STAGE-like MTP (Multi-parametric MRImaging) acquisition strategy is proposed to simultaneously acquire at least one sequence containing... map Various quantitative images, including map, PDmap, QSM, etc., as well as various weighted maps and vascular images. Specifically, a schematic diagram of the sequence is shown below. Figure 2 As shown, FM (Flow Modulation) represents the blood flow modulation module. This acquisition strategy is based on variable flip angle technology, dual TR technology, flow rate compensation technology, and flow rate encoding technology. In the first scan, the sequence flip angle is a1, and the times of the two TRs are TR1 and TR2, respectively. N1 echo signals are acquired within TR1, and N2 echo signals are acquired within TR2. In the second scan, the flip angle is a2, and the times of the two TRs are also TR1 and TR2, acquiring N1 and N2 echoes. Based on the VFA principle, MTP technology uses signals from the same echo at different flip angles to obtain... map. Based on multi-echo. Imaging principle: MTP uses signals from different echoes at any flip angle to generate... (or R2) PDmap. In PDmap calculation, this strategy utilizes the previously generated map. map and (or R2) The map is then substituted into the expression for the magnetic resonance signal to generate the PD measurement results. Finally, in QSM reconstruction, the MTP technique utilizes different echo signals within the same TR at any flip angle to generate a QSM image based on the QSM reconstruction principle. In addition to the quantitative images mentioned above, the MTP technique can also generate other images based on the characteristics of different TRs, flip angles, and echoes. WI, PDWI, Regular weighted images, including WI, etc.

[0032] In the aforementioned multi-parameter imaging techniques, MAGiC employs multi-dynamic, multi-echo spin-echo sequences. By adjusting the saturation pulse delay time and echo time, it acquires MR signals with different contrasts. It then combines the acquired MR data with signal formulas to generate... , PD quantitative images and WI MR images with various parameters such as WI and PDWI can be obtained; however, due to the characteristics of spin echo, MAGiC technology cannot obtain information related to magnetic susceptibility. (DESPO) / In the technology, this method generates DESPO is needed when mapping. of Quantitative results, as is well known, are subject to various interferences during the process of solving for MR parameters from MR signals, leading to a certain deviation between the measured results and the actual parameter values. Therefore, DESPO The calculation results will not only be affected by the error introduced by the SSFP signal measurement itself, but also by the DESPO error. The calculation error, this error will accompany DESP The calculation is further amplified, that is, DESP0 The measurement itself The map has some errors, DESPO Measurement Besides the errors caused by the SSFP signal itself, the map also has DESPO. The introduced error leads to DESP0 / The method's measurement accuracy is not high. Additionally, DESPO... / The MR signal is acquired using a single-echo sequence, therefore this method cannot be used for... (or R2) Mapping. Both STAGE and MTP techniques are based on double-flip-angle, multi-echo GRE sequences. The difference is that STAGE uses a single-TR acquisition strategy, while MTP uses a dual-TR acquisition strategy.

[0033] The advantage of STAGE technology lies in its ability to quickly acquire MR signals with different contrasts for multi-parameter imaging. However, because the data for each flip angle are acquired independently, positional deviations caused by motion between different flip angles can lead to severe artifacts and errors in the reconstructed quantitative and synthetic images. The dual-TR advantage of MTP technology is that it can simultaneously acquire tissue B1 field distribution maps, correcting for errors caused by B1 field inhomogeneity. Measurement errors exist, but this dual-TR acquisition strategy increases scan time and, like STAGE, is motion-sensitive. Furthermore, in MTP technology, The formula for calculating the relaxation time is an approximate solution to the MR signal (not the analytical solution in the STAGE), therefore theoretically... The measurement results of relaxation time have a certain degree of error.

[0034] To simultaneously acquire magnetic resonance images with multiple different parameters and enhance motion robustness and quantitative accuracy, this application aims to propose a bistable model-based multi-parameter magnetic resonance imaging method that can simultaneously acquire at least the following parameters in a single scan: map, PDmap (or R2) map, WI Magnetic resonance images with multiple parameters, including WI, PDWI, SWI, QSM, MRA, etc.

[0035] In view of this, this application proposes an image generation method that employs multi-parameter imaging. Based on a bistable model with variable flip angle, flow velocity compensation / coding technology, and multi-echo acquisition technology, it uses SPGR sequences to acquire magnetic resonance black-blood and bright-blood signals at different flip angles and echo times. Through the reconstruction and processing of different signals, it simultaneously generates at least the following: map (or R2) Quantitative images with various parameters, including )map, PDmap, and QSM, and WI (Longitudinal Relaxation Time-Weighted Image), PDWI (Proton Density Weighted Image) Various conventional weighted images and vascular images, including WI (lateral relaxation time-weighted image), SWI (susceptibility weighted image), and MRA.

[0036] Figure 3 A flowchart illustrating the image generation method provided in this application.

[0037] like Figure 3 As shown, the image generation method 300 provided in this application embodiment includes, for example, steps S310-S330.

[0038] Step S310: Perform a blank scan based on the perturbed gradient echo sequence to establish a first steady state and a second steady state. The perturbed gradient echo sequence is excited alternately based on a first flip angle and a second flip angle. The first steady state represents the steady state corresponding to the first flip angle, and the second steady state represents the steady state corresponding to the second flip angle.

[0039] For example, a pre-scan using a scrambled gradient echo sequence with alternating first and second flip angle radio frequency pulses is performed. During the pre-scan, no echo signal is acquired; only multiple rounds of radio frequency pulse cyclic excitation are continuously completed. This causes the magnetization vector to gradually converge to a periodically stable magnetization state under the pulse excitation at the corresponding first and second flip angles, thus forming a first steady state and a second steady state. The pre-scan typically requires 4 to 10 pre-scans (the exact number depends on the TR and the T1 value of the tissue).

[0040] Step S320: Perform scanning processing based on the perturbed gradient echo sequence to obtain the first echo signal corresponding to the first echo time under the first steady state, and obtain the second echo signal corresponding to the second echo time under the second steady state.

[0041] For example, when the radio frequency pulse cycle reaches the first steady-state stage, radio frequency excitation is performed once using a first flip angle within the sequence repetition time. Echo signals are acquired at a preset first echo time, resulting in a first echo signal with stable amplitude. Since there are multiple first echo times, multiple echo signals corresponding to the first echo times can be obtained as the first echo signal. Similarly, when the radio frequency pulse cycle reaches the second steady-state stage, radio frequency excitation is performed once using a second flip angle within the sequence repetition time. Echo signals are acquired at a preset second echo time, resulting in a second echo signal with stable amplitude. Since there are multiple second echo times, multiple echo signals corresponding to the second echo times can be obtained as the second echo signal. The scrambled gradient echo sequence includes multiple sequence repetition times. Within these multiple sequence repetition times... Alternately execute the radio frequency excitation corresponding to the first and second flip angles, respectively.

[0042] Step S330: Data reconstruction is performed based on the first echo signal, the first echo time, the second echo signal, the second echo time, the first flip angle, and the second flip angle to generate the target image.

[0043] For example, the target image may include quantitative images, weighted imaging images, magnetic resonance angiography (MRA), etc., and the quantitative images may include longitudinal relaxation time maps (…). ), lateral relaxation time plot ( Proton density maps (PD) and quantitative susceptibility mapping (QSM) are used, and weighted imaging maps include magnetic susceptibility-weighted imaging (SWI), proton density-weighted imaging (PDWI), and longitudinal relaxation time-weighted imaging (LWTI). WI) and lateral relaxation time-weighted plot ( The target image is not limited to the images mentioned above (WI), and is not intended to limit this application.

[0044] In the above embodiments, alternating excitation of perturbed gradient echo sequences with double flip angles is used, and their respective steady states are established through empty scanning. Echo signals at different echo times are acquired under the steady state. The image is reconstructed by jointly using two sets of flip angles, two sets of echo times, and corresponding echo signals. Multiple sets of differentiated magnetization evolution information can be acquired simultaneously with only one scanning process, without the need for multiple sequence switching and scanning, effectively reducing scanning time. The acquisition method of steady state with double flip angles can provide sufficient independent data dimensions, reduce reconstruction fitting errors, and improve the imaging accuracy and tissue differentiation ability of the reconstructed target image. Moreover, the simultaneous acquisition of multiple sets of homologous signals does not require multi-sequence image registration, simplifying the reconstruction process and reducing computational overhead.

[0045] Figure 4 A schematic diagram of the perturbation gradient echo sequence structure provided in the embodiments of this application.

[0046] In some embodiments, the scrambled gradient echo sequence includes multiple sequence repetition times, the first echo time includes multiple times, and the second echo time includes multiple times. Scanning processing based on the scrambled gradient echo sequence to obtain a first echo signal corresponding to a first echo time in a first steady state, and to obtain a second echo signal corresponding to a second echo time in a second steady state, includes: within one sequence repetition time, performing radio frequency pulse excitation based on a first flip angle, and obtaining the corresponding first echo as a first echo signal at each first echo time; within the next sequence repetition time, performing radio frequency pulse excitation based on a second flip angle, and obtaining the corresponding second echo as a second echo signal at each second echo time, wherein, within multiple sequence repetition times, radio frequency pulse excitation corresponding to the first flip angle and the second flip angle are alternately executed.

[0047] Specifically, such as Figure 4 As shown, based on the phase gradient echo sequence (SPGR), two different flip angles are used for alternating excitation. The flip angles are used to change alternately. That is, during RF pulse excitation, the odd-numbered flip angles are θ1 (first flip angle) and the even-numbered flip angles are θ2 (second flip angle). If the residual transverse magnetization vector at the end of each TR (sequence repetition time) is completely dephased, the longitudinal magnetization vector will eventually reach two different stable states, namely bistable states (first stable state and second stable state), as the excitation angle changes alternately.

[0048] Figure 5 A timing diagram of the scrambled gradient echo sequence provided for an embodiment of this application.

[0049] like Figure 5 As shown, TR represents the sequence repetition time, and the repetition time is the same for the first and second steady states; θ1 and θ2 represent the flip angles of the bistable SPGR sequence. arrive This indicates the acquired multi-echo signal; FC represents the flow compensation gradient module (FC), and FE represents the flow encoding gradient module (FE). During the first sequence repetition time, radio frequency pulses are excited based on the first flip angle θ1, and at each first echo time ( - Obtain the corresponding first echo ( arrive (as the first echo signal) - During the next sequence repetition time, radio frequency pulse excitation is performed based on the second flip angle θ2, and at each second echo time ( - Obtain the corresponding second echo ( arrive (as the second echo signal) - This allows for alternating excitation based on the first and second flip angles during multiple sequence repetition times.

[0050] In some embodiments, acquiring the corresponding first echo as the first echo signal at each first echo time includes: performing flow velocity compensation gradient processing on the acquired previous first echo before each first echo time to obtain the processed first echo, wherein the processed first echo includes a bright blood signal; and using the processed first echo as the first echo signal.

[0051] Specifically, such as Figure 5 As shown, for each first echo time ( - Before acquiring the echo signal, it will pass through the FC flow compensation gradient module (FC) for flow compensation processing to obtain the processed first echo. arrive ) as the first echo signal ( - ).

[0052] In some embodiments, acquiring the corresponding second echo as the second echo signal at each second echo time includes: performing flow velocity compensation gradient processing on the acquired previous second echo before each second echo time except for the last second echo time to obtain a processed second echo, wherein the processed second echo includes a bright blood signal; performing flow velocity encoding gradient processing on the processed second echo before the last second echo time to obtain an encoded second echo, wherein the encoded second echo includes a dark blood signal; and using the processed second echo and the encoded second echo as the second echo signal.

[0053] Specifically, such as Figure 5 As shown, for each second echo time except the last second echo time ( - Before acquiring the echo signal, it will pass through the FC flow compensation gradient module (FC) for flow compensation processing to obtain the processed second echo. arrive ), and based on the flow encoding gradient module (FE), the second echo time of the N-1th time. The processed second echo Flow velocity encoding gradient processing is performed to obtain the encoded second echo. The processed second echo ( arrive The second echo after encoding processing As the second echo signal ( - ).

[0054] In another alternative implementation, the step of acquiring the echo signal before the first to (N-1)th second echo times can be omitted. - The front-end multiple FC flow compensation gradient modules only in - Acquire the second echo that has not been processed by the flow compensation gradient module ( arrive ), at the Nth second echo time Before acquiring the echo signal, the second echo is processed using flow encoding (FE) based on the flow encoding gradient module to obtain... The corresponding second echo after encoding processing ,Will - The second echo acquired ( arrive ), The second echo after encoding and processing. As the second echo signal ( - ).

[0055] In some embodiments, the target image includes a quantitative map, which includes at least one of a longitudinal relaxation time map, a transverse relaxation time map, a proton density map, and a quantitative magnetic susceptibility imaging map; generating the target image by data reconstruction based on a first echo signal, a first echo time, a second echo signal, a second echo time, a first flip angle, and a second flip angle includes: obtaining a longitudinal relaxation time map based on the first echo signal, the first echo time, the second echo signal, the second echo time, the first flip angle, and the second flip angle.

[0056] For example, obtaining a longitudinal relaxation time map based on a first echo signal, a first echo time, a second echo signal, a second echo time, a first flip angle, and a second flip angle includes: acquiring the sequence repetition time; determining the first echo signal and the second echo signal corresponding to the same echo time in the first echo time and the second echo time; determining the longitudinal relaxation attenuation factor based on the first echo signal, the second echo signal, the first flip angle, and the second flip angle; and obtaining the longitudinal relaxation time map based on the longitudinal relaxation attenuation factor and the sequence repetition time.

[0057] Specifically, based on the established first and second steady states, the bistable model can be derived from the Bloch equation, as shown in formulas (1) and (2) below: (1) (2) In formulas (1) and (2), M0 represents the initial longitudinal magnetization vector, E1 represents the longitudinal relaxation attenuation factor, and M z1 M represents the longitudinal magnetization vector intensity in the first steady state. z2 This represents the longitudinal magnetization vector intensity in the second steady state. Specifically, when steady state is reached, M... z1 The longitudinal magnetization vector M before excitation at the corresponding flip angle θ1 z2 The longitudinal magnetization vector before excitation corresponding to the flip angle θ2.

[0058] Based on the above bistable model and the principle of magnetic resonance, the signal expression of the bistable SPGR sequence can be expressed as the following formulas (3) and (4): (3) (4) In formula (3) and formula (4), SD ssSPGR The signal strength of the bistable SPGR sequence is represented by M0; the initial magnetization vector strength is represented by θ1 and θ2; the flip angles of the bistable pulse sequence are represented by TR; the sequence repetition time is represented by T1; the longitudinal relaxation time is represented by TE; and the echo time is represented by T2. Indicates the lateral relaxation time. SD ssSPGR (θ1) corresponds to the first echo signal S acquired under the first steady state. 11 --S 1N amplitude signal, SD ssSPGR (θ2) corresponds to the second echo signal S acquired under the second steady state. 21 --S 2N The amplitude signal.

[0059] Based on formulas (3) and (4), we can obtain the following formula (5): (5) By transforming formula (5), the longitudinal relaxation attenuation factor E1 can be obtained, as shown in formula (6): (6) Therefore, the longitudinal relaxation time T1 can be obtained by solving formula (7): (7) The T1 calculation results can be obtained according to formulas (6) and (7). A T1 map (longitudinal relaxation time map) is generated based on multiple T1 calculation results.

[0060] A transverse relaxation time map is obtained by fitting the first echo signal and the first echo time, or by fitting the second echo signal and the second echo time.

[0061] Specifically, take the first echo signal S 11 S 12 …S 1N The amplitude signal, or the second echo signal S 21 S 22 …S 2N The amplitude signal is obtained by exponential fitting to obtain T2. Measured values, generate T2 map (lateral relaxation time plot) or R2 (Effective transverse relaxation rate), where R2 =1 / T2 .

[0062] Based on the longitudinal relaxation time map, the transverse relaxation time map, the first echo signal, the first echo time, the first flip angle, and the second flip angle, the initial magnetization vector intensity is determined, and the proton density map is obtained based on the initial magnetization vector intensity. Alternatively, based on the longitudinal relaxation time map, the transverse relaxation time map, the second echo signal, the second echo time, the first flip angle, and the second flip angle, the initial magnetization vector intensity is determined, and the proton density map is obtained based on the initial magnetization vector intensity.

[0063] Specifically, using the T1map and T2 calculated above... The amplitude signals of each echo (first echo signal or second echo signal) and the echo time and flip angle are collected. Combined with formulas (3) and (4), M0 (initial magnetization vector intensity) is obtained, thereby generating PDmap (proton density map).

[0064] A quantitative magnetic susceptibility imaging map is obtained based on the amplitude and phase signals corresponding to the first echo signal, or a quantitative magnetic susceptibility imaging map is obtained based on the amplitude and phase signals corresponding to the second echo signal.

[0065] Specifically, take the first echo signal S 11 S 12 …S 1N The amplitude and phase signals, or the second echo signal S. 21 S 22 …S 2N The amplitude and phase signals are used to generate a QSM image (quantitative susceptibility imaging map) based on the QSM reconstruction algorithm. Detailed calculations and analyses are not performed here.

[0066] In some embodiments, the target image includes a weighted imaging map, which includes at least one of a magnetic susceptibility-weighted imaging map, a proton density-weighted imaging map, a longitudinal relaxation time-weighted imaging map, and a transverse relaxation time-weighted imaging map; generating the target image by data reconstruction based on a first echo signal, a first echo time, a second echo signal, a second echo time, a first flip angle, and a second flip angle includes: performing magnetic susceptibility-weighted imaging reconstruction processing based on the amplitude signal and phase signal corresponding to the first echo signal to obtain a magnetic susceptibility-weighted imaging map, or performing magnetic susceptibility-weighted imaging reconstruction processing based on the amplitude signal and phase signal corresponding to the second echo signal to obtain a magnetic susceptibility-weighted imaging map.

[0067] Specifically, take the first echo signal S 11 S 12 …S1N The amplitude and phase signals, or the second echo signal S. 21 S 22 …S 2N The amplitude and phase signals are used to generate a SWI image (magnetic susceptibility weighted imaging map) based on the SWI reconstruction algorithm.

[0068] Based on the first flip angle and the first echo time, a proton density weighted map is determined, wherein the first flip angle is smaller than the second flip angle; based on the second flip angle and the second echo time, a longitudinal relaxation time weighted map is determined; based on the first flip angle and the first echo time, a transverse relaxation time weighted map is determined.

[0069] Specifically, the amplitude signals of the echo signals corresponding to small flip angles and short TE are used to generate PDWI (proton density weighted map); the amplitude signals of the echo signals corresponding to large flip angles and short TE are used to generate T1WI (longitudinal relaxation time weighted map); and the amplitude signals of the echo signals corresponding to small flip angles and long TE are used to generate T2WI. WI (Lateral Relaxation Time Weighted Plot). Here, we take θ1 (first flip angle) as a suitable small flip angle and θ2 (second flip angle) as a suitable large flip angle as an example. PDWI is S. 11 The corresponding amplitude signal (the amplitude signal of the first echo signal corresponding to the first echo time), T1WI is S 21 The corresponding amplitude signal (the amplitude signal of the second echo signal corresponding to the second echo time), T2 WI is S 1N The corresponding amplitude signal (the amplitude signal of the first echo signal corresponding to the first echo time).

[0070] In some embodiments, the target image includes a weighted imaging map, which includes at least one of a magnetic susceptibility weighted imaging map, a proton density weighted imaging map, a longitudinal relaxation time weighted imaging map, and a transverse relaxation time weighted imaging map; data reconstruction is performed based on a first echo signal, a first echo time, a second echo signal, a second echo time, a first flip angle, and a second flip angle to generate the target image, including: adjusting the first flip angle, the second flip angle, the first echo time, the second echo time, and the sequence repetition time of the steady-state relational function based on the longitudinal relaxation time map, the proton density map, and the transverse relaxation time map to obtain at least one of the proton density weighted imaging map, the longitudinal relaxation time weighted imaging map, and the transverse relaxation time weighted imaging map, wherein the steady-state relational function characterizes the functional relationship between the echo signal and the longitudinal relaxation time map, the proton density map, the transverse relaxation time map, the first flip angle, the second flip angle, the first echo time, the second echo time, and the sequence repetition time.

[0071] Specifically, take the T1map, PDmap, and T2 maps obtained from the above calculations. The amplitude signals of different flip angles (first flip angle and second flip angle) and different echo signals (first echo signal and second echo signal) are obtained from the map and combined with the bistable signal formula (such as formula (3) and formula (4)) (steady-state relationship function). By selecting appropriate parameters such as TR, TE and flip angle, images with different contrasts (proton density weighted map, longitudinal relaxation time weighted map and transverse relaxation time weighted map) are simulated and synthesized.

[0072] For example, setting a short TE, a small flip angle, and a long TR time generates a PDWI (proton density-weighted map); setting a short TE, a large flip angle, and a short TR time generates a T1WI (longitudinal relaxation time-weighted map); setting a long TE, a small flip angle, and a long TR time generates a T2WI. WI (Lateral Relaxation Time Weighted Map). For example, calculating T1map, PDmap, and T2... Substituting the longitudinal relaxation attenuation factors map, M0, and E1 into formula (3) or formula (4), and adjusting parameters such as TR, TE, and flip angle during calculation, a simulated echo signal is generated. Based on the simulated echo signal, the proton density weighted map, longitudinal relaxation time weighted map, and transverse relaxation time weighted map are calculated.

[0073] In some embodiments, the target image includes a magnetic resonance angiography image; the target image is generated by data reconstruction based on a first echo signal, a first echo time, a second echo signal, a second echo time, a first flip angle, and a second flip angle, including: fitting and subtraction processing based on the second echo signal, the second echo time, a longitudinal relaxation time map, a transverse relaxation time map, a first flip angle, a second flip angle, and a steady-state relational function to obtain the magnetic resonance angiography image.

[0074] Specifically, take the second echo signal S 21 S 22 …S 2N The amplitude signal, where S 21 …S 2（N-1） The corresponding amplitude signal is the blood flow signal with flow velocity compensation, S 2N The corresponding amplitude signal is the flow velocity encoded black blood signal, using the T2 generated above. map (lateral relaxation time plot), second echo signal, second echo time ( The longitudinal relaxation time diagram, the first flip angle, and the second flip angle are obtained by fitting the signal formula (such as formula (4)) (steady-state relationship function) to obtain the relationship with S at the second echo time. 2N Consistent, fitted bright blood signal SD ssSPGR (θ2), and then with the collected S 2NThe corresponding dark blood signal is subtracted to generate an MRA image (magnetic resonance angiography).

[0075] In another embodiment, the image generation method is not limited to the image types mentioned above; it can also combine other image algorithms to generate images with more contrast levels, such as combining the tSWI (True Susceptibility Weighted Imaging) reconstruction algorithm to generate tSWI images. This applies to generating T1WI, PDWI, and T2WI images. When generating images with these conventional contrast ratios, they can be derived from the amplitude images of echo signals acquired using appropriate sequence parameters, or from images synthesized from generated map plots and individual echo signals using signal formulas.

[0076] In another embodiment, the image generation method is not limited to generating T1WI, PDWI, and T2WI through synthesis. These conventional contrast images (WI) can be used to synthesize images with other contrast ratios based on signal formulas for other contrast ratios, such as DIR (Double Inversion Recovery) and FLAIR (Fluid-Attenuated Inversion Recovery). The bistable model proposed in this application does not limit the size of the flip angle used; the first flip angle can be smaller than the second flip angle, or the first flip angle can be larger than the second flip angle. Furthermore, when establishing a steady state, the bistable model proposed in this application can use a certain amount of empty scanning to ensure that the signal is in a steady state during formal acquisition, or it can use a certain k-space encoding trajectory to ensure that non-steady-state signals do not affect the contrast of the bistable signals (for example, acquiring signals gradually from the edge region of k-space towards the center; by the time the signal in the center region of k-space is acquired, the bistable condition has already been established, and the signal in the edge region of k-space will not affect the overall contrast of the two steady-state images).

[0077] In another embodiment, the image generation method employs a multi-parameter imaging sequence acquisition strategy. This strategy is based on the proposed bistable model of the SPGR sequence and uses flow rate compensation / coding technology and a multi-echo acquisition strategy. However, it is not limited to the flow rate compensation / coding technology and the number of echoes used. For example, using only a single echo can achieve fast T1 mapping, or only acquiring multiple echoes can generate T1 map and T2 map. map and PDmap.

[0078] In another embodiment, the bistable model of the SPGR sequence proposed by the image generation method can be either a 2D imaging sequence or a 3D imaging sequence.

[0079] The image generation method proposed in this application is based on a bistable model for multi-parameter imaging. This method achieves bistable imaging through a variable flipping mechanism, combined with flow velocity compensation / coding technology and multi-echo acquisition. By acquiring magnetic resonance black-blood and bright-blood signals at different steady states and echo times, and after a series of reconstructions and processing, it generates at least T1map and T2map images. map, PDmap, QSM, SWI, T1WI, PDWI, T2 Magnetic resonance images with various parameters, including WI and MRA, are used. Specifically, a certain scanning strategy is employed to establish a bistable magnetic resonance signal; multiple echo gradient echo signals are acquired in the first steady state (flip angle θ1) and filled into the corresponding k-space; multiple echo gradient echo signals are acquired in the second steady state (flip angle θ2) and filled into the corresponding k-space; the signals in each k-space are reconstructed to generate image domain signals for the corresponding steady state and echo time; T1map is generated using amplitude signals with different flip angles and the same echo time; T2map is generated using amplitude signals with the same flip angle and different echo times. (or R2) map; use the generated T1map and T2map. PDmap is generated from the amplitude signals of each flip angle and echo; T1WI is generated using the amplitude signals with large flip angles and short echo times; PDWI is generated using the amplitude signals with small flip angles and short echo times; T2WI is generated using the amplitude signals with small flip angles and long echo times. WI; SWI is generated using amplitude and phase signals with different echo times; QSM is generated using phase signals with different echo times; MRA (Magnetic Resonance Angiography) images are generated using subtraction techniques with amplitude signals of blood flow velocity compensation and flow velocity encoding at the same flip angle (the echo of flow velocity compensation is a bright blood signal, and the echo of flow velocity encoding is a dark blood signal).

[0080] Figure 6 A block diagram of an image generation apparatus provided for another embodiment of this application.

[0081] This specification provides an image generation apparatus 600 according to embodiments. Please refer to [link / reference]. Figure 6 The image generation device 600 includes: a construction module 610, an acquisition module 620, and a reconstruction module 630.

[0082] Module 610 is used to perform air scan processing based on the perturbation gradient echo sequence to establish a first steady state and a second steady state. The perturbation gradient echo sequence is excited alternately based on a first flip angle and a second flip angle. The first steady state represents the steady state corresponding to the first flip angle, and the second steady state represents the steady state corresponding to the second flip angle. The acquisition module 620 is used to perform scanning processing based on the perturbed gradient echo sequence to acquire the first echo signal corresponding to the first echo time under the first steady state, and to acquire the second echo signal corresponding to the second echo time under the second steady state. The reconstruction module 630 is used to reconstruct data based on the first echo signal, the first echo time, the second echo signal, and the second echo time to generate a target image.

[0083] For example, the scrambled gradient echo sequence includes multiple sequence repetition times, the first echo time includes multiple times, and the second echo time includes multiple times; the acquisition module 620 is further configured to perform radio frequency pulse excitation based on a first flip angle within one sequence repetition time, and acquire the corresponding first echo as a first echo signal at each first echo time; in the next sequence repetition time, perform radio frequency pulse excitation based on a second flip angle, and acquire the corresponding second echo as a second echo signal at each second echo time, wherein, in the multiple sequence repetition times, radio frequency pulse excitation corresponding to the first flip angle and the second flip angle are alternately executed.

[0084] For example, the acquisition module 620 is further configured to perform flow velocity compensation gradient processing on the acquired previous first echo before each first echo time to obtain a processed first echo, wherein the processed first echo includes a bright blood signal; and use the processed first echo as the first echo signal.

[0085] For example, the acquisition module 620 is further configured to perform flow velocity compensation gradient processing on the acquired previous second echo before each of the remaining second echo times except the last second echo time, to obtain a processed second echo, wherein the processed second echo includes a bright blood signal; before the last second echo time, perform flow velocity encoding gradient processing on the processed second echo to obtain an encoded second echo, wherein the encoded second echo includes a black blood signal; and use the processed second echo and the encoded second echo as the second echo signal.

[0086] For example, the target image includes a quantitative map, which includes at least one of a longitudinal relaxation time map, a transverse relaxation time map, a proton density map, and a quantitative magnetic susceptibility imaging map; the reconstruction module 630 is further configured to obtain a longitudinal relaxation time map based on a first echo signal, a first echo time, a second echo signal, a second echo time, a first flip angle, and a second flip angle; perform fitting processing based on the first echo signal and the first echo time to obtain a transverse relaxation time map, or perform fitting processing based on the second echo signal and the second echo time to obtain a transverse relaxation time map; and perform fitting processing based on the longitudinal relaxation time map and the transverse relaxation time map. The initial magnetization vector intensity is determined based on the first echo signal, the first echo time, the first flip angle, and the second flip angle. A proton density map is obtained based on the initial magnetization vector intensity. Alternatively, the initial magnetization vector intensity is determined based on the longitudinal relaxation time map, the transverse relaxation time map, the second echo signal, the second echo time, the first flip angle, and the second flip angle. A proton density map is obtained based on the initial magnetization vector intensity. A quantitative magnetic susceptibility imaging map is obtained based on the amplitude and phase signals corresponding to the first echo signal. Alternatively, a quantitative magnetic susceptibility imaging map is obtained based on the amplitude and phase signals corresponding to the second echo signal.

[0087] For example, the reconstruction module 630 is further configured to acquire the sequence repetition time; determine the first echo signal and the second echo signal corresponding to the same echo time in the first echo time and the second echo time; determine the longitudinal relaxation attenuation factor based on the first echo signal, the second echo signal, the first flip angle and the second flip angle; and obtain the longitudinal relaxation time map based on the longitudinal relaxation attenuation factor and the sequence repetition time.

[0088] For example, the target image includes a weighted imaging map, which includes at least one of a magnetic susceptibility-weighted imaging map, a proton density-weighted imaging map, a longitudinal relaxation time-weighted imaging map, and a transverse relaxation time-weighted imaging map; the reconstruction module 630 is further configured to perform magnetic susceptibility-weighted imaging reconstruction processing based on the amplitude signal and phase signal corresponding to the first echo signal to obtain a magnetic susceptibility-weighted imaging map, or to perform magnetic susceptibility-weighted imaging reconstruction processing based on the amplitude signal and phase signal corresponding to the second echo signal to obtain a magnetic susceptibility-weighted imaging map; determine the proton density-weighted imaging map based on the first flip angle and the first echo time, wherein the first flip angle is less than the second flip angle; determine the longitudinal relaxation time-weighted imaging map based on the second flip angle and the second echo time; and determine the transverse relaxation time-weighted imaging map based on the first flip angle and the first echo time.

[0089] For example, the target image includes a weighted imaging map, which includes at least one of a magnetic susceptibility weighted imaging map, a proton density weighted imaging map, a longitudinal relaxation time weighted imaging map, and a transverse relaxation time weighted imaging map; the reconstruction module 630 is further configured to adjust the first flip angle, the second flip angle, the first echo time, the second echo time, and the sequence repetition time of the steady-state relational function based on the longitudinal relaxation time map, the proton density map, and the transverse relaxation time map to obtain at least one of the proton density weighted imaging map, the longitudinal relaxation time weighted imaging map, and the transverse relaxation time weighted imaging map, wherein the steady-state relational function characterizes the functional relationship between the echo signal and the longitudinal relaxation time map, the proton density map, the transverse relaxation time map, the first flip angle, the second flip angle, the first echo time, the second echo time, and the sequence repetition time.

[0090] For example, the target image includes a magnetic resonance angiography image; the reconstruction module 630 is also used to perform fitting and subtraction processing based on the second echo signal, the second echo time, the longitudinal relaxation time map, the transverse relaxation time map, the first flip angle, the second flip angle and the steady-state relationship function to obtain the magnetic resonance angiography image.

[0091] Figure 7 A block diagram of an electronic device provided for another embodiment of this application.

[0092] Another embodiment of this application provides an electronic device having a computer program stored thereon, which, when executed by a processor, implements the steps of the method of any of the above embodiments.

[0093] like Figure 7 As shown, for ease of understanding, an embodiment of this application illustrates a specific electronic device 700.

[0094] Electronic device 700 is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. Electronic device 700 may also represent various forms of mobile devices, such as personal digital processors, cellular phones, smartphones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely illustrative and are not intended to limit the implementation of the present disclosure described and / or claimed herein.

[0095] like Figure 7As shown, the electronic device 700 includes a computing unit 701, which can perform various appropriate actions and processes according to a computer program stored in a read-only memory (ROM) 702 or a computer program loaded from a storage unit 708 into a random access memory (RAM) 703. The RAM 703 may also store various programs and data required for the operation of the electronic device 700. The computing unit 701, ROM 702, and RAM 703 are interconnected via a bus 704. An input / output (I / O) interface 705 is also connected to the bus 704.

[0096] Multiple components in electronic device 700 are connected to input / output (I / O) interface 705. These components include: input unit 706, such as a keyboard or mouse; output unit 707, such as various types of displays or speakers; storage unit 708, such as a disk or optical disk; and communication unit 709, such as a network interface card (NIC), modem, or wireless transceiver. Communication unit 709 allows electronic device 700 to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks.

[0097] The computing unit 701 can be a variety of general-purpose and / or special-purpose processing components with processing and computing capabilities. Some examples of the computing unit 701 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various special-purpose artificial intelligence (AI) computing chips, various computing units running machine learning model algorithms, a digital signal processor (DSP), and any suitable processor, controller, microcontroller, etc. The computing unit 701 performs the various methods described above. For example, in some embodiments, any one or more of the various methods described above can be implemented as a computer software program, which is tangibly contained in a machine-readable medium, such as storage unit 708. In some embodiments, part or all of the computer program can be loaded and / or installed on the electronic device 700 via ROM 702 and / or communication unit 709. When the computer program is loaded into RAM 703 and executed by the computing unit 701, one or more steps of any one or more of the various methods described above can be performed. Alternatively, in other embodiments, the computing unit 701 can be configured to perform any one or more of the various methods described above by any other suitable means (e.g., by means of firmware).

[0098] This application provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the method in any of the above embodiments.

[0099] The embodiments of the above-mentioned multi-parameter imaging methods include MAGiC technology, which is based on spin echo sequences and therefore cannot obtain magnetic susceptibility information. The bistable model proposed in this application, when using multi-echo sequences, can obtain images with various magnetic susceptibility contrasts, such as QSM, SWI, and SWI phase maps. The DESPOT1 / T2 method is an earlier proposed multi-parameter quantitative imaging method; however, due to its low accuracy and the sensitivity of the SSFP sequence to magnetic field inhomogeneities, which can cause image artifacts, this method is rarely used clinically. In addition to the above methods, STAGE is a method proposed in recent years based on a special acquisition strategy to achieve multi-parameter imaging. This method inherits the advantages of GRE sequences and can obtain conventional quantitative, magnetic susceptibility quantitative, conventional weighted, magnetic susceptibility weighted, and some synthetic images. However, this method is essentially based on a monostable SPGR sequence, acquiring magnetic resonance signals with different flip angles and echo times through multiple acquisitions. This acquisition strategy is sensitive to factors such as motion during the acquisition process. When the positions of two acquired images deviate, it directly affects the final image reconstruction result, causing errors and artifacts in the calculation of quantitative and synthetic images. This application uses a bistable SPGR sequence to continuously acquire MR signals with different flip angles and echo times in the k-space domain. This effectively reduces the sensitivity of the STAGE acquisition process to motion and can obtain MR images with the same multiple parameters as the STAGE. Besides the STAGE method, the MTP technique can also obtain multi-parameter imaging with equally rich contrast. However, the MTP technique is based on dual TR sequences and, like STAGE, adopts a strategy of acquiring MR signals with different flip angles and echo times in stages. Therefore, the MTP technique is also sensitive to motion, and the dual TR sequence makes the total acquisition time longer than the STAGE method. More importantly, the signal formula in the dual TR model of MTP is an approximate solution when calculating T1map, which makes the quantitative results of MTP erroneous. Its accuracy is lower than that of STAGE, and also lower than the image generation method of the variable flip angle bistable model with analytical solution proposed in this application.

[0100] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this application, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which programs can be printed, because programs can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0101] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0102] In the description of this application, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this application, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0103] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0104] Furthermore, the terms "first," "second," etc., used in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying relative importance, or implicitly specifying the number of technical features indicated in this embodiment. Therefore, features defined with terms such as "first" and "second" in the embodiments of this application can explicitly or implicitly indicate that the embodiment includes at least one of those features. In the description of this application, the word "multiple" means at least two or more, such as two, three, four, etc., unless otherwise explicitly and specifically defined in the embodiments.

[0105] In this application, unless otherwise explicitly specified or limited in the embodiments, the terms "installation," "connection," "joining," and "fixing" appearing in the embodiments should be interpreted broadly. For example, a connection can be a fixed connection, a detachable connection, or an integral part; it can also be a mechanical connection, an electrical connection, etc. Of course, it can also be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication between two components, or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific implementation.

[0106] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0107] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. An image generation method, characterized in that, The method includes: A blank scan is performed based on the phase-scraped gradient echo sequence to establish a first steady state and a second steady state. The phase-scraped gradient echo sequence is alternately excited based on a first flip angle and a second flip angle. The first steady state represents the steady state corresponding to the first flip angle, and the second steady state represents the steady state corresponding to the second flip angle. Based on the scrambled gradient echo sequence, a scanning process is performed to obtain the first echo signal corresponding to the first echo time under the first steady state, and to obtain the second echo signal corresponding to the second echo time under the second steady state. The target image is generated by reconstructing data based on the first echo signal, the first echo time, the second echo signal, the second echo time, the first flip angle, and the second flip angle.

2. The method according to claim 1, characterized in that, The perturbation gradient echo sequence includes multiple sequence repetition times, the first echo time includes multiple times, and the second echo time includes multiple times; the scanning processing based on the perturbation gradient echo sequence to obtain the first echo signal corresponding to the first echo time under the first steady state, and to obtain the second echo signal corresponding to the second echo time under the second steady state, includes: Within one repeating time of the sequence, radio frequency pulse excitation is performed based on the first flip angle, and the corresponding first echo is acquired as the first echo signal at each first echo time. During the next repeat time of the sequence, an radio frequency pulse is excited based on the second flip angle, and the corresponding second echo is acquired as the second echo signal at each second echo time. During the multiple repetition time intervals of the sequence, radio frequency pulse excitation corresponding to the first flip angle and the second flip angle is executed alternately.

3. The method according to claim 2, characterized in that, The step of acquiring the corresponding first echo as the first echo signal at each first echo time includes: Before each first echo time, the previously acquired first echo is subjected to velocity compensation gradient processing to obtain a processed first echo, wherein the processed first echo includes a bright blood signal. The processed first echo is taken as the first echo signal.

4. The method according to claim 2, characterized in that, The step of acquiring the corresponding second echo as the second echo signal at each second echo time includes: Before each second echo time except the last second echo time, the acquired previous second echo is subjected to velocity compensation gradient processing to obtain the processed second echo, wherein the processed second echo includes a bright blood signal. Before the last second echo time, the processed second echo is subjected to flow velocity encoding gradient processing to obtain an encoded second echo, wherein the encoded second echo includes a black blood signal. The processed second echo and the encoded second echo are used as the second echo signal.

5. The method according to claim 1, characterized in that, The target image includes a quantitative map, which includes at least one of a longitudinal relaxation time map, a transverse relaxation time map, a proton density map, and a quantitative magnetic susceptibility imaging map; the step of data reconstruction based on the first echo signal, the first echo time, the second echo signal, the second echo time, the first flip angle, and the second flip angle to generate the target image includes: Based on the first echo signal, the first echo time, the second echo signal, the second echo time, the first flip angle, and the second flip angle, a longitudinal relaxation time diagram is obtained; A transverse relaxation time map is obtained by fitting the first echo signal and the first echo time, or by fitting the second echo signal and the second echo time. Based on the longitudinal relaxation time map, the transverse relaxation time map, the first echo signal, the first echo time, the first flip angle, and the second flip angle, an initial magnetization vector intensity is determined, and a proton density map is obtained based on the initial magnetization vector intensity; or, based on the longitudinal relaxation time map, the transverse relaxation time map, the second echo signal, the second echo time, the first flip angle, and the second flip angle, an initial magnetization vector intensity is determined, and a proton density map is obtained based on the initial magnetization vector intensity. The quantitative magnetic susceptibility imaging map is obtained based on the amplitude signal and phase signal corresponding to the first echo signal, or the quantitative magnetic susceptibility imaging map is obtained based on the amplitude signal and phase signal corresponding to the second echo signal.

6. The method according to claim 5, characterized in that, The process of obtaining a longitudinal relaxation time map based on the first echo signal, the first echo time, the second echo signal, the second echo time, the first flip angle, and the second flip angle includes: Obtain the repetition time of the sequence; Determine the first echo signal and the second echo signal corresponding to the same echo time in the first echo time and the second echo time; Based on the first echo signal, the second echo signal, the first flip angle, and the second flip angle, the longitudinal relaxation attenuation factor is determined; Based on the longitudinal relaxation decay factor and the sequence repetition time, a longitudinal relaxation time map is obtained.

7. The method according to claim 1, characterized in that, The target image includes a weighted imaging map, which includes at least one of a magnetic susceptibility-weighted imaging map, a proton density-weighted imaging map, a longitudinal relaxation time-weighted imaging map, and a transverse relaxation time-weighted imaging map; the step of reconstructing the target image based on the first echo signal, the first echo time, the second echo signal, the second echo time, the first flip angle, and the second flip angle to generate the target image includes: Based on the amplitude signal and phase signal corresponding to the first echo signal, magnetic susceptibility weighted imaging reconstruction processing is performed to obtain a magnetic susceptibility weighted imaging map; or, based on the amplitude signal and phase signal corresponding to the second echo signal, magnetic susceptibility weighted imaging reconstruction processing is performed to obtain a magnetic susceptibility weighted imaging map. Based on the first flip angle and the first echo time, a proton density weighted map is determined, wherein the first flip angle is smaller than the second flip angle; Based on the second flip angle and the second echo time, a longitudinal relaxation time weighted map is determined; Based on the first flip angle and the first echo time, a weighted map of lateral relaxation time is determined.

8. The method according to claim 6, characterized in that, The target image includes a weighted imaging map, which includes at least one of a magnetic susceptibility-weighted imaging map, a proton density-weighted imaging map, a longitudinal relaxation time-weighted imaging map, and a transverse relaxation time-weighted imaging map; the step of reconstructing the target image based on the first echo signal, the first echo time, the second echo signal, the second echo time, the first flip angle, and the second flip angle to generate the target image includes: Based on the longitudinal relaxation time map, the proton density map, and the transverse relaxation time map, the first flip angle, the second flip angle, the first echo time, the second echo time, and the sequence repetition time are adjusted to obtain at least one of the proton density weighted map, the longitudinal relaxation time weighted map, and the transverse relaxation time weighted map. The steady-state relationship function characterizes the functional relationship between the echo signal and the longitudinal relaxation time map, the proton density map, the transverse relaxation time map, the first flip angle, the second flip angle, the first echo time, the second echo time, and the sequence repetition time.

9. The method according to claim 8, characterized in that, The target image includes a magnetic resonance angiography image; the process of reconstructing the target image based on the first echo signal, the first echo time, the second echo signal, the second echo time, the first flip angle, and the second flip angle includes: Based on the second echo signal, the second echo time, the longitudinal relaxation time map, the transverse relaxation time map, the first flip angle, the second flip angle, and the steady-state relationship function, fitting and subtraction processing are performed to obtain a magnetic resonance angiography image.

10. An image generation apparatus, characterized in that, The device includes: A construction module is used to perform air scan processing based on the perturbation gradient echo sequence to establish a first steady state and a second steady state. The perturbation gradient echo sequence is excited alternately based on a first flip angle and a second flip angle. The first steady state represents the steady state corresponding to the first flip angle, and the second steady state represents the steady state corresponding to the second flip angle. The acquisition module is used to perform scanning processing based on the perturbed gradient echo sequence to acquire the first echo signal corresponding to the first echo time under the first steady state, and to acquire the second echo signal corresponding to the second echo time under the second steady state. The reconstruction module is used to reconstruct data based on the first echo signal, the first echo time, the second echo signal, and the second echo time to generate a target image.

11. An electronic device having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method described in any one of claims 1-9.

12. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method described in any one of claims 1-9.

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