Pulsed steady-state CEST signal reconstruction method and apparatus, device, and storage medium

Abstract

The present application relates to the technical field of magnetic resonance. Disclosed are a pulsed steady-state CEST signal reconstruction method and apparatus, a device, and a storage medium. The method comprises: normalizing a first CEST signal and a second CEST signal to obtain an apparent Z-spectrum signal; calculating the longitudinal relaxation rate of water; establishing a function relational expression between the apparent Z-spectrum signal and target parameters, the target parameters comprising the longitudinal relaxation rate of water, the duty cycle of a pulsed radiofrequency saturation pulse, a pulse duration, and a relaxation delay time; acquiring a target Z-spectrum signal according to the function relational expression; and quantitatively analyzing the target Z-spectrum signal. The present application can obtain as the target Z-spectrum signal a steady-state Z-spectrum signal at the maximum extreme values of the pulse duration and the relaxation delay time, so as to obtain a target CEST signal approaching an ideal steady-state CEST signal, reducing effects of insufficiently long pulse duration and relaxation delay time on CEST signal quantification, and enhancing the CEST imaging capability of clinical magnetic resonance imaging systems.

Description

Reconstruction method, device, equipment and storage medium of pulsed steady-state CEST signal Technical Field

[0001] The present invention relates to the field of magnetic resonance technology, and in particular to a method, device, equipment and storage medium for reconstructing a pulsed steady-state CEST signal. Background Art

[0002] Chemical exchange saturation transfer (CEST) imaging is a magnetic resonance molecular imaging technique that can measure endogenous metabolites and compounds (such as glucose, glycogen, amide protons, etc.) as well as exogenous paramagnetic / diamagnetic CEST contrast agents, providing a new method for imaging a variety of diseases (such as stroke, tumors, epilepsy, etc.).

[0003] The CEST signal is closely related to scanning parameters such as the RF saturation pulse duration and relaxation delay time used to label the CEST contrast agent. Sufficiently long RF saturation pulse duration and relaxation delay time are prerequisites for obtaining an ideal steady-state CEST signal. However, due to limitations in total scan time, specific absorption rate (SAR), and hardware systems, CEST imaging often cannot be performed with sufficiently long RF saturation pulse duration and relaxation delay time. Consequently, the CEST signal obtained through CEST imaging is significantly lower than the ideal steady-state CEST signal.

[0004] Summary of the Invention

[0005] Based on this, it is necessary to address the technical problem that the existing technology cannot use sufficiently long RF saturation pulse duration and relaxation delay time for scanning, resulting in the CEST signal obtained by CEST imaging being significantly lower than the ideal steady-state CEST signal. A method, device, equipment and storage medium for reconstructing a pulsed steady-state CEST signal are proposed.

[0006] In a first aspect, a method for reconstructing a pulsed steady-state CEST signal is provided, the method comprising:

[0007] Acquiring a first CEST signal of a CEST contrast agent excited by a pulsed radiofrequency saturation pulse, a second CEST signal of a CEST contrast agent excited by a non-pulsed radiofrequency saturation pulse, T1mapping imaging, and scanning parameters, wherein the scanning parameters include pulse duration and relaxation delay time;

[0008] performing normalization processing on the first CEST signal and the second CEST signal to obtain an apparent Z spectrum signal;

[0009] Calculate the longitudinal relaxation rate of water based on the T1mapping imaging;

[0010] Establishing a functional relationship between the apparent Z spectrum signal and target parameters, wherein the target parameters include the longitudinal relaxation rate of the water, the duty cycle of the pulsed radio frequency saturation pulse, the pulse duration, and the relaxation delay time;

[0011] Acquire a target Z spectrum signal according to the functional relationship;

[0012] The target Z spectrum signal is quantitatively analyzed to obtain a target CEST signal.

[0013] In a second aspect, a device for reconstructing a pulsed steady-state CEST signal is provided, the device comprising:

[0014] an acquisition module, configured to acquire a first CEST signal of a CEST contrast agent excited by a pulsed radiofrequency saturation pulse, a second CEST signal of a CEST contrast agent excited by a non-pulsed radiofrequency saturation pulse, T1mapping imaging, and scanning parameters, wherein the scanning parameters include pulse duration and relaxation delay time;

[0015] A normalization module is used to perform normalization processing on the first CEST signal and the second CEST signal to obtain an apparent Z spectrum signal.

[0016] The reconstruction device of the pulsed steady-state CEST signal also includes:

[0017] A first acquisition module is used to acquire a first CEST signal of a CEST contrast agent excited by a pulsed radiofrequency saturation pulse, a second CEST signal of a CEST contrast agent excited by a non-pulsed radiofrequency saturation pulse, T1mapping imaging, and scanning parameters, wherein the scanning parameters include pulse duration and relaxation delay time;

[0018] a normalization module, configured to perform normalization processing on the first CEST signal and the second CEST signal to obtain an apparent Z spectrum signal;

[0019] A calculation module, configured to calculate the longitudinal relaxation rate of water based on the T1mapping imaging;

[0020] An establishment module is used to establish a functional relationship between the apparent Z spectrum signal and target parameters, wherein the target parameters include the longitudinal relaxation rate of the water, the duty cycle of the pulsed radio frequency saturation pulse, the pulse duration, and the relaxation delay time;

[0021] The second acquisition module acquires the target Z spectrum signal according to the functional relationship;

[0022] The analysis module is used to perform quantitative analysis on the target Z spectrum signal to obtain a target CEST signal.

[0023] In a third aspect, an electronic device is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method for reconstructing a pulsed steady-state CEST signal when executing the computer program.

[0024] In a fourth aspect, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the above-mentioned method for reconstructing a pulsed steady-state CEST signal are implemented.

[0025] The present invention proposes a method for reconstructing a pulsed steady-state CEST signal, which obtains a first CEST signal of a CEST contrast agent excited by a pulsed radio frequency saturation pulse, a second CEST signal of a CEST contrast agent excited by a non-pulsed radio frequency saturation pulse, T1mapping imaging, and scanning parameters, wherein the scanning parameters include pulse duration and relaxation delay time, and then normalizes the first CEST signal and the second CEST signal to obtain an apparent Z spectrum signal, thereby calculating the longitudinal relaxation rate of water according to the T1mapping imaging, and then establishing a functional relationship between the apparent Z spectrum signal and the target parameters, wherein the target parameters include the longitudinal relaxation rate of water, the pulsed radio frequency saturation pulse, and the second CEST signal. The duty cycle, the pulse duration and the relaxation delay time are determined, and then a target Z spectrum signal is obtained according to the functional relationship. Finally, the target Z spectrum signal is quantitatively analyzed to obtain a target CEST signal. The functional relationship between the apparent Z spectrum signal and the target parameter can be used to obtain a steady-state Z spectrum signal with the pulse duration and the relaxation delay time at the maximum limit values. The target Z spectrum signal is used as the target Z spectrum signal, and the target Z spectrum signal is quantitatively analyzed to obtain a target CEST signal that is close to an ideal steady-state CEST signal. The influence of insufficiently long pulse duration and relaxation delay time on the quantification of the CEST signal is reduced, thereby improving the accuracy of the quantification of the CEST signal and enhancing the CEST imaging capability of the clinical magnetic resonance imaging system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] in:

[0028] FIG1 is a diagram illustrating an application environment of a method for reconstructing a pulsed steady-state CEST signal in one embodiment;

[0029] FIG2 is a flow chart of a method for reconstructing a pulsed steady-state CEST signal in one embodiment;

[0030] FIG3 is a first experimental data diagram of a method for reconstructing a pulsed steady-state CEST signal in one embodiment;

[0031] FIG4 is a second experimental data diagram of a method for reconstructing a pulsed steady-state CEST signal in one embodiment;

[0032] FIG5 is a third experimental data diagram of a method for reconstructing a pulsed steady-state CEST signal in one embodiment;

[0033] FIG6 is a fourth experimental data diagram of a method for reconstructing a pulsed steady-state CEST signal in one embodiment;

[0034] FIG7 is a block diagram of a device for reconstructing a pulsed steady-state CEST signal according to one embodiment;

[0035] FIG8 is a structural block diagram of a clinical magnetic resonance apparatus according to an embodiment. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0037] In the following description, reference is made to “some embodiments”, which describes a subset of all possible embodiments, but it will be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein are for the purpose of describing the embodiments of this application only and are not intended to limit this application.

[0039] The present application provides a method, apparatus, device and storage medium for reconstructing a pulsed steady-state CEST signal.

[0040] The device for reconstructing the pulsed steady-state CEST signal can be specifically integrated into an electronic device, which can be a clinical magnetic resonance device, a smart phone, a tablet computer, a laptop computer, or a desktop computer, but is not limited thereto. The electronic device can be directly or indirectly connected to the server via wired or wireless communication. The server can be an independent physical server, or a server cluster or distributed system composed of multiple physical servers. It can also be a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communications, middleware services, domain name services, security services, CDN, and big data and artificial intelligence platforms. This application does not impose any restrictions on this.

[0041] For example, referring to FIG1 , the apparatus for reconstructing the pulsed steady-state CEST signal is integrated into a clinical magnetic resonance device. The clinical magnetic resonance device may include an interactive display screen, and a user may interact with the clinical magnetic resonance device through the display screen. The clinical magnetic resonance device reconstructs a pulsed steady-state CEST signal in response to a CEST signal reconstruction operation. For example, a user clicks a button corresponding to the CEST signal reconstruction on a display screen of the clinical magnetic resonance device to complete the CEST signal reconstruction operation. The steps of reconstructing the pulsed steady-state CEST signal include first acquiring a first CEST signal of a CEST contrast agent excited by a pulsed radio frequency saturation pulse, a second CEST signal of a CEST contrast agent excited by a non-pulsed radio frequency saturation pulse, T1mapping imaging, and scanning parameters, wherein the scanning parameters include pulse duration and relaxation delay time; then normalizing the first and second CEST signals to obtain an apparent Z spectrum signal, thereby calculating the longitudinal relaxation rate of water based on the T1mapping imaging; then establishing a functional relationship between the apparent Z spectrum signal and target parameters, wherein the target parameters include the longitudinal relaxation rate of water, the duty cycle of the pulsed radio frequency saturation pulse, the pulse duration, and the relaxation delay time; then acquiring a target Z spectrum signal based on the functional relationship; and finally quantitatively analyzing the target Z spectrum signal to obtain a target CEST signal.

[0042] The present application provides a method for reconstructing a pulsed steady-state CEST signal, which obtains a first CEST signal of a CEST contrast agent excited by a pulsed radiofrequency saturation pulse, a second CEST signal of a CEST contrast agent excited by a non-pulsed radiofrequency saturation pulse, T1mapping imaging, and scanning parameters, wherein the scanning parameters include pulse duration and relaxation delay time, and then the first CEST signal and the second CEST signal are reconstructed. The signal is normalized to obtain an apparent Z spectrum signal, thereby calculating the longitudinal relaxation rate of water according to the T1mapping imaging, and then establishing a functional relationship between the apparent Z spectrum signal and target parameters, wherein the target parameters include the longitudinal relaxation rate of water, the duty cycle of the pulsed radio frequency saturation pulse, the pulse duration, and the relaxation delay time. Then, a target Z spectrum signal is obtained according to the functional relationship, and finally, the target Z spectrum signal is quantitatively analyzed to obtain a target CEST signal. A steady-state Z spectrum signal with a pulse duration and a relaxation delay time at maximum limit values ​​can be obtained through the functional relationship between the apparent Z spectrum signal and the target parameters. The target Z spectrum signal is quantitatively analyzed to obtain a target CEST signal that is close to an ideal steady-state CEST signal, thereby reducing the influence of insufficiently long pulse duration and relaxation delay time on the quantification of the CEST signal, thereby improving the accuracy of the quantification of the CEST signal and enhancing the CEST imaging capability of the clinical magnetic resonance imaging system.

[0043] It should be noted that the order of description of the following embodiments does not limit the priority order of the embodiments.

[0044] Please refer to FIG. 2 , which is a flow chart of a method for reconstructing a pulsed steady-state CEST signal according to an embodiment of the present invention, including the following steps:

[0045] S101: Acquire a first CEST signal of a CEST contrast agent excited by a pulsed radiofrequency saturation pulse, a second CEST signal of a CEST contrast agent excited by a non-pulsed radiofrequency saturation pulse, T1mapping imaging, and scanning parameters, wherein the scanning parameters include pulse duration and relaxation delay time;

[0046] The CEST signal generated by excitation of a CEST contrast agent using a pulsed radiofrequency saturation pulse is used as the first CEST signal, and the CEST signal generated by excitation of a CEST contrast agent using an unpulsed radiofrequency saturation pulse is used as the second CEST signal. CEST contrast agents include exogenous and endogenous CEST contrast agents. Exogenous CEST contrast agents primarily include diamagnetic and paramagnetic CEST contrast agents. Endogenous CEST contrast agents primarily include amide, amine, and hydroxyl CEST contrast agents.

[0047] S102: performing normalization processing on the first CEST signal and the second CEST signal to obtain an apparent Z spectrum signal;

[0048] For example, the first CEST signal is divided by the second CEST signal to complete the normalization process and obtain a division result, which is the apparent Z spectrum signal.

[0049] S103: Calculate the longitudinal relaxation rate of water based on T1mapping imaging;

[0050] In one embodiment, the longitudinal relaxation rate of water is calculated based on T1mapping imaging with different inversion times; or, the longitudinal relaxation rate of water is calculated based on T1mapping imaging with different repetition times; or, the longitudinal relaxation rate of water is calculated based on T1mapping imaging with different flip angles.

[0051] S104: establishing a functional relationship between the apparent Z spectrum signal and target parameters, wherein the target parameters include the longitudinal relaxation rate of water, the duty cycle of the pulsed radio frequency saturation pulse, the pulse duration, and the relaxation delay time;

[0052] As an example, the longitudinal relaxation rate, the duty cycle of the pulsed radio frequency saturation pulse, the pulse duration, and the relaxation delay time are taken as target parameters, and a functional relationship between the apparent Z spectrum signal and the target parameters is established.

[0053] Furthermore, in one embodiment, establishing a functional relationship between the apparent Z spectrum signal and the target parameter includes:

[0054] Step A: Based on the off-resonance spin locking theory and the approximate expression of the steady-state CEST signal under the preset pulsed radio frequency saturation pulse excitation, a functional relationship between the apparent Z spectrum signal and the target parameter is established.

[0055] The approximate expression is expressed as follows:

[0056] Where θ = tan -1 (γ×B1÷Δω), γ is the gyromagnetic ratio = 42.6MHz / T, Δω is the RF saturation pulse frequency offset, B1 is the RF pulse marker energy, R 1ρ is the spin-lock relaxation rate, R 1w It refers to the longitudinal relaxation rate, and the duty cycle is DC.

[0057] S105: Acquire a target Z spectrum signal according to the functional relationship;

[0058] Specifically, a functional relationship is used to obtain a steady-state Z spectrum signal in which the pulse duration and the relaxation delay time are at maximum limit values, and the signal is used as a target Z spectrum signal.

[0059] Furthermore, in one embodiment, obtaining the target Z spectrum signal according to the functional relationship includes:

[0060] Step B, fitting the functional relationship to obtain a value of the spin-lock relaxation rate;

[0061] Step C: obtaining a target Z spectrum signal according to the value of the spin-locked relaxation rate and a preset Z spectrum reconstruction equation.

[0062] The functional relationship is expressed as follows:

[0063] Among them, I is the first CEST signal, I o is the second CEST signal, and the apparent Z spectrum signal is e is a natural constant, Ts is the pulse duration, and Td is the relaxation delay time.

[0064] The Z spectrum reconstruction equation is expressed as follows:

[0065] Wherein, Zss is the target Z spectrum signal, which refers to the steady-state Z spectrum signal when the pulse duration and relaxation delay time are at the maximum limit values.

[0066] S106: Quantitatively analyze the target Z spectrum signal to obtain a target CEST signal.

[0067] Specifically, a preset CEST quantitative algorithm is used to perform quantitative analysis on the target Z spectrum signal to obtain a target CEST signal. The preset CEST quantitative algorithm can be a conventional CEST quantitative method such as asymmetric analysis and multi-cell Lorentz fitting.

[0068] It should be noted that the feasibility of this invention has been confirmed through phantom testing. Representative results are as follows: Using PBS buffer, six 20mL creatine phantoms were prepared with a pH of 6.86, concentrations of 20mM, 40mM, and 60mM, and gadolinium contents of 4μL and 5μL, respectively. T1mapping imaging and CEST imaging were performed at a 3T magnetic resonance field strength with different inversion times (TIs). Imaging parameters such as imaging field of view and spatial resolution were consistent between the two. The TIs for T1mapping imaging were set to 200, 500, 800, 1100, and 1400ms, respectively, with a recovery time of 3000ms. The calculated T1w signal distribution is shown in Figure 3. For CEST imaging, the RF pulse marker energy B1 was set to 0.75μT, the duty cycle DC was 0.7, the pulse duration Ts and relaxation delay time Td were 1.5s / 1.5s and 3s / 3s, respectively, and the frequency offset range was -3.0 to 3.0ppm with a step size of 0.1ppm. The results of asymmetric analysis of the apparent CEST signal of creatine are shown in FIG4 .

[0069] Figure 4 includes CEST spectra of creatine mimetics corresponding to Ts / Td values ​​of 1.5s / 1.5s and 3s / 3s, respectively. Significant differences are evident between the different imaging parameters. When Ts / Td is 1.5s / 1.5s, the signals for the six creatine mimetics are 2.99±0.59%, 2.08±0.68%, 5.88±0.66%, 5.39±0.53%, 7.89±0.76%, and 7.45±0.80%, respectively. When Ts / Td is 3s / 3s, the signals for the six creatine mimetics are 3.74±0.54%, 2.53±0.64%, 7.31±0.54%, 6.63±0.62%, 10.04±0.73%, and 8.77±0.77%, respectively. It can be seen that the signals of the creatine mimetic show obvious differences due to different scanning times Ts / Td, confirming that insufficiently long pulse duration Ts and relaxation delay time Td affect the quantitative accuracy of the CEST signal.

[0070] As shown in Figure 5, Figure 5 shows the Z spectrum signals and asymmetric spectra corresponding to different Ts / Td scanning parameters. Before the reconstruction algorithm, there were significant differences in the Z spectrum and asymmetric spectra corresponding to different Ts / Td scanning parameters. However, this difference was significantly reduced after the reconstruction method of the pulsed steady-state CEST signal. Figure 5 includes (A) the apparent Z spectrum and (B) the corresponding asymmetric MTR in 60mM, 5μL gadolinium creatine phantom. asym Spectrum, and (C) Z spectrum after processing by the pulsed steady-state CEST signal reconstruction method and (D) corresponding MTR asym Score.

[0071] The distribution of creatine CEST signals after processing using the pulsed steady-state CEST signal reconstruction method is shown in Figure 6. When Ts / Td is 1.5s / 1.5s, the six creatine phantom signals are 4.34±0.88%, 2.82±0.93%, 7.99±0.97%, 6.93±0.67%, 10.90±1.09%, and 9.26±1.04%, respectively. When Ts / Td is 3s / 3s, the six creatine phantom signals are 4.41±0.57%, 2.86±0.68%, 7.70±0.58%, 6.86±0.65%, 10.65±0.78%, and 8.98±0.80%, respectively. Compared to pre-processing without pulsed steady-state CEST signal reconstruction, the differences in creatine CEST signals at different Ts / Td for the six creatine phantoms were significantly reduced, from 0.72±0.80%, 0.43±0.87%, 1.42±0.77%, 1.23±0.85%, 2.08±0.83%, and 1.25±1.11% to 0.33±1.05%, 0.16±1.07%, 0.29±1.02%, 0.06±0.98%, 0.22±1.07%, and 0.31±1.30%, respectively. The P-value for the significant difference within the groups increased from 0.004 to 0.111. Processing with the pulsed steady-state CEST signal reconstruction method improved the accuracy of CEST signal quantification under the influence of pulse duration Ts and relaxation delay time Td.

[0072] As shown in Figure 6, after processing using the pulsed steady-state CEST signal reconstruction method, the CEST spectra of the creatine phantom corresponding to Ts / Td of 1.5s / 1.5s and 3s / 3s were obtained. The consistency of the images between different imaging parameters was significantly improved.

[0073] The method for reconstructing a pulsed steady-state CEST signal proposed in this embodiment obtains a first CEST signal of a CEST contrast agent excited by a pulsed radio frequency saturation pulse, a second CEST signal of a CEST contrast agent excited by a non-pulsed radio frequency saturation pulse, T1mapping imaging, and scanning parameters, wherein the scanning parameters include pulse duration and relaxation delay time, and then normalizes the first CEST signal and the second CEST signal to obtain an apparent Z spectrum signal, thereby calculating the longitudinal relaxation rate of water according to the T1mapping imaging, and then establishing a functional relationship between the apparent Z spectrum signal and the target parameters, wherein the target parameters include the longitudinal relaxation rate of water, the pulsed radio frequency saturation pulse, and the second CEST signal. The duty cycle of the pulse, the pulse duration and the relaxation delay time are calculated, and then a target Z spectrum signal is obtained according to the functional relationship. Finally, the target Z spectrum signal is quantitatively analyzed to obtain a target CEST signal. The functional relationship between the apparent Z spectrum signal and the target parameter can be used to obtain a steady-state Z spectrum signal with the pulse duration and the relaxation delay time at the maximum limit values. The target Z spectrum signal is used as the target Z spectrum signal, and the target Z spectrum signal is quantitatively analyzed to obtain a target CEST signal that is close to an ideal steady-state CEST signal. The influence of insufficiently long pulse duration and relaxation delay time on the quantification of the CEST signal is reduced, thereby improving the accuracy of the quantification of the CEST signal and enhancing the CEST imaging capability of the clinical magnetic resonance imaging system.

[0074] Referring to FIG. 3 , in one embodiment, a device for reconstructing a pulsed steady-state CEST signal is provided. The device includes:

[0075] A first acquisition module 10 is configured to acquire a first CEST signal of a CEST contrast agent excited by a pulsed radiofrequency saturation pulse, a second CEST signal of a CEST contrast agent excited by a non-pulsed radiofrequency saturation pulse, T1mapping imaging, and scanning parameters, wherein the scanning parameters include pulse duration and relaxation delay time;

[0076] a normalization module 20, configured to perform normalization processing on the first CEST signal and the second CEST signal to obtain an apparent Z spectrum signal;

[0077] A calculation module 30, configured to calculate the longitudinal relaxation rate of water based on the T1mapping imaging;

[0078] An establishing module 40 is used to establish a functional relationship between the apparent Z spectrum signal and target parameters, wherein the target parameters include the longitudinal relaxation rate of the water, the duty cycle of the pulsed radio frequency saturation pulse, the pulse duration, and the relaxation delay time;

[0079] A second acquisition module 50 is configured to acquire a target Z spectrum signal according to the functional relationship;

[0080] The analysis module 60 is configured to perform quantitative analysis on the target Z spectrum signal to obtain a target CEST signal.

[0081] The calculation module 30 is further used to calculate the longitudinal relaxation rate of water based on T1mapping imaging with different inversion times; or, to calculate the longitudinal relaxation rate of water based on T1mapping imaging with different repetition times; or, to calculate the longitudinal relaxation rate of water based on T1mapping imaging with different flip angles.

[0082] The establishment module 40 is further used to establish a functional relationship between the apparent Z spectrum signal and the target parameter based on the off-resonance spin locking theory and an approximate expression of the steady-state CEST signal under preset pulsed radio frequency saturation pulse excitation.

[0083] The second acquisition module 50 is further configured to perform fitting calculation on the functional relationship to obtain a value of the spin-locked relaxation rate; and obtain a target Z spectrum signal based on the value of the spin-locked relaxation rate and a preset Z spectrum reconstruction equation.

[0084] In one embodiment, a clinical magnetic resonance device is provided, and its internal structure diagram can be shown in Figure 4. The clinical magnetic resonance device includes a processor, a memory, a network interface, and a database connected via a system bus. The processor of the clinical magnetic resonance device is used to provide computing and control capabilities. The memory of the clinical magnetic resonance device includes a non-volatile and / or volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and computer program in the non-volatile storage medium. The network interface of the clinical magnetic resonance device is used to communicate with an external client via a network connection. When the computer program is executed by the processor, it implements the functions or steps of a service-side method for reconstructing a pulsed steady-state CEST signal.

[0085] In one embodiment, a clinical magnetic resonance apparatus is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the following steps are implemented:

[0086] Acquiring a first CEST signal of a CEST contrast agent excited by a pulsed radiofrequency saturation pulse, a second CEST signal of a CEST contrast agent excited by a non-pulsed radiofrequency saturation pulse, T1mapping imaging, and scanning parameters, wherein the scanning parameters include pulse duration and relaxation delay time;

[0087] performing normalization processing on the first CEST signal and the second CEST signal to obtain an apparent Z spectrum signal;

[0088] Calculate the longitudinal relaxation rate of water based on the T1mapping imaging;

[0089] Establishing a functional relationship between the apparent Z spectrum signal and target parameters, wherein the target parameters include the longitudinal relaxation rate of the water, the duty cycle of the pulsed radio frequency saturation pulse, the pulse duration, and the relaxation delay time;

[0090] Acquire a target Z spectrum signal according to the functional relationship;

[0091] The target Z spectrum signal is quantitatively analyzed to obtain a target CEST signal.

[0092] The method for reconstructing a pulsed steady-state CEST signal proposed in this embodiment obtains a first CEST signal of a CEST contrast agent excited by a pulsed radio frequency saturation pulse, a second CEST signal of a CEST contrast agent excited by a non-pulsed radio frequency saturation pulse, T1mapping imaging, and scanning parameters, wherein the scanning parameters include pulse duration and relaxation delay time, and then normalizes the first CEST signal and the second CEST signal to obtain an apparent Z spectrum signal, thereby calculating the longitudinal relaxation rate of water based on T1mapping imaging, and then establishing a functional relationship between the apparent Z spectrum signal and the target parameters, wherein the target parameters include the longitudinal relaxation rate of water, the The duty cycle, the pulse duration and the relaxation delay time are determined, and then the target Z spectrum signal is obtained according to the functional relationship. Finally, the target Z spectrum signal is quantitatively analyzed to obtain a target CEST signal. The functional relationship between the apparent Z spectrum signal and the target parameter can be used to obtain a steady-state Z spectrum signal with the pulse duration and the relaxation delay time at the maximum limit values. The target Z spectrum signal is used as the target Z spectrum signal, and the target Z spectrum signal is quantitatively analyzed to obtain a target CEST signal that is close to the ideal steady-state CEST signal. The influence of insufficiently long pulse duration and relaxation delay time on the quantification of the CEST signal is reduced, thereby improving the accuracy of the quantification of the CEST signal and enhancing the CEST imaging capability of the clinical magnetic resonance imaging system.

[0093] In one embodiment, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the following steps are implemented:

[0094] Acquiring a first CEST signal of a CEST contrast agent excited by a pulsed radiofrequency saturation pulse, a second CEST signal of a CEST contrast agent excited by a non-pulsed radiofrequency saturation pulse, T1mapping imaging, and scanning parameters, wherein the scanning parameters include pulse duration and relaxation delay time;

[0095] performing normalization processing on the first CEST signal and the second CEST signal to obtain an apparent Z spectrum signal;

[0096] Calculate the longitudinal relaxation rate of water based on the T1mapping imaging;

[0097] Establishing a functional relationship between the apparent Z spectrum signal and target parameters, wherein the target parameters include the longitudinal relaxation rate of the water, the duty cycle of the pulsed radio frequency saturation pulse, the pulse duration, and the relaxation delay time;

[0098] Acquire a target Z spectrum signal according to the functional relationship;

[0099] The target Z spectrum signal is quantitatively analyzed to obtain a target CEST signal.

[0100] The method for reconstructing a pulsed steady-state CEST signal proposed in this embodiment is to obtain a first CEST signal of a CEST contrast agent excited by a pulsed radio frequency saturation pulse, a second CEST signal of a CEST contrast agent excited by a non-pulsed radio frequency saturation pulse, T1mapping imaging, and scanning parameters, wherein the scanning parameters include pulse duration and relaxation delay time, and then normalize the first CEST signal and the second CEST signal to obtain an apparent Z spectrum signal, thereby calculating the longitudinal relaxation rate of water based on T1mapping imaging, and then establish a functional relationship between the apparent Z spectrum signal and the target parameters, wherein the target parameters include the longitudinal relaxation rate of water, the pulsed radio frequency saturation pulse, and the second CEST signal. The duty cycle, the pulse duration and the relaxation delay time are determined, and then a target Z spectrum signal is obtained according to the functional relationship. Finally, the target Z spectrum signal is quantitatively analyzed to obtain a target CEST signal. The functional relationship between the apparent Z spectrum signal and the target parameter can be used to obtain a steady-state Z spectrum signal with the pulse duration and the relaxation delay time at the maximum limit values. The target Z spectrum signal is used as the target Z spectrum signal, and the target Z spectrum signal is quantitatively analyzed to obtain a target CEST signal that is close to an ideal steady-state CEST signal. The influence of insufficiently long pulse duration and relaxation delay time on the quantification of the CEST signal is reduced, thereby improving the accuracy of the quantification of the CEST signal and enhancing the CEST imaging capability of the clinical magnetic resonance imaging system.

[0101] It should be noted that the above functions or steps that can be implemented by the computer-readable storage medium or computer device can be found in the relevant descriptions of the server side and the client side in the aforementioned method embodiment. To avoid repetition, they will not be described one by one here.

[0102] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0103] Those skilled in the art will clearly understand that for the sake of convenience and brevity of description, only the division of the above-mentioned functional units and modules is used as an example. In actual applications, the above-mentioned functions can be distributed and completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

[0104] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the scope of protection of the present invention.

Claims

1. A method for reconstructing a pulsed steady-state CEST signal, characterized in that: The method comprises: Acquire a first CEST signal of a CEST contrast agent excited by a pulsed radio frequency saturation pulse, a second CEST signal of a CEST contrast agent excited by a non-pulsed radio frequency saturation pulse, T1mapping imaging, and scanning parameters, wherein the scanning parameters include pulse duration and relaxation delay time; Normalizing the first CEST signal and the second CEST signal to obtain an apparent Z spectrum signal; According to the T1mapping imaging, the longitudinal relaxation rate of water is calculated; Establishing a functional relationship between the apparent Z spectrum signal and target parameters, wherein the target parameters include the longitudinal relaxation rate of the water, the duty cycle of the pulsed radio frequency saturation pulse, the pulse duration, and the relaxation delay time; Acquire a target Z spectrum signal according to the functional relationship; The target Z spectrum signal is quantitatively analyzed to obtain a target CEST signal.

2. The method for reconstructing a pulsed steady-state CEST signal according to claim 1, characterized in that: The calculating of the longitudinal relaxation rate of water according to the T1mapping imaging comprises: Calculate the longitudinal relaxation rate of water based on T1mapping imaging with different inversion times; or, Calculate the longitudinal relaxation rate of water based on T1mapping imaging with different repetition times; or, The longitudinal relaxation rate of water was calculated based on T1mapping imaging at different flip angles.

3. The method for reconstructing a pulsed steady-state CEST signal according to claim 1, characterized in that: The step of establishing a functional relationship between the apparent Z spectrum signal and the target parameter comprises: Based on the off-resonance spin locking theory and the approximate expression of the steady-state CEST signal under the preset pulsed radio frequency saturation pulse excitation, a functional relationship between the apparent Z spectrum signal and the target parameter is established.

4. The method for reconstructing a pulsed steady-state CEST signal according to claim 3, characterized in that: The approximate expression is represented by the following formula: Where θ = tan -1 (γ×B1÷Δω), γ is the gyromagnetic ratio = 42.6MHz / T, Δω is the RF saturation pulse frequency offset, B1 is the RF pulse marker energy, R 1ρ is the spin-lock relaxation rate, R 1w refers to the longitudinal relaxation rate, and the duty cycle is DC.

5. The method for reconstructing a pulsed steady-state CEST signal according to claim 4, characterized in that: The step of acquiring the target Z spectrum signal according to the functional relationship includes: Fitting and calculating the functional relationship to obtain a value of the spin-lock relaxation rate; According to the value of the spin-locked relaxation rate and a preset Z spectrum reconstruction equation, a target Z spectrum signal is obtained.

6. The method for reconstructing a pulsed steady-state CEST signal according to claim 5, characterized in that: The functional relationship is expressed by the following formula: Wherein, I is the first CEST signal, I o is the second CEST signal, and the apparent Z spectrum signal is e is a natural constant, Ts is the pulse duration, and Td is the relaxation delay time.

7. The method for reconstructing a pulsed steady-state CEST signal according to claim 6, characterized in that: The Z-spectrum reconstruction equation is expressed by the following formula: Wherein, Zss is a target Z spectrum signal, and the target Z spectrum signal refers to a steady-state Z spectrum signal when the pulse duration and the relaxation delay time are at maximum limit values.

8. A device for reconstructing a pulsed steady-state CEST signal, characterized in that: The reconstruction device of the pulsed steady-state CEST signal comprises: The first acquisition module is used to acquire the first CEST signal of the CEST contrast agent excited by the pulsed radio frequency saturation pulse, the second CEST signal of the CEST contrast agent excited by the non-pulsed radio frequency saturation pulse, and the T1mapping Imaging and scanning parameters, wherein the scanning parameters include pulse duration and relaxation delay time; A normalization module, used for performing normalization processing on the first CEST signal and the second CEST signal to obtain an apparent Z spectrum signal; A calculation module, used for calculating the longitudinal relaxation rate of water according to the T1mapping imaging; An establishment module is used to establish a functional relationship between the apparent Z spectrum signal and target parameters, wherein the target parameters include the longitudinal relaxation rate of the water, the duty cycle of the pulsed radio frequency saturation pulse, the pulse duration, and the relaxation delay time; The second acquisition module acquires the target Z spectrum signal according to the functional relationship; The analysis module is used to perform quantitative analysis on the target Z spectrum signal to obtain a target CEST signal.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the processor implements the steps of the method for reconstructing the pulsed steady-state CEST signal according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method for reconstructing a pulsed steady-state CEST signal according to any one of claims 1 to 7 are implemented.

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