WO2022120531A1

WO2022120531A1 - Chemical exchange saturation transfer quantification method and apparatus for magnetic resonance, and medium

Info

Publication number: WO2022120531A1
Application number: PCT/CN2020/134317
Authority: WO
Inventors: 吴垠; 郑海荣; 刘新
Original assignee: 中国科学院深圳先进技术研究院
Priority date: 2020-12-07
Filing date: 2020-12-07
Publication date: 2022-06-16

Abstract

A chemical exchange saturation transfer (CEST) quantification method and apparatus (50) for magnetic resonance, and a medium, relating to the field of biomedical engineering. The quantification method comprises: obtaining a longitudinal relaxation rate of water (S11); presetting a variant equation for calculating a spin-lock relaxation rate of water under non-steady-state experiment conditions, at least one variant parameter of the variant equation being the ratio of a saturation signal to a non-saturation reference signal under the non-steady-state experiment conditions (S12); obtaining a plurality of parameters under the non-steady-state experiment conditions, and solving for the variant equation according to the parameters to obtain the spin-lock relaxation rate of water (S13); obtaining a magnetic resonance CEST signal under steady-state experiment conditions on the basis of the longitudinal relaxation rate of water and the spin-lock relaxation rate of water (S14); and obtaining a magnetic resonance CEST effect under the steady-state experiment conditions on the basis of the signal (S15). A steady-state CEST signal can be obtained by calculation on the basis of a non-steady-state CEST signal, the influence of imaging parameters on a CEST quantification result is eliminated, and the accuracy of CEST quantification is improved.

Description

Chemical exchange saturation transfer quantitative method, device and medium for magnetic resonance

【Technical field】

The present application relates to the field of biomedical engineering, in particular to a quantitative method, device and medium for chemical exchange saturation transfer for magnetic resonance.

【Background technique】

Magnetic resonance chemical exchange saturation transfer (CEST) imaging is an important imaging method for non-invasive acquisition of biological tissue molecular information using endogenous or exogenous CEST contrast agents. Sufficient saturation of the CEST contrast agent and sufficient recovery of the saturated water molecule signal are necessary conditions for obtaining a steady-state CEST signal and determine the accuracy of the quantification of the CEST effect.

The quantification of the CEST effect is very complex, affected by many factors, and is closely related to important imaging parameters such as saturation time (Ts) and recovery time (Td), that is, the quantitative results of CEST are highly dependent on imaging parameters. However, the saturation time is restricted by factors such as the hardware system and the specific absorption rate, and the long-term saturation and recovery will greatly increase the scanning time, which is very difficult in practical applications. In the prior art, most CEST imaging studies are usually carried out under the conditions of short saturation time and recovery time (that is, under non-steady-state experimental conditions), which cannot guarantee sufficient saturation and recovery, and the obtained CEST signal is also in non-steady state. This can lead to an underestimation of the CEST effect, preventing accurate and stable CEST quantification.

[Content of the invention]

The main technical problem to be solved by the present application is to provide a quantitative method, device and medium for chemical exchange saturation transfer for magnetic resonance. By presetting the deformation formula, the steady-state CEST signal can be calculated from the non-steady-state CEST signal, and based on the obtained steady state CEST signal A stable and accurate quantification of the CEST effect is achieved by using the state CEST signal.

In order to solve the above technical problems, a technical solution adopted in the present application is to provide a quantitative method for chemical exchange saturation transfer for magnetic resonance, the quantitative method includes: obtaining the longitudinal relaxation rate of water; presetting based on unsteady experimental conditions. The deformation formula for calculating the spin-lock relaxation rate of water under the following equation, at least one deformation parameter of the deformation formula is the ratio of the saturated signal under the unsteady experimental condition to the unsaturated reference signal; obtain the unsaturated reference under the unsteady experimental condition Signal and saturation signal, saturation time and recovery time, and calculate the deformation formula according to the non-saturated reference signal and saturation signal, saturation time and recovery time and the longitudinal relaxation rate of water under non-steady state experimental conditions to obtain the spin lock of water Relaxation rate; based on the longitudinal relaxation rate of water and the spin-lock relaxation rate of water, obtain the magnetic resonance chemical exchange saturation transfer signal under steady-state experimental conditions; based on the magnetic resonance chemical exchange saturation transfer signal under steady-state experimental conditions Obtain the magnetic resonance chemical exchange saturation transfer effect under steady state experimental conditions.

Wherein, a deformation formula for calculating the spin-lock relaxation rate of water under unsteady experimental conditions is preset, and at least one deformation parameter of the deformation formula is the ratio of the saturated signal to the non-saturated reference signal under the unsteady experimental conditions Specifically, it includes: obtaining the non-saturated reference signal and the calculation formula of the saturated signal under non-steady-state experimental conditions:

Integrate the above two formulas to get the first equation:

Rewrite the first equation to get the second equation:

Let A=R _1ρ ·Ts, rewrite the second equation to obtain the deformation formula:

in,

is the unsaturated reference signal under the unsteady experimental condition, I ^app is the saturated signal under the unsteady experimental condition, I ₀ is the unsaturated reference signal under the steady state experimental condition, R _1w is the longitudinal relaxation rate of water, R _1ρ is the spin-lock relaxation rate of water, Ts is the saturation time under unsteady experimental conditions, Td is the recovery time under unsteady experimental conditions, θ is the angle at which the saturation RF pulse flips the magnetization vector of water, e is a natural constant.

Wherein, based on the longitudinal relaxation rate of water and the spin-lock relaxation rate of water, the steps of acquiring the magnetic resonance chemical exchange saturation transfer signal under the steady-state experimental condition specifically include: acquiring the saturation signal and the unsaturated signal under the steady-state experimental condition The ratio formula of the reference signal; when the saturation time is long enough under the preset steady-state experimental conditions, the ratio formula is rewritten to obtain the rewritten ratio formula; based on the rewritten ratio formula, the longitudinal relaxation rate of water and the automatic The spin-lock relaxation rate was calculated to obtain the magnetic resonance chemical exchange saturation transfer signal under steady-state experimental conditions.

The formula for the ratio of the saturated signal to the non-saturated reference signal under steady-state experimental conditions is:

where I is the saturation signal under steady-state experimental conditions.

Wherein, when the saturation time is long enough under the preset steady-state experimental conditions, the steps of rewriting the comparison value formula specifically include: the saturation time under the preset steady-state experimental conditions is infinite, then

The value of is 0, and the rewritten ratio formula is:

Wherein, the longitudinal relaxation rate of water and the spin-lock relaxation rate of water are calculated based on the rewritten ratio formula, and the steps of obtaining the magnetic resonance chemical exchange saturation transfer signal under steady-state experimental conditions specifically include: based on the rewritten ratio formula The ratio formula calculates the longitudinal relaxation rate of water and the spin-lock relaxation rate of water to obtain the ratio of I/I ₀ .

Wherein, the step of acquiring the longitudinal relaxation rate of water specifically includes: acquiring the longitudinal relaxation rate of water based on a conventional magnetic resonance quantitative technology.

Among them, conventional magnetic resonance quantitative technology includes T ₁ mapping technology.

In order to solve the above-mentioned technical problems, another technical solution adopted by the present application is to provide a chemical exchange saturation transfer quantitative device for magnetic resonance, the device comprising: a memory for storing program data, and when the program data is executed, it can realize the following: The steps in the chemical exchange saturation transfer quantitative method for magnetic resonance described in any one of the above; a processor for executing program instructions stored in a memory to realize the chemical exchange for magnetic resonance as described in any of the above Steps in a quantification method for saturation transfer.

In order to solve the above-mentioned technical problems, another technical solution adopted in the present application is to provide a computer-readable storage medium, where a computer program is stored on the computer-readable storage medium. Steps in a quantitative method for chemical exchange saturation transfer for magnetic resonance.

The beneficial effects of the present application are: different from the prior art, the present application can calculate and obtain the steady-state CEST signal based on the non-steady-state CEST signal through a preset deformation formula, remove the influence of imaging parameters on the CEST quantitative result, and solve the problem of non-steady-state CEST signal. Under the condition of steady-state imaging, the CEST effect is underestimated, and the quantitative results are highly dependent on the imaging parameters, which improves the accuracy of CEST quantification; further, the present application can speed up the CEST quantitative accuracy without affecting the Imaging speed, improve the efficiency of imaging research.

【Description of drawings】

In order to illustrate the technical solutions in the embodiments of the present application more clearly, the following briefly introduces the drawings that are used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without creative effort.

1 is a schematic flow diagram of an embodiment of the chemical exchange saturation transfer quantitative method for magnetic resonance in the present application;

Fig. 2 is the sub-flow chart of step S12 in Fig. 1;

Fig. 3 is the sub-flow chart of step S14 in Fig. 1;

4 is a schematic diagram of the comparison of the unsteady CEST signals obtained in Example 1 of the present application and Comparative Example 1 and the corresponding quantitative results of the CEST effect obtained by calculation;

5 is a schematic structural diagram of an embodiment of the chemical exchange saturation transfer quantitative device for magnetic resonance of the present application;

FIG. 6 is a schematic structural diagram of an embodiment of a computer-readable storage medium of the present application.

【Detailed ways】

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of this application.

The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. As used in the examples of this application and the appended claims, the singular forms "a," "the," and "the" are intended to include the plural forms as well, unless the above clearly dictates otherwise, "a plurality of" "Generally includes at least two, but does not exclude the case of including at least one.

It should be understood that the term "and/or" used in this document is only an association relationship to describe the associated objects, indicating that there may be three kinds of relationships, for example, A and/or B, which may indicate that A exists alone, and A and B exist at the same time. B, there are three cases of B alone. In addition, the character "/" in this document generally indicates that the related objects are an "or" relationship.

It should be understood that the terms "comprising", "comprising" or any other variation used herein are intended to encompass a non-exclusive inclusion such that a process, method, article or device comprising a series of elements includes not only those elements, but also Other elements not expressly listed or inherent to such a process, method, article or apparatus are also included. Without further limitation, an element defined by the phrase "comprises" does not preclude the presence of additional identical elements in a process, method, article, or device that includes the element.

Magnetic resonance chemical exchange saturation transfer (CEST) imaging is a magnetic resonance molecular imaging method that can detect the characteristics of the microenvironment of biological tissues, and can measure endogenous metabolites, compounds (such as glucose, glycogen, amide protons, etc.) Derived paramagnetic/diamagnetic CEST contrast agents provide new methods for imaging a variety of diseases (such as stroke, tumor, epilepsy, etc.).

However, the quantification of the CEST effect is very complex and is affected by many factors, which are closely related to important imaging parameters such as saturation time (Ts) and recovery time (Td). In fact, the CEST effect is the superposition of two processes, namely: the signal reduction of the CEST contrast agent due to the saturation effect and the signal recovery of the water molecule through the relaxation process. Sufficient long-term saturation and relaxation recovery are prerequisites for the CEST signal to reach a steady state. However, based on imaging time and safety considerations and limitations of hardware systems, most current CEST imaging studies are usually performed under the condition of short saturation time and recovery time. implemented, that is, the resulting CEST signal is in a non-steady state. This approach leads to an underestimation of the CEST effect, and is not conducive to cross-sectional comparisons and results from studies under different imaging conditions.

Based on the above situation, the present application provides a quantitative method for chemical exchange saturation transfer for magnetic resonance, through a preset deformation formula, the steady-state CEST signal can be obtained by calculating the non-steady-state CEST signal.

The quantitative method for chemical exchange saturation transfer for magnetic resonance provided by this application includes: obtaining the longitudinal relaxation rate of water; presetting a deformation formula based on calculating the spin-lock relaxation rate of water under unsteady experimental conditions, the deformation At least one deformation parameter of the formula is the ratio of the saturated signal and the non-saturated reference signal under the non-steady state experimental conditions; the non-saturated reference signal and the saturated signal, the saturation time and the recovery time under the non-steady state experimental conditions are obtained. The non-saturated reference signal and saturation signal, saturation time and recovery time, and the longitudinal relaxation rate of water under the experimental conditions of the state are calculated and deformed to obtain the spin-lock relaxation rate of water; The spin-lock relaxation rate is used to obtain the magnetic resonance chemical exchange saturation transfer signal under the steady-state experimental condition; the magnetic resonance chemical exchange saturation transfer effect under the steady-state experimental condition is obtained based on the magnetic resonance chemical exchange saturation transfer signal under the steady-state experimental condition.

The present application can calculate and obtain the steady-state CEST signal based on the non-steady-state CEST signal through the preset deformation formula, thereby removing the influence of imaging parameters on the CEST effect and improving the accuracy of CEST quantification; further, the present application can also be used in Under the premise of not affecting the quantitative accuracy of CEST, the imaging speed is accelerated and the imaging research efficiency is improved.

The present application will be described in detail below with reference to the accompanying drawings and embodiments.

Please refer to FIG. 1 , which is a schematic flowchart of an embodiment of the chemical exchange saturation transfer quantitative method for magnetic resonance of the present application. As shown in Figure 1, in this embodiment, the quantitative method includes:

S11: Obtain the longitudinal relaxation rate of water.

In this embodiment, the longitudinal relaxation rate of the water is obtained based on conventional magnetic resonance quantitative technology.

In this embodiment, the longitudinal relaxation rate of water is the inverse of the longitudinal relaxation time of water.

Specifically, the process of the nuclei of water molecules returning from the excited state to the equilibrium arrangement state is called the relaxation process of water, and the time required for it is the relaxation time of water. The relaxation time of water includes the longitudinal relaxation time (T1), and the longitudinal relaxation rate R _1w of water is 1/T1.

In this embodiment, conventional magnetic resonance quantitative techniques include T1mapping techniques.

Specifically, T1mapping is to directly measure the value of T1, and through the value of T1, the longitudinal relaxation rate R _1w of water can be obtained.

S12: Preset a deformation formula for calculating the spin-lock relaxation rate of water under unsteady experimental conditions, and at least one deformation parameter of the deformation formula is a ratio of a saturated signal to a non-saturated reference signal under unsteady experimental conditions.

In this embodiment, the non-steady-state experimental conditions refer to insufficient saturation and recovery conditions, that is, experiments are performed under the conditions of short saturation time and recovery time.

S13: Obtain the non-saturated reference signal and the saturation signal, the saturation time and the recovery time under the non-steady state experimental conditions, and according to the non-saturated reference signal and the saturation signal, the saturation time and the recovery time and the longitudinal direction of the water under the non-steady state experimental conditions The relaxation rate is used to calculate the deformation formula to obtain the spin-lock relaxation rate of water.

In this embodiment, the non-saturated reference signal and the saturated signal, the saturation time and the recovery time under the non-steady state experimental conditions are all data obtained directly in the experiment.

S14: Based on the longitudinal relaxation rate of water and the spin-lock relaxation rate of water, the magnetic resonance chemical exchange saturation transfer signal under steady-state experimental conditions is obtained.

In this embodiment, based on the longitudinal relaxation rate of water, the spin-lock relaxation rate of water, and the angle at which the saturation radio frequency pulse flips the magnetization vector of water, the magnetic resonance chemical exchange saturation transfer signal under steady-state experimental conditions is calculated and obtained.

Among them, the angle θ at which the saturation radio frequency pulse flips the magnetization vector of water is the data obtained directly in the experiment.

S15: Obtain the magnetic resonance chemical exchange saturation transfer effect under the steady state experimental condition based on the magnetic resonance chemical exchange saturation transfer signal under the steady state experimental condition.

Different from the prior art, the present application can calculate and obtain the steady-state CEST signal based on the non-steady-state CEST signal through a preset deformation formula, which solves the problem that the CEST effect is underestimated under non-steady-state imaging conditions, and the quantitative result is highly dependent on imaging. The disadvantages of the parameters improve the accuracy of CEST quantification; further, the present application removes the influence of imaging parameters on the CEST effect, and avoids that the quantitative results are highly dependent on the imaging parameters, so it can be achieved without affecting the quantitative accuracy of CEST. It can speed up the imaging speed and improve the efficiency of imaging research.

Please refer further to FIG. 2 , which is a sub-flow chart of step S12 in FIG. 1 . As shown in FIG. 2 , in this embodiment, a deformation formula for calculating the spin-lock relaxation rate of water under unsteady experimental conditions is preset, and at least one deformation parameter of the deformation formula is saturation under unsteady experimental conditions. The step of the ratio of the signal to the non-saturated reference signal specifically includes:

S21: Obtain the non-saturated reference signal and the calculation formula of the saturated signal under non-steady state experimental conditions.

In this embodiment, the calculation formula of the non-saturated reference signal under non-steady-state experimental conditions is:

The calculation formula of the saturated signal under unsteady experimental conditions is:

in,

Among them, e is an infinite non-repeating decimal with a value between 2.7 and 2.8.

Specifically, the value of e is about 2.718281828.

Among them, the calculation formulas of the non-saturated reference signal and the saturated signal under the non-steady state experimental conditions are the existing formulas.

S22: Integrate the above two formulas to obtain the first equation.

In this embodiment, the calculation formula of the non-saturated reference signal under the non-steady-state experimental condition is rewritten, and the calculation formula of the non-saturated reference signal I ₀ under the steady-state experimental condition can be obtained:

Substitute the calculation formula of the non-saturated reference signal I ₀ under the steady-state experimental condition into the calculation formula of the saturated signal under the non-steady-state experimental condition, and obtain the first equation:

S23: Rewrite the first equation to obtain the second equation.

In this embodiment, the saturated signal I ^app under the unsteady experimental condition in the first equation and the non-saturated reference signal

Moving to the same side, the resulting second equation is:

S24: Rewrite the second equation to obtain a deformation formula; at least one deformation parameter of the deformation formula is a ratio of a saturated signal to a non-saturated reference signal under non-steady state experimental conditions.

In this embodiment, let A=R _1ρ ·Ts, rewrite the second equation to obtain the deformation formula:

It can be seen from the deformation formula that one of the deformation parameters on the left side of the equation of the deformation formula is the saturated signal I ^app and the non-saturated reference signal under the unsteady experimental conditions.

ratio.

In this embodiment, the non-saturated reference signal under non-steady-state experimental conditions

The saturation signal I ^app , the saturation time Ts and the recovery time Td, and the angle θ at which the magnetization vector of the water is flipped by the saturation radio frequency pulse are all directly obtained in the experiment. The longitudinal relaxation rate R _1w of water can be calculated by the T1mapping technique. Therefore, , the only unknown A in the deformation formula can be obtained by fitting these known data, and then the spin-lock relaxation rate R _1ρ of water can be obtained through A.

Please refer to FIG. 3 , which is a sub-flow chart of step S14 in FIG. 1 . As shown in FIG. 3 , in this embodiment, based on the longitudinal relaxation rate of water and the spin-lock relaxation rate of water, the step of acquiring the magnetic resonance chemical exchange saturation transfer signal under steady-state experimental conditions specifically includes:

S31: Obtain the ratio formula of the saturated signal and the non-saturated reference signal under the steady-state experimental condition.

In this embodiment, the formula for the ratio of the saturated signal to the non-saturated reference signal under steady-state experimental conditions is:

where I is the saturation signal under steady-state experimental conditions.

The formula for the ratio of the saturated signal to the non-saturated reference signal under steady-state experimental conditions is an existing formula.

S32: When the saturation time is long enough under the preset steady-state experimental condition, rewrite the ratio formula to obtain the rewritten ratio formula.

In this embodiment, when the saturation time is long enough under the preset steady-state experimental conditions, the saturation time under the preset steady-state experimental conditions can be preset to be infinite, and when Ts is ∞,

is 0, then the rewritten ratio formula obtained is:

S33: Calculate the longitudinal relaxation rate of water and the spin-lock relaxation rate of water based on the rewritten ratio formula, and obtain the magnetic resonance chemical exchange saturation transfer signal under steady-state experimental conditions.

In this embodiment, the longitudinal relaxation rate R _1w of water is calculated by the T ₁ mapping technique, the spin-lock relaxation rate R _1ρ of water is calculated by the deformation formula, and the angle θ at which the saturation radio frequency pulse flips the magnetization vector of water is The data obtained directly in the experiment can therefore be calculated based on the rewritten ratio formula to calculate the longitudinal relaxation rate of water and the spin-lock relaxation rate of water to obtain the ratio of I/I ₀ .

Among them, the ratio of I/I ₀ is the magnetic resonance chemical exchange saturation transfer signal under steady-state experimental conditions.

Different from the prior art, the deformation formula is preset in the present application, and the spin-lock relaxation rate of water can be obtained by calculating the non-saturated reference signal and the saturated signal under non-steady-state experimental conditions, and based on the longitudinal relaxation rate of water and water The spin-lock relaxation rate is obtained, and the magnetic resonance chemical exchange saturation transfer signal under the steady-state experimental condition can be obtained, that is, the application can calculate the steady-state CEST signal based on the unsteady CEST signal, and solve the CEST effect under the unsteady imaging condition. The drawbacks of being underestimated and the quantitative results are highly dependent on imaging parameters improves the accuracy of CEST quantification; further, the present application avoids the high dependence of quantitative results on imaging parameters by removing the influence of imaging parameters on the CEST effect. Therefore, it can speed up the imaging speed and improve the efficiency of imaging research without affecting the quantitative accuracy of CEST.

In order to facilitate the understanding of the embodiments of the present application, the present application provides the following non-limiting examples to further describe the present application in detail.

Example 1

The chemical exchange process of water, semisolid macromolecules, and amide protons (amide) is simulated using the classical three-cell Bloch McConnell equation. Assuming that under the 11.7 Tesla magnetic field environment, the longitudinal relaxation rate of water is 0.5 Hz and the transverse relaxation rate is 30 Hz; the longitudinal relaxation rate of the amide proton is 1 Hz and the transverse relaxation rate is 66.7 Hz; the longitudinal relaxation rate of the semi-solid macromolecule is 1 Hz and the transverse relaxation rate is 1 Hz. Relaxation rate 105Hz. The ratios of amide protons (resonance frequency at 3.5 ppm relative to water) and semisolid macromolecules (resonance frequency at 0 ppm relative to water) relative to water were 0.1% and 13.9%, respectively, corresponding to exchange rates of 30 Hz and 23 Hz. Set the saturation energy amplitude (B1) to 1 μT, the saturation time (Ts)/recovery time (Td) to be 2s/2s and 4s/4s, respectively, and simulate the CEST signal in the range of -4.5 to 4.5ppm with a step size of 0.1ppm. The CEST signal as well as the CEST effect were calculated by the chemical exchange saturation transfer quantitative method for magnetic resonance provided herein.

Comparative Example 1

The chemical exchange process of water, semisolid macromolecules and amide protons (amide) is simulated using the classical three-cell Bloch McConnell equation. Assuming that under the 11.7 Tesla magnetic field environment, the longitudinal relaxation rate of water is 0.5 Hz and the transverse relaxation rate is 30 Hz; the longitudinal relaxation rate of the amide proton is 1 Hz and the transverse relaxation rate is 66.7 Hz; the longitudinal relaxation rate of the semi-solid macromolecule is 1 Hz and the transverse relaxation rate is 1 Hz. Relaxation rate 105Hz. The ratios of amide protons (resonance frequency at 3.5 ppm relative to water) and semisolid macromolecules (resonance frequency at 0 ppm relative to water) relative to water were 0.1% and 13.9%, respectively, corresponding to exchange rates of 30 Hz and 23 Hz. Set the saturation energy amplitude (B1) to 1 μT, the saturation time (Ts)/recovery time (Td) to be 2s/2s and 4s/4s, respectively, and simulate the CEST signal in the range of -4.5 to 4.5ppm with a step size of 0.1ppm. The CEST effect is calculated by a conventional asymmetric analysis method, that is, MTRasym=(I(ω)-I(-ω))/I ₀ , where I is the saturation signal under the steady-state experimental condition, and I ₀ is the steady-state experimental condition The unsaturated reference signal under , ω is the chemical shift relative to the water molecule.

Specifically, please refer to FIG. 4 . FIG. 4 is a comparative schematic diagram of the unsteady CEST signals obtained in Example 1 of the present application and Comparative Example 1 and the corresponding quantitative results of the CEST effect obtained by calculation.

Among them, Figure a) is the unsteady CEST signal obtained by simulation in Comparative Example 1, Figure b) is the corresponding quantitative result of CEST effect calculated by asymmetric analysis method in Comparative Example 1, Ts/Td are 2s/2s respectively and 4s/4s; Figure c) is the steady-state CEST signal obtained by the calculation of the preset formula of the application in the embodiment 1, and Figure d) is the quantitative result of the CEST effect calculated by the algorithm of the application in the embodiment 1. Schematic diagrams when Ts/Td are 2s/2s and 4s/4s, respectively.

It can be seen from Figure 4 that the unsteady CEST signal simulated in Comparative Example 1 is significantly affected by different saturation and recovery times. The signals corresponding to longer saturation time Ts and recovery time Td (4s/4s) are significantly different from those of shorter saturation time. Compared with the signal corresponding to the recovery time Td (2s/2s), the decrease of Ts is more obvious; and when Ts/Td=2s/2s, the CEST effect is 2.6%, and when Ts/Td=4s/4s, the CEST effect The increase was 3.3%, and the difference between the two was obvious, indicating that the quantitative results of CEST were significantly affected by Ts/Td under non-steady-state imaging conditions.

It can also be seen from FIG. 4 that using the algorithm provided by the present application, the CEST signals corresponding to different saturation times and recovery times can be overlapped, indicating that the preset formula of the present application can be used to obtain stable imaging conditions based on non-steady CEST signals. and when Ts/Td=2s/2s and Ts/Td=4s/4s, the corresponding quantitative results of CEST effect are 3.8% and 3.7%, respectively, which are very close, and both are larger than those under non-steady-state conditions. The obtained CEST effect shows that the algorithm provided in this application can remove the influence of imaging parameters such as Ts and Td on CEST quantification, and solves the drawback of underestimated CEST effect under non-steady-state imaging conditions, thereby realizing non-steady-state imaging. Accurate and stable quantification of CEST steady-state signals under conditions. Further, since the present application removes the influence of imaging parameters on the CEST effect, it avoids that the quantitative results are highly dependent on the imaging parameters, and thus can speed up the imaging speed and improve the efficiency of imaging research without affecting the quantitative accuracy of CEST.

Different from the prior art, the present application can calculate and obtain the steady-state CEST signal based on the non-steady-state CEST signal through a preset deformation formula, which solves the problem that the CEST effect is underestimated under non-steady-state imaging conditions, and the quantitative result is highly dependent on imaging. The disadvantages of the parameters improve the accuracy of CEST quantification; further, the present application removes the influence of imaging parameters on the CEST effect, and avoids that the quantitative results are highly dependent on the imaging parameters, so it can be used without affecting the quantitative accuracy of CEST. It can speed up the imaging speed and improve the efficiency of imaging research.

Correspondingly, the present application provides a chemical exchange saturation transfer quantitative device for magnetic resonance.

Please refer to FIG. 5 , which is a schematic structural diagram of an embodiment of the chemical exchange saturation transfer quantitative device for magnetic resonance of the present application. As shown in FIG. 5 , the chemical exchange saturation transfer quantitative device 50 for magnetic resonance includes a processor 51 and a memory 52 coupled to each other.

In this embodiment, the memory 52 is used to store program data, and when the program data is executed, the steps in the chemical exchange saturation transfer quantitative method for magnetic resonance as described in any of the above can be implemented; the processor 51 is used to execute the memory 52 Stored program instructions to implement the steps in any of the above method embodiments or the corresponding steps performed by the chemical exchange saturation transfer quantitative apparatus for magnetic resonance in any of the above method embodiments. In addition to the above-mentioned processor 51 and memory 52, the chemical exchange saturation transfer quantitative device 50 for magnetic resonance may also include a touch screen, a communication circuit, etc. as required, which is not limited herein.

Specifically, the processor 51 is used to control itself and the memory 52 to implement the steps in any of the above-mentioned embodiments of the chemical exchange saturation transfer quantitative method for magnetic resonance. The processor 51 may also be referred to as a CPU (Central Processing Unit, central processing unit). The processor 51 may be an integrated circuit chip with signal processing capability. The processor 51 may also be a general-purpose processor, a digital signal processor (Digital Signal Processor, DSP), an application specific integrated circuit (Application Specific Integrated Circuit, ASIC), a field programmable gate array (Field-Programmable Gate Array, FPGA) or other Programmable logic devices, discrete gate or transistor logic devices, discrete hardware components. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. In addition, the processor 51 may be jointly implemented by a plurality of integrated circuit chips.

Correspondingly, the present application provides a computer-readable storage medium.

Please refer to FIG. 6 , which is a schematic structural diagram of an embodiment of a computer-readable storage medium of the present application.

The computer-readable storage medium 60 includes a computer program 601 stored on the computer-readable storage medium 60. When the computer program 601 is executed by the foregoing processor, the steps in any of the foregoing method embodiments or the steps in the foregoing method embodiments for magnetic resonance are implemented. The chemical exchange saturation transfer quantitative device corresponds to the steps performed.

Specifically, if the integrated units are implemented in the form of software functional units and sold or used as independent products, they may be stored in a computer-readable storage medium 60 . Based on such understanding, the technical solutions of the present application can be embodied in the form of software products in essence, or the parts that contribute to the prior art, or all or part of the technical solutions, which are stored in a computer-readable The storage medium 60 includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) or a processor (processor) to execute all or part of the steps of the methods of the various embodiments of the present application. The aforementioned computer-readable storage medium 50 includes: a USB flash drive, a removable hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, etc. medium of program code.

In the several embodiments provided in this application, it should be understood that the disclosed method and apparatus may be implemented in other manners. For example, the apparatus implementations described above are only illustrative, for example, the division of modules or units is only a logical function division, and there may be other divisions in actual implementation, for example, multiple units or components may be combined or Can be integrated into another system, or some features can be ignored, or not implemented. On the other hand, the shown or discussed mutual coupling or direct coupling or communication connection may be through some interfaces, indirect coupling or communication connection of devices or units, which may be in electrical, mechanical or other forms.

Units described as separate components may or may not be physically separated, and components shown as units may or may not be physical units, that is, may be located in one place, or may be distributed to multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution in this implementation manner.

In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically alone, or two or more units may be integrated into one unit. The above-mentioned integrated units may be implemented in the form of hardware, or may be implemented in the form of software functional units.

The integrated unit, if implemented as a software functional unit and sold or used as a stand-alone product, may be stored in a computer-readable storage medium. Based on this understanding, the technical solutions of the present application can be embodied in the form of software products in essence, or the parts that contribute to the prior art, or all or part of the technical solutions, and the computer software products are stored in a storage medium , including several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) or a processor (processor) to execute all or part of the steps of the methods of the various embodiments of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, Read-Only Memory (ROM, Read-Only Memory), Random Access Memory (RAM, Random Access Memory), magnetic disk or optical disk and other media that can store program codes .

The above description is only an embodiment of the present application, and is not intended to limit the scope of the patent of the present application. Any equivalent structure or equivalent process transformation made by using the contents of the description and drawings of the present application, or directly or indirectly applied to other related technologies Fields are similarly included within the scope of patent protection of this application.

Claims

A chemical exchange saturation transfer quantitative method for magnetic resonance, characterized in that, comprising:

Obtain the longitudinal relaxation rate of water;

Presetting a deformation formula based on the calculation of the spin-lock relaxation rate of water under unsteady experimental conditions, where at least one deformation parameter of the deformation formula is the ratio of the saturated signal to the non-saturated reference signal under the unsteady experimental condition;

Obtain the non-saturated reference signal and the saturation signal, the saturation time and the recovery time under the non-steady state experimental conditions, and according to the non-saturated reference signal and the saturation signal, the saturation time and the recovery time under the non-steady state experimental conditions and the water Calculate the deformation formula for the longitudinal relaxation rate of , and obtain the spin-lock relaxation rate of water;

based on the longitudinal relaxation rate of the water and the spin-lock relaxation rate of the water, obtaining a magnetic resonance chemical exchange saturation transfer signal under steady-state experimental conditions;

The magnetic resonance chemical exchange saturation transfer effect under the steady state experimental condition is obtained based on the magnetic resonance chemical exchange saturation transfer signal under the steady state experimental condition.
The quantitative method according to claim 1, wherein the preset is based on a deformation formula for calculating the spin-lock relaxation rate of water under unsteady experimental conditions, and at least one deformation parameter of the deformation formula is an unsteady The steps of determining the ratio of the saturated signal to the non-saturated reference signal under the experimental conditions specifically include:

Obtain the non-saturated reference signal and the calculation formula of the saturated signal under non-steady-state experimental conditions:

Integrate the above two formulas to get the first equation:

The first equation is rewritten to obtain the second equation:

Let A=R 1ρ ·Ts, rewrite the second equation to obtain the deformation formula:

in,
is the non-saturated reference signal under the non-steady-state experimental condition, I app is the saturated signal under the non-steady-state experimental condition, I 0 is the non-saturated reference signal under the steady-state experimental condition, and R 1w is the water The longitudinal relaxation rate of , R 1ρ is the spin-lock relaxation rate of the water, Ts is the saturation time under the unsteady experimental conditions, Td is the recovery time under the unsteady experimental conditions, and θ is The angle at which the saturation RF pulse flips the magnetization vector of water, e is a natural constant.
The quantitative method according to claim 2, wherein the magnetic resonance chemical exchange saturation transfer under steady-state experimental conditions is obtained based on the longitudinal relaxation rate of the water and the spin-lock relaxation rate of the water The steps of the signal include:

Obtain the ratio formula of the saturated signal and the non-saturated reference signal under steady-state experimental conditions;

When the saturation time is long enough under the preset steady-state experimental conditions, rewrite the ratio formula to obtain the rewritten ratio formula;

Based on the rewritten ratio formula, the longitudinal relaxation rate of the water and the spin-lock relaxation rate of the water are calculated, and the magnetic resonance chemical exchange saturation transfer signal under the steady state experimental condition is obtained.
The quantitative method according to claim 3, wherein the formula for the ratio of the saturated signal to the non-saturated reference signal under the steady-state experimental condition is:

Wherein, I is the saturation signal under the steady state experimental conditions.
The quantitative method according to claim 4, wherein when the saturation time is long enough under the preset steady-state experimental conditions, the step of rewriting the ratio formula specifically includes:

Assuming that the saturation time under the steady state experimental conditions is infinite, then
is 0, and the rewritten ratio formula is:
The quantitative method according to claim 5, wherein the longitudinal relaxation rate of the water and the spin-lock relaxation rate of the water are calculated based on the rewritten ratio formula, and the obtained The steps of the magnetic resonance chemical exchange saturation transfer signal under steady state experimental conditions specifically include:

Based on the rewritten ratio formula, the longitudinal relaxation rate of the water and the spin-lock relaxation rate of the water are calculated to obtain the ratio of I/I 0 .
The quantitative method according to claim 1, wherein the step of obtaining the longitudinal relaxation rate of water specifically comprises:

The longitudinal relaxation rate of the water is obtained based on conventional magnetic resonance quantitative techniques.
The quantitative method according to claim 7, wherein the conventional magnetic resonance quantitative technique comprises a T 1 mapping technique.
A chemical exchange saturation transfer quantitative device for magnetic resonance, characterized in that, comprising:

a memory for storing program data, which implements the steps in the quantitative method according to any one of claims 1 to 8 when the stored program data is executed;

A processor for executing program instructions stored in the memory to implement steps in the quantitative method according to any one of claims 1 to 8.
A computer-readable storage medium, characterized in that, a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the quantitative method according to any one of claims 1 to 8 is implemented. A step of.