Method and apparatus for quantitative magnetic resonance imaging using spin-lock radio frequency trains

Abstract

A method, apparatus, and non-transitory computer-readable storage medium for quantitative magnetic resonance imaging (MRI) are provided. In the method, a first magnetization signal is obtained based on a first set of spin-locks (102). Additionally, a second magnetization signal is obtained based on a second set of spin-locks (103). A final magnetization is obtained based on the first magnetization signal and the second magnetization signal (104). The above process is repeated to collect one or more final magnetization signals for quantification of tissue parameters.

Description

[0001] This application is based upon and claims the benefit of priority of provisional application No. 63 / 326,766, filed on April 1, 2022, the entire contents of which are incorporated by reference for all effects. Technical Field

[0002] The present disclosure relates to the field of magnetic resonance imaging (MRI) system imaging, and more particularly, to a method and apparatus for quantitative magnetic resonance imaging using a spin-lock radio frequency tandem. Background Art

[0003] MRI is one of the most widely used non-invasive imaging modalities in clinical diagnosis. In recent years, its ability to detect diseases at the molecular level has attracted increasing interest in both clinical and research settings. In the field of MRI, two types of molecular signals are widely studied, namely chemical exchange (CE) and magnetization transfer (MT).

[0004] In general, off-resonance saturation radio frequency (RF) pulses are often used to study CE and MT based contrast. It is mainly based on the exchange or transfer of saturated biomolecular protons or macromolecular bonded water protons with free water protons, which are saturated by selective off-resonance RF pulses. This effect leads to the attenuation of the water signal, which allows the indirect measurement of CE and MT signals.

[0005] In addition, spin-lock-based techniques can also be used to measure CE and MT signals. Spin locking is achieved by applying radio frequency (RF) pulses to the magnetization to align the magnetization along the effective spin-locking field. The resulting MR signal is measured with a time constant T 1ρ decay, the time constant T 1ρ is related to the amplitude of the effective spin lock field which depends on the amplitude of the spin lock pulse (γB1 / 2π) and the resonant frequency shift of the spin lock pulse.

[0006] In general, the duration and amplitude of a spin-lock RF pulse are key parameters for spin-lock based techniques. They play an important role in the assessment of the biochemical properties of tissues. However, the maximum duration of a spin-lock RF pulse is limited by the hardware and specific absorption rate (SAR) of the MRI system. Using a train of spin-lock pulses with a shorter duration of each RF pulse can be used to alleviate this problem. However, it is worth noting that unlike a single spin-lock pulse, the relaxation model using a train of spin-lock RF pulses is very complex, and the traditional single exponential model cannot be used for quantification in this case. This poses a huge challenge for quantification when a train of spin-lock RF pulses is used. Summary of the invention

[0007] Examples of the present disclosure provide methods and apparatus for quantitative magnetic resonance imaging using a spin-lock radio frequency tandem.

[0008] According to a first aspect of the present application, a method for quantitative magnetic resonance imaging is provided, comprising: obtaining a first magnetization signal based on a first group of spin lock modules, obtaining a second magnetization signal based on a second group of spin lock modules, and obtaining a final magnetization signal based on the first magnetization signal and the second magnetization signal.

[0009] According to a second aspect of the present application, a device for quantitative magnetic resonance imaging is provided. The device includes one or more processors and a memory configured to store instructions executed by the one or more processors. In addition, when executing the instructions, the one or more processors are configured to perform actions, including the following steps: obtaining a first magnetization signal based on a first group of spin lock modules, obtaining a second magnetization signal based on a second group of spin lock modules, and obtaining a final magnetization signal based on the first magnetization signal and the second magnetization signal.

[0010] According to a third aspect of the present application, a non-transitory computer-readable storage medium is provided. The medium stores computer-executable instructions, and when executed by one or more computer processors, the one or more computer processors perform actions including the following steps: obtaining a first magnetization signal based on a first group of spin lock modules, obtaining a second magnetization signal based on a second group of spin lock modules, and obtaining a final magnetization signal based on the first magnetization signal and the second magnetization signal.

[0011] One or more final magnetizations are obtained by repeating the above process and used for quantification of one or more tissue parameters.

[0012] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not intended to restrict the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate examples consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0014] Figure 1 is a flow chart showing a method for quantitative magnetic resonance imaging using a spin lock radio frequency tandem according to some examples of the present application.

[0015] Figure 2 Detailed description is given of a magnetic resonance imaging system according to some examples of the present application.

[0016] Figure 3 Detailed description is given of a pulse train including a plurality of repetitive spin lock modules according to some examples of the present application. DETAILED DESCRIPTION

[0017] Reference will now be made in detail to example embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, wherein the same reference numerals in different drawings represent the same or similar elements unless otherwise specified. The implementations described in the following preferred embodiments do not represent all implementations consistent with the present invention. Instead, they are merely examples of devices and methods consistent with the aspects related to the disclosure recorded in the appended claims.

[0018] The terms used in this disclosure are only used to describe specific embodiments and are not intended to limit the disclosure. As used in this disclosure and the appended claims, the singular forms "a", "an", and "the" also include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein is intended to represent and include any or all possible combinations of one or more of the associated listed items.

[0019] It should be understood that although the terms "first", "second", "third", etc. may be used herein to describe various information, such information should not be limited by these terms. These terms are only used to distinguish one type of information from another type of information. For example, without departing from the scope of the present disclosure, the first information may be referred to as the second information; similarly, the second information may also be referred to as the first information. As used herein, the term "if" may be understood to mean "when" or "at" or "in response to a judgment" depending on the context.

[0020] References throughout the specification to "one embodiment," "an embodiment," "an example," "some embodiments," "some examples," or similar language mean that the particular features, structures, or characteristics being described are included in at least one embodiment or embodiments. Unless explicitly stated otherwise, features, structures, elements, or characteristics described in conjunction with one or some embodiments are also applicable to other embodiments.

[0021] In order to facilitate understanding by those skilled in the art, a variety of implementation methods are listed in the embodiments of the present invention so as to clearly describe the technical solutions of the embodiments of the present invention. Of course, those skilled in the art can understand that the multiple embodiments provided in the embodiments of the present invention can be performed independently, or can be performed in combination with the methods of other embodiments in the embodiments of the present invention, or can be performed independently, or can be performed in combination with some methods in other related technologies. The embodiments of the present invention are not limited to this.

[0022] The present disclosure provides a method for simplifying T using a spin lock radio frequency cascade. 1ρMethods and apparatus for quantification. In addition, the present disclosure provides methods and apparatus for quantifying tissue parameters related to magnetization transfer using a spin lock radio frequency train based on off-resonance spin locks. A spin lock radio frequency train is a nuclear magnetic resonance pulse train used to manipulate the magnetization intensity of protons in the body. The spin lock radio frequency train can be composed of a series of spin lock modules using a specified frequency and duration.

[0023] In some examples according to the present disclosure, a pulse train of a spin lock module train may include multiple spin lock modules. In a spin lock RF train, a spin lock module may include a set of RF pulses that are applied to tissue in a specific pattern to create a spin lock field. Spin lock is a specialized magnetic resonance imaging technique for manipulating spins through RF pulses. The technique is particularly useful for studying various molecular scale interactions, measuring relaxation rates, and studying tissue properties.

[0024] For example, a spin lock module can be composed of a spin lock RF cluster, followed by an idle time without RF radiation of duration Td. The spin lock RF cluster includes a spin lock RF pulse with a spin lock time (TSL), which is sandwiched between a head end RF pulse and a tail end RF pulse, wherein the head end RF pulse can be a RF pulse before the spin lock RF pulse, and the tail end RF pulse can be a RF pulse after the spin lock RF pulse. A spoiler gradient can be added after each spin lock RF cluster to dephase the transverse magnetization. The parameters of each spin lock module, including but not limited to the spin lock time, duration, phase of the RF pulse, direction of the spin lock field, and spoiler gradient area, can vary for different spin lock modules.

[0025] Figure 3 Some examples of pulse trains including multiple spin lock modules according to the present disclosure are shown. Figure 3 As shown, the pulse train 300 includes a plurality of spin lock modules 1-n, where n is the number of spin lock modules. Except for the last spin lock module n, at least one spin lock module includes a spin lock RF cluster, followed by an idle time without RF radiation of duration Td. The spin lock RF cluster includes a spin lock RF pulse of duration TSL, a head RF pulse and a tail RF pulse, wherein the spin lock RF pulse is located between the head RF pulse and the tail RF pulse. Figure 3 As shown, the amplitude of the spin lock RF pulse is represented by the frequency of the spin lock (FSL), and the resonant frequency offset of the spin lock RF pulse is represented by the frequency offset (FO). Figure 3 The spin lock module n shown includes a leading RF pulse, a spin lock RF pulse with a TSL duration, and a trailing RF pulse, wherein the spin lock RF pulse is located between the leading end and the trailing end of the RF pulse.

[0026] For a spin lock module with a constant spin lock RF pulse of duration TSL, the magnetization M at the end of the spin lock module can be expressed by the following equation (1): Among them, M ini is the initial magnetization intensity after the head RF pulse and before the spin lock RF pulse in the first spin lock module in the spin lock RF series; R 1ρ (=1 / T 1ρ ) is the spin lattice relaxation rate in the rotating coordinate system; M ss is the steady-state magnetization. Compared with a single spin lock module, having multiple spin lock modules in series can achieve a longer total spin lock time. In the case of two or more spin lock modules in series, the magnetization at the end of the spin lock module series (expressed as M) can be derived using equation (2) and the T1 relaxation during the idle time Td. sl_train_1 ): Where R1 (=1 / T1) is the tissue spin lattice relaxation rate, n is the number of spin lock modules in the spin lock series, and M0 is the equilibrium magnetization intensity. n-1 is a recursive formula And is defined as n≥2.

[0027] In some examples of the present disclosure, different initial magnetizations M are used. ini2 But the same steady-state magnetization M ss The second magnetization signal is acquired. The magnetization intensity M at the end of the spin lock series in the second acquisition sl_train_2 Based on formula (3), we can get the following:

[0028] M ini The modification can be performed by, but not limited to, the following methods: In some examples, the spin lock RF train is performed after longitudinal and / or transverse relaxation (T1 and / or T2) of different lengths of time. Therefore, different degrees of magnetization relaxation will lead to different results.

[0029] In some other examples, the properties of the head RF pulse of the first spin lock module in the series are manipulated to change the M ini . These properties can include phase, frequency modulation, duration, amplitude, etc.

[0030] In some other examples, one or more RF pulses may be used prior to the spin lock RF train to change M ini The radio frequency pulses can have any flip angle, phase, frequency modulation, duration, amplitude, etc. After these radio frequency pulses, spoiler gradients can be applied.

[0031] By subtracting Eq. (2) from Eq. (3), or vice versa, the magnetization equation can be reduced essentially to a simple single exponential model that allows for convenient quantification of R 1ρ (=1 / T 1ρ ):

[0032] In some examples, the term Therefore, by collecting M with different TSL fin , you can use M fin Fit to a single exponential model to obtain R 1ρ .

[0033] In some examples, the spin lock RF pulse train can be applied in a resonant or non-resonant manner. For resonance, the spin lock RF pulse is tuned to the resonant Larmor frequency, and the magnetization is spin locked in the transverse plane. For non-resonant spin lock, the spin lock RF pulse is tuned to a resonant frequency offset Δω from the resonant Larmor frequency, and the magnetization is spin locked at an angle to the transverse plane determined by Δω and the spin lock RF amplitude ω1. The present invention can be used for R in both resonant spin lock and non-resonant spin lock. 1ρ quantification.

[0034] According to the present disclosure, by using a series of non-resonant spin-lock RF modules, the use of spin-lock RF pulse trains for quantitative MRI can also be used to quantify tissue parameters related to magnetization transfer. ini The data can be obtained as shown in formula (4): fin .

[0035] In some examples, the acquired signal is correlated to a specific tissue parameter related to magnetization transfer, such as the macromolecular proton fraction (MPF, also called bound pool fraction (BPF) or other terms), by adjusting the MRI pulse train parameters of the spin-lock RF pulse train and comparing it to other tissue parameters related to magnetization transfer.

[0036] In some examples, the pulse train parameters of each individual spin lock module in the train of spin lock modules may be varied while collecting the magnetization signal. These pulse train parameters include, but are not limited to, TSL, Td, spoiler gradient area, direction of the spin lock field, etc. Machine learning or deep learning may be used to quantify data acquired using spin lock RF pulse trains with different parameters.

[0037] In some examples, the data sets of Δω and ω1 can be collected in various ways and are described as follows. Δω is the resonant frequency offset of the spin lock, and ω1 is the amplitude of the spin lock RF pulse. For example, as shown in equation (4), M fin The first image is created by using a The spin lock pulse train is used to obtain it.

[0038] Similarly, by using a feature ( The spin lock pulse train is connected with M fin The same method as the first image is used to obtain M as shown in equation (4) fin The second image.

[0039] In addition, we can also obtain M as shown in formula (4): fin By using a third or more images having The spin lock pulse train, where i = 3, 4 ... N, N is as shown in formula (4) fin The total number of images. Among them, M fin,1 and M fin,2 M fin The first image and the second image. mpfsl Insensitive to the tissue parameters of the pool. mpfsl In cases where the macromolecular proton fraction (MPF) is more sensitive than other tissue parameters related to magnetization transfer, or under the assumption that other tissue parameters are nearly constant, the Bloch-McConnell equation can be used to calculate the value of R from mpfsl Calculate MPF, either through machine learning or deep learning methods. mpfsl can be different at different Δω, ω1, and / or The value of is obtained and can be used to calculate one or more tissue parameters related to magnetization transfer.

[0041] Furthermore, the magnetization obtained by the spin-lock RF cascade can be fed into machine learning or deep learning algorithms to directly obtain tissue parameters, which may provide important information for tissue characterization.

[0042] Figure 1 is a flow chart illustrating a method for quantitative magnetic resonance imaging using a spin-lock radio frequency tandem according to some examples of the present disclosure.

[0043] In step 101, a target object is arranged in a magnetic resonance imaging system or device. For example, as discussed below Figure 2 As shown, a patient is positioned within a magnetic resonance imaging system 200 .

[0044] In step 102, a first MR image is obtained. For example, step 102 may include multiple steps 102-1, 102-2, and 102-3. In step 102-1, zero, one, or more preparation sequences are implemented. In 102-1, a magnetization reset module is first applied. The module is used to reset the magnetization intensity to zero or a non-zero value. Suppression of blood signals, body fluid signals, or fat signals may also be included in step 102-1.

[0045] In step 102-2, a first set of spin-lock radio frequency is applied. In step 102-2, a fat suppression module may also be included and applied after the spin-lock radio frequency series.

[0046] In step 102 - 3 , a first magnetization signal is acquired.

[0047] After step 102 , a second MR image is acquired in step 103 .

[0048] In step 103, a second magnetization signal corresponding to a second MR image is obtained based on a second initial magnetization and a steady-state magnetization, wherein the second initial magnetization is different from the first initial magnetization used in obtaining the first magnetization, and the steady-state magnetization is the same as the first magnetization used in obtaining the first magnetization. In some examples, the initial magnetization can be modified by at least one of the following steps, but not limited to: using a different relaxation duration before the spin lock radio frequency train, changing the phase, frequency modulation, duration, or amplitude in the first spin lock module of the spin lock radio frequency train; changing the direction of the effective spin lock field; or applying one or more radio frequency pulses with arbitrary flip angles, phases, frequency modulations, durations, or amplitudes before the spin lock radio frequency train.

[0049] For example, step 103 may include multiple steps 103-1, 103-2, and 103-3. In step 103-1, zero, one, or more preparation sequences are implemented. In step 103-1, a magnetization reset module is first applied. The module is used to reset the magnetization intensity to zero or a non-zero value. Suppression of blood signals, body fluid signals, or fat signals may also be included in 103-1.

[0050] In step 103-2, a second set of spin-lock radio frequency modules is applied. In step 103-2, a fat suppression module may also be added and applied after the spin-lock module. In step 103-3, a second magnetization signal is acquired. As described above, the second magnetization signal is acquired with an initial magnetization different from that when the first image is acquired but with the same steady-state magnetization as when the first image is acquired.

[0051] In some examples, step 102 and step 103 are interchangeable. For example, the order of performing step 102 and step 103 can be changed, and step 102 can be performed before or after step 103.

[0052] In step 104 , a final magnetization signal is obtained based on the first magnetization signal obtained in step 102 and the second magnetization signal obtained in step 103 .

[0053] In some examples, after obtaining the final magnetization signal using different acquisition parameters including but not limited to TSL, Td, spin lock amplitude, and spin lock frequency offset in step 104, steps 102, 103, and 104 may be repeatedly performed. After repeatedly performing steps 102, 103, and 104, a desired number of final magnetization signals M may be obtained. fin The desired number of final magnetization signals M can be obtained based on fin In some examples, based on an M obtained as above, s1_train_1 and an M s1_train_2 To calculate a final magnetization signal M fin Two or more final magnetization signals M may be obtained under different acquisition parameters used in steps 102 and 103. fin The final magnetization signal M fin The expected number and quantification method are flexible.

[0054] According to an example of the present disclosure, when a set of spin lock modules is used, the spin relaxation rate can be calculated from the exponential relaxation model by fixing Td as a constant It is also possible to calculate R simultaneously by changing TSL and Td 1p and R1, where R1 represents the longitudinal relaxation rate. The present disclosure is applicable to a single R in a single exponential relaxation model 1p , two R in the double exponential relaxation model 1p or more than two R in a multi-exponential relaxation model 1p quantification.

[0055] R 1p The value can also be directly calculated by machine learning or deep learning, using the first magnetization signal from step 102, the second magnetization signal from step 103, and their repetitions acquired at different acquisition parameters, without calculating M fin .

[0056] In some examples, steps 102 and 103 may be repeated to obtain magnetization signals at different resonant frequency offsets Δω and spin lock RF amplitudes ω1 used in the spin lock RF train. The magnetization signals obtained in steps 102 and 103 may be used to calculate M based on tissue parameters associated with magnetization transfer.fin In addition, one or more R mpfs1 Can be used to obtain one or more tissue parameters related to magnetization transfer.

[0057] In some examples, various magnetizations at different resonant frequency offsets Δω and spin lock RF amplitudes ω1 used in the spin lock RF train obtained at steps 102 and 103 can be directly fed to algorithms in machine learning and deep learning and output one or more tissue parameters related to magnetization transfer.

[0058] In some examples, the sensitivity of the signal to tissue parameters associated with magnetization transfer can be adjusted by adjusting pulse train parameters of the first set of spin lock modules and the second set of spin lock modules.

[0059] The method for quantization using a spin-lock RF cascade according to the above example of the present disclosure can be used as follows: Figure 2 The magnetic resonance imaging system 200 shown in the figure is performed. The magnetic resonance imaging system 200 includes an operator workstation 202, which generally includes a display 204, one or more input devices 206, and a processor 208, the input device 206 being, for example, a keyboard and a mouse. The processor 208 may include a commercially available programmable machine running a commercially available operating system. The operator workstation 202 provides an operator interface that enables a scan prescription to be input into the magnetic resonance imaging system 200. Typically, the operator workstation 202 may be coupled to four servers: a pulse train server 110, a data acquisition server 212, a data processing server 214, and a data storage server 216. The operator workstation 202 and each server 210, 212, 214, and 216 are connected to communicate with each other. For example, the servers 210, 212, 214, and 216 may be connected via a communication system 217, which may include any suitable network connection, whether wired, wireless, or a combination of both. As examples, the communication system 217 may include proprietary or dedicated networks, as well as open networks such as the Internet.

[0060] The pulse train server 210 operates in response to instructions downloaded from the operator workstation 202 to operate the gradient system 218 and the radio frequency system 120. The gradient waveforms required to perform a specified scan are generated and applied to the gradient system 218, the gradient coils in the assembly 122 are excited to generate magnetic field gradients, and are used to position encode the magnetic resonance signals. The gradient coil assembly 122 forms part of the magnet assembly 224, which includes a polarizing magnet 226 and a body radio frequency coil 228.

[0061] The RF system 220 applies the RF waveform to the RF coil 228 or a separate local coil ( Figure 2) to perform a prescribed magnetic resonance pulse train. The RF coil 228 or a separate local coil ( Figure 2 The responsive magnetic resonance signals detected by the radio frequency system 220 (not shown) are received by the radio frequency system 220, where they are amplified, demodulated, filtered and digitized under the guidance of the commands generated by the radio frequency system 220. The radio frequency system 220 includes a radio frequency transmitter for generating various radio frequency pulses used in the magnetic resonance pulse train. The radio frequency transmitter responds to the scanning method and direction from the pulse train server 210 to generate radio frequency pulses of the required frequency, phase and pulse amplitude waveform. The generated radio frequency pulses can be applied to the body radio frequency coil 228 or to one or more local coils or coil arrays ( Figure 2 2. The drive field generator 240 is used to generate the required electromagnetic drive field. For example, the drive field generator may include an external solenoid or a shielded solenoid driven at a low frequency by a large amplifier. In some examples, an additional gradient amplifier may be used to drive the drive field generator.

[0062] The RF system 220 also includes one or more RF receiver channels. Each RF receiver channel includes an RF preamplifier and a detector, wherein the RF preamplifier amplifies the magnetic resonance signal received by the coil 228 connected thereto, and the detector detects and digitizes the I and Q quadrature components of the received magnetic resonance signal. Therefore, the amplitude of the received magnetic resonance signal can be determined at any sampling point by the square root of the sum of the squares of the I and Q components: And the phase of the received magnetic resonance signal can also be determined according to the following relationship:

[0063] Pulse train server 210 also optionally receives patient data from physiological acquisition controller 230. In some examples, physiological acquisition controller 230 may receive signals from a plurality of different sensors connected to the patient, such as electrocardiograph ("ECG") signals from electrodes, or respiration signals from a respiratory bellows or other respiratory monitoring device. These signals are typically used by pulse train server 210 to synchronize or "gate" the execution of a scan with the subject's heartbeat or respiration.

[0064] The pulse train server 210 is also connected to the scan room interface circuit 132, which receives signals from various sensors associated with the condition of the patient and the magnet system. The patient positioning system 234 also receives commands through the scan room interface circuit 232 to move the patient to a desired position during scanning.

[0065] The digitized magnetic resonance signal samples generated by the RF system 220 are received by the data acquisition server 212. The data acquisition server 212 operates in response to instructions downloaded from the operator workstation 202 to receive real-time magnetic resonance data and provide buffer storage so that data is not lost due to data overflow. In some scans, the data acquisition server 212 simply passes the acquired magnetic resonance data to the data processor server 214. However, in scans where information derived from the acquired magnetic resonance data is needed to control further execution of the scan, the data acquisition server 212 is programmed to generate such information and transmit it to the pulse train server 210. For example, during a pre-scan, magnetic resonance data is acquired and used to calibrate the pulse train executed by the pulse train server 210. As another embodiment, the navigator signal can be acquired and used to adjust the operating parameters of the RF system 220 or the gradient system 218, or to control the order of views in which k-space is sampled. In yet another embodiment, the data acquisition server 212 can also be used to process magnetic resonance signals used to detect the arrival of contrast agent in a magnetic resonance angiography (MRA) scan. In all of these examples, the data acquisition server 212 acquires the magnetic resonance data and processes it in real time to generate information for controlling the scan.

[0066] The data processing server 214 receives the magnetic resonance data from the data acquisition server 212 and processes it according to instructions downloaded from the operator workstation 202. For example, such processing may include one or more of the following: reconstructing a two-dimensional or three-dimensional image by performing a Fourier transform on the raw k-space data; performing other image reconstruction algorithms, such as iterative or back-projection reconstruction algorithms; applying filters to the raw k-space data or the reconstructed image; generating functional magnetic resonance images; calculating motion or flow images; and the like.

[0067] The images reconstructed by the data processing server 214 are transmitted back to the operator workstation 202 where they are stored. The real-time images are stored in the database memory cache ( Figure 2 202 ), these images can be output from the database to an operator display 212 or a display 136 located near the magnet assembly 224 for use by the attending physician. Batch mode images or selected real-time images are stored in a host database on disk storage 138. When these images have been reconstructed and transferred to storage, the data processing server 214 notifies the data storage server 216 on the operator workstation 202. The operator can use the operator workstation 202 to archive the images, make films, or send the images to other facilities over the network.

[0068] The magnetic resonance imaging system 200 may also include one or more networked workstations 142. For example, the networked workstation 242 may include a display 244; one or more input devices 246, such as a keyboard and a mouse, and a processor 248. The networked workstation 242 may be located in the same facility as the operator workstation 202, or in a different facility, such as a different medical institution or clinic.

[0069] Whether in the same facility as the operator workstation 202 or in a different facility, a networked workstation 242 can obtain remote access to the data processing server 214 or the data storage server 216 via the communication system 217. Thus, multiple networked workstations 242 can access the data processing server 214 and the data storage server 216. In this way, magnetic resonance data, reconstructed images, or other data can be exchanged between the data processing server 214 or the data storage server 216 and the networked workstation 142 so that the data or images can be processed remotely by the networked workstation 242. The data can be exchanged in any suitable format, such as according to the Transmission Control Protocol (TCP), Internet Protocol (IP), or other known or suitable protocols.

[0070] In some examples, a device for quantitative magnetic resonance imaging is also provided, such as the magnetic resonance imaging system 200. The device may include one or more processors and a memory configured to store instructions executable by the one or more processors. In addition, the one or more processors are configured to perform actions when executing the instructions, including: obtaining a first magnetization signal based on a first group of spin locks, obtaining a second magnetization signal based on a second group of spin locks, and obtaining a final magnetization signal based on the first magnetization signal and the second magnetization signal.

[0071] In some examples, each of the first group of spin locks and the second group of spin locks includes a series of spin lock RF clusters, each spin lock RF pulse cluster is followed by an idle time without RF radiation of duration Td, wherein the spin lock RF cluster may include a spin lock RF pulse of duration TSL, a leading RF pulse, and a trailing RF pulse, wherein the spin lock RF pulse is located between the leading RF pulse and the trailing RF pulse. For example, the first group of spin locks and the second group of spin locks may be respectively as follows: Figure 3 shown.

[0072] In some examples, the duration of TSL, the duration of Td, and the direction of the spin lock field may be different in each spin lock module.

[0073] In some examples, the one or more processors may also repeat the steps of obtaining the first magnetization signal and the second magnetization signal to obtain one or more final magnetization signals. Figure 1As shown, step 102 , step 103 and step 104 may be repeated as many times as desired to obtain a plurality of final magnetization signals.

[0074] In some examples, the one or more processors may also perform quantization based on all final magnetization signals obtained after repeating the steps of obtaining the first magnetization signal and the second magnetization signal.

[0075] In some examples, the one or more processors may also obtain one or more final magnetization signals for different resonant frequency offsets and spin lock RF amplitudes used in a set of spin lock modules. The magnetization signals may be used to calculate tissue parameters related to magnetization transfer based on the Bloch-McConnell equation. In some embodiments, the one or more processors may also feed all final magnetization signals into an artificial intelligence system, such as a machine learning or deep learning system, and output one or more tissue parameters related to magnetization transfer.

[0076] The above method can be implemented using a device including one or more circuits, including an application specific integrated circuit (ASIC), a digital signal processor (DSP), a digital signal processing device (DSPD), a programmable logic device (PLD), a field programmable gate array (FPGA), a controller, a microcontroller, a microprocessor or other electronic components. The device can use circuits combined with other hardware or software components to perform the above method. Each module, submodule, unit or subunit disclosed above can be implemented at least in part using one or more circuits.

[0077] Other examples of the present disclosure will be apparent to those skilled in the art by considering the specification and prior art disclosed herein. This application is intended to cover any variation, use or modification of the present disclosure in accordance with its general principles, and includes differences from the present disclosure within the known or customary range in the art. The specification and examples are intended to be considered as exemplary only.

[0078] It will be understood that the present disclosure is not limited to the exact examples described above and shown in the accompanying drawings, and that various modifications and changes may be made without departing from the scope thereof.

Claims

1. A method for quantitative magnetic resonance imaging, characterized in that include: Obtaining a first magnetization signal based on the first group of spin lock modules; obtaining a second magnetization signal based on the second group of spin lock modules; as well as A final magnetization signal is obtained based on the first magnetization signal and the second magnetization signal.

2. The method according to claim 1, characterized in that: At least one spinlock module of the first group of spinlock modules and the second group of spinlock modules includes a spinlock RF cluster and an idle time without RF radiation having a duration Td after the spinlock RF cluster.

3. The method according to claim 2, characterized in that The spin lock RF cluster includes a head RF pulse, a tail RF pulse, a spin lock RF pulse having a duration of a spin lock time TSL, an amplitude and a resonant frequency offset of the spin lock RF pulse, the spin lock RF pulse is located between the head RF pulse and the tail RF pulse, and a spoiler gradient follows the tail RF pulse.

4. The method according to claim 1, characterized in that: Also includes: The first group of spin lock modules and the second group of spin lock modules having different initial magnetization intensities are obtained.

5. The method according to claim 4, characterized in that Also includes: The initial magnetization is modified by at least one of the following steps: Using different relaxation durations before the spin-lock RF train; as well as Changing the phase, frequency modulation, duration or amplitude of the head end RF pulse in the first spin lock module of the spin lock RF series; or One or more RF pulses with arbitrary flip angle, phase, frequency modulation, duration or amplitude are applied in front of the spin lock RF train.

6. The method according to claim 3, characterized in that The pulse train parameters in each spin lock module in the first group of spin lock modules and the second group of spin lock modules are the same or different, wherein the pulse train parameters include at least one of the following parameters: the duration of the spin lock time, the amplitude of the spin lock radio frequency pulse, the resonant frequency offset of the spin lock radio frequency pulse, the duration of Td, the spoiler gradient area or the direction of the spin lock field.

7. The method according to claim 3, characterized in that Also includes: One or more final magnetization signals are obtained by repeating the steps of obtaining the first magnetization signal and the second magnetization signal, wherein the duration of TSL or the duration of Td during the repetition is different from the duration of TSL or the duration of Td used to obtain the first magnetization signal or the second magnetization signal.

8. The method according to claim 7, characterized in that Also includes: The identification is performed based on all final magnetization signals obtained after repeating the steps of obtaining the first magnetization signal and the second magnetization signal.

9. The method according to claim 3, characterized in that: Also includes: All final magnetization signals under different resonance frequency offsets and amplitudes of spin lock radio frequency pulses in the first group of spin lock modules and the second group of spin lock modules are obtained, wherein all final magnetization signals include the final magnetization signal obtained based on the first magnetization signal and the second magnetization signal and one or more final magnetization signals obtained in the step of repeatedly obtaining the first magnetization signal and the second magnetization signal.

10. The method according to claim 9, characterized in that Also includes: Input all resulting magnetization signals into a machine learning or artificial intelligence system and output one or more tissue parameters associated with the magnetization transfer, or The Bloch-McConnell equation is used to calculate one or more tissue parameters associated with the magnetization transfer from all resulting magnetization signals.

11. The method according to claim 9, characterized in that Also includes: The sensitivity of the signal to the tissue parameter related to magnetization transfer is adjusted by adjusting the pulse train parameters of the first group of spin lock modules and the second group of spin lock modules.

12. An apparatus for quantitative magnetic resonance imaging, characterized in that include: one or more processors; as well as a memory configured to store instructions executable by one or more processors; Wherein, one or more processors are configured to perform the method according to any one of claims 1-11 when executing the instructions.

13. A non-transitory computer-readable storage medium, characterized in that: Used to store computer executable instructions, which, when executed by one or more computer processors, cause one or more of the computer processors to perform the method according to any one of claims 1 to 11.

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