WO2023226115A1

WO2023226115A1 - Method for measuring intrinsic time domain stability parameter of radio frequency receiving coil in fmri

Info

Publication number: WO2023226115A1
Application number: PCT/CN2022/099606
Authority: WO
Inventors: 高阳; 张孝通; 全枝艳
Original assignee: 浙江大学
Priority date: 2022-05-27
Filing date: 2022-06-17
Publication date: 2023-11-30
Also published as: CN114879107A; CN114879107B

Abstract

A method for measuring an intrinsic time domain stability parameter of a radio frequency receiving coil in functional magnetic resonance imaging (FMRI), comprising: respectively inserting dielectrics having different thicknesses between the radio frequency receiving coil and a tested simulation phantom to change the distance between the coil and the phantom, so as to simulate the relative motion between the coil and the phantom (S101); acquiring a plurality of echo EPI images of the tested simulation phantom when the dielectrics having different thicknesses are inserted, and performing processing and reconstruction to obtain intrinsic imaging data (S102); and calculating according to the intrinsic imaging data to obtain an intrinsic time domain stability parameter of the coil (S103). All complex physiological noises possibly existing in functional magnetic resonance acquisition can be eliminated, and only time domain noises caused by relative motion between the radio frequency receiving coil and the tested phantom are considered; and the acquired intrinsic time domain stability parameter can be used for guiding design and use of a special radio frequency receiving coil in an FMRI application, and improving the image performance of FMRI.

Description

A method for measuring intrinsic time domain stability parameters of radiofrequency receiving coils in fMRI

Technical field

The invention belongs to the technical field of functional magnetic resonance imaging, and specifically relates to a method for measuring the intrinsic time domain stability parameters of radio frequency receiving coils in fMRI.

Background technique

In the 7T (tesla, Tesla) ultra-high field magnetic resonance imaging system, due to the increase in magnetic field strength, the image signal-to-noise ratio and the contrast when detecting neuronal activity in functional magnetic resonance imaging (fMRI, functional Magnetic Resonance Imaging) It has also improved accordingly, so ultra-high field magnetic resonance is widely used in sub-millimeter functional imaging. However, in ultra-high field magnetic resonance imaging, as the magnetic field intensity increases, the time-domain noise utilized by the subject's motion also increases, thus greatly weakening the imaging potential that can be achieved under ultra-high fields. To date, functional magnetic resonance imaging has mainly focused on improving data acquisition methods, such as image post-processing and motion correction algorithms, in mitigating temporal noise, but few can fundamentally solve the problem of magnetic field strength-related temporal noise.

Among them, the time-domain noise related to the magnetic field strength can be attributed to the radio frequency operating frequency that increases with the field strength, which causes a more complex interaction between the electromagnetic field and the subject. Specifically, the electrodynamic coupling between the imaging subject and the radio frequency coil acts as a dielectric load. When the spatial position of the radio frequency receiving coil changes relative to the imaging subject, the electrodynamic coupling will be disturbed; when the coil and the imaged subject The electrodynamic coupling will reach a steady state only when the distance remains constant.

In the existing technology, MRI (Magnetic Resonance Imaging, Magnetic Resonance Imaging) acquisition sequences and image post-processing algorithms often assume a constant coupling level between the radio frequency receiving coil and the subject, but this is obviously not applicable in fMRI. The reason is that changes within the human brain inevitably occur during functional magnetic resonance scanning. Even if the subject's head is stationary, there will be non-rigid movement of brain tissue, as well as the flow of blood and cerebrospinal fluid, which will interfere with the imaging. The interaction between the test and the RF receiving coil. Although some scholars have studied the involvement of radio frequency receiving coils in affecting the time domain signal-to-noise ratio (tSNR, time SIGNAL NOISE RATIO) of functional magnetic resonance imaging, these studies have been unable to separate the radio frequency receiving coils from other noises, such as physiological noise, and thus cannot Knowing what kind of time domain noise the RF receiving coil itself brings makes it impossible to know whether the RF receiving coil is suitable for functional magnetic resonance imaging.

Therefore, there is an urgent need to propose a method that can effectively measure the time domain noise caused by the radio frequency receiving coil itself in functional magnetic resonance imaging.

Contents of the invention

The purpose of the present invention is to provide a method for measuring the intrinsic time domain stability parameters of a radio frequency receiving coil in fMRI, which is used to solve the problem that the existing technology method cannot separate the radio frequency receiving coil from other noise, and thus cannot know the radio frequency receiving coil itself. What kind of technical issues will be brought about in the time domain noise.

In order to achieve the above objects, the present invention adopts the following technical solutions:

In a first aspect, the present invention provides a method for measuring intrinsic time domain stability parameters of a radio frequency receiving coil in fMRI, including:

The distance between the coil and the phantom is changed by inserting dielectric pieces of different thicknesses between the RF receiving coil and the simulated phantom to simulate the relative motion between the coil and the phantom. The dielectric pieces need to meet the conductivity requirements. Less than 1×10 ^-15 S/m, relative dielectric constant between 1-3;

Collect multiple echo EPI images of the subject simulation phantom when inserting dielectric parts of different thicknesses, and process and reconstruct the original K-space data of the multiple echo EPI images to obtain intrinsic imaging data;

The intrinsic time domain stability parameters of the coil are calculated according to the intrinsic imaging data. The intrinsic time domain stability parameters at least include the intrinsic time domain signal-to-noise ratio, the intrinsic time domain sensitivity stability and the intrinsic time domain stability. Thermal noise stability.

In a possible design, the radio frequency receiving coil includes at least a single-channel receiving coil and/or a multi-channel receiving array coil.

In one possible design, the subject simulation phantom includes a water phantom, and a filling liquid that simulates the electrical properties of the human body is provided inside the water phantom. The electrical properties at least include dielectric constant and conductivity.

In one possible design, the media member includes a plastic pad filled with polytetrafluoroethylene material.

In one possible design, multiple echo EPI images of the subject's simulation phantom are collected when inserting dielectric members of different thicknesses, including:

When inserting a dielectric member of each thickness, use a short TE sequence to perform proton density-weighted imaging on the subject simulation phantom, set N time domain sampling points/times, and collect multiple sets of echoes at different voxel resolutions. Wave EPI image.

In a possible design, when a single-channel receiving coil is used, the original K-space data of multiple echo EPI images are processed and reconstructed to obtain intrinsic imaging data, including:

Fourier transform is used to process and reconstruct the original K-space echo data to obtain intrinsic imaging data, where the matrix size of the intrinsic imaging data is consistent with the k-space matrix size.

In a possible design, when a multi-channel receiving array coil is used, the original K-space data of multiple echo EPI images are processed and reconstructed to obtain intrinsic imaging data, including:

The sum of squares method is used to perform a weighted combination reconstruction of the three-dimensional multi-channel echo data in the original K space, and the intrinsic imaging data after multi-channel information compression is obtained.

In one possible design, the coil intrinsic time domain stability parameters are calculated based on the intrinsic imaging data, including:

According to the time domain data of the intrinsic imaging data collected using different voxel resolutions, the intrinsic time domain signal-to-noise ratio tSNR ^* corresponding to different voxel resolutions is calculated, including:

Calculate the time domain mean and time domain standard deviation of each pixel, and use the time domain mean as the intrinsic time domain sensitivity mean of the coil

And the time domain standard deviation is regarded as the coil's intrinsic time domain noise standard deviation σ _t ^* ′;

According to the intrinsic time domain sensitivity mean

and the intrinsic time domain noise standard deviation σ _t ^* ′, the intrinsic time domain signal-to-noise ratio tSNR ^* is calculated, where,

In a possible design, before calculating the intrinsic time domain stability parameters of the coil based on the intrinsic imaging data, the method further includes:

The intrinsic imaging data collected when the radio frequency power is turned on is used as the coil intrinsic sensitivity data S ^* ;

The intrinsic imaging data collected when the RF power is turned off is used as thermal noise data, and the thermal noise standard deviation is calculated.

According to the coil intrinsic sensitivity data S ^* and the thermal noise standard deviation

Calculate the intrinsic signal-to-noise ratio SNR ^* ,

In a possible design, the coil intrinsic time domain stability parameters are calculated based on the intrinsic imaging data, including:

The time-domain standard deviation of the coil intrinsic sensitivity data S ^* is normalized and calculated to obtain the intrinsic time-domain sensitivity stability λ ^* ,

Among them, σ _s ^* represents the time domain standard deviation of the coil intrinsic sensitivity;

The time domain standard deviation of the thermal noise data is normalized and calculated to obtain the thermal noise stability α ^* in this time domain,

in,

Represents the time domain standard deviation of the subject's simulated phantom noise.

In a second aspect, the present invention provides a device for measuring intrinsic time domain stability parameters of radio frequency receiving coils in fMRI, including:

The relative motion simulation module is used to change the coil-phantom distance by inserting dielectric pieces of different thicknesses between the radio frequency receiving coil and the subject simulation phantom to simulate the relative motion between the coil and the phantom, where The above-mentioned dielectric parts need to have a conductivity less than 1×10 ^-15 S/m and a relative dielectric constant between 1 and 3;

An imaging data collection module is used to collect multiple echo EPI images of the subject simulation phantom when inserting dielectric parts of different thicknesses, and process and reconstruct the original K-space data of the multiple echo EPI images, Obtain intrinsic imaging data;

A time domain parameter calculation module, used to calculate the intrinsic time domain stability parameters of the coil based on the intrinsic imaging data. The intrinsic time domain stability parameters at least include the intrinsic time domain signal-to-noise ratio, the intrinsic time domain signal-to-noise ratio, and the intrinsic time domain stability parameters. Sensitivity stability and intrinsic time-domain thermal noise stability.

In a third aspect, the present invention provides a computer device, including a memory, a processor and a transceiver that are communicatively connected in sequence, wherein the memory is used to store computer programs, the transceiver is used to send and receive messages, and the processor is used to read Take the computer program and execute the method for measuring the intrinsic time domain stability parameters of the radio frequency receiving coil in fMRI as described in any possible design of the first aspect.

In a fourth aspect, the present invention provides a computer-readable storage medium. Instructions are stored on the computer-readable storage medium. When the instructions are run on a computer, the instructions are executed as described in any possible design of the first aspect. The method for measuring the intrinsic time domain stability parameters of radiofrequency receiving coils in fMRI is described.

In a fifth aspect, the present invention provides a computer program product containing instructions. When the instructions are run on a computer, the computer is caused to execute the radio frequency receiving coil in fMRI as described in any possible design of the first aspect. Method for measuring intrinsic time domain stability parameters.

Beneficial effects:

The present invention changes the distance between the coil and the phantom by inserting dielectric pieces of different thicknesses between the radio frequency receiving coil and the subject's simulation phantom to simulate the relative motion between the coil and the phantom, thus eliminating all possible functional problems. The complex physiological noise in magnetic resonance acquisition only considers the time domain noise caused by the relative motion between the radio frequency receiving coil and the subject phantom; by collecting multiple images of the subject simulation phantom when inserting dielectric parts of different thicknesses Echo EPI images, and process and reconstruct multiple echo images to obtain intrinsic imaging data; calculate the intrinsic time domain stability parameters of the coil based on the intrinsic imaging data, and the intrinsic time domain stability parameters at least include the intrinsic Time domain signal-to-noise ratio, intrinsic time domain sensitivity stability and intrinsic time domain thermal noise stability. This intrinsic time domain stability parameter can be used to guide the design and use of dedicated RF receiving coils in functional magnetic resonance imaging applications. Improving image performance in functional magnetic resonance imaging.

Description of the drawings

Figure 1 is a flow chart of the method for measuring the intrinsic time domain stability parameters of the radio frequency receiving coil in fMRI in this embodiment.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of this specification clearer, the technical solutions in the embodiments of this specification will be clearly and completely described below in conjunction with the drawings in the embodiments of this specification. Obviously, the described embodiments These are part of the embodiments in this specification, not all of them. Based on the embodiments in this specification, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

Example

Since the electromagnetic field of the radio frequency receiving coil determines the intrinsic sensitivity and intrinsic thermal noise level of the magnetic resonance signal, based on this, the concept of intrinsic signal-to-noise ratio SNR ^* has been proposed. Through the intrinsic signal-to-noise ratio SNR ^* , it can be based on numerical electromagnetic simulation calculation to determine the upper limit of the image signal-to-noise ratio during actual magnetic resonance scanning; however, the intrinsic signal-to-noise ratio cannot evaluate the dynamic noise caused by the time domain signal. Therefore, the intrinsic time domain performance of the RF receiving coil should be quantified and can Used to evaluate the contribution of the RF receiving coil to time domain noise.

In addition, since the intrinsic sensitivity of the magnetic resonance signal and the intrinsic thermal noise level determined by the electrodynamics of the radio frequency receiving coil fluctuate during MRI scanning, this embodiment defines it as intrinsic time domain noise. Due to the shorter radio frequency wavelength of UHF (Ultra High Frequency), the resulting intrinsic time-domain noise may be the main component of the time-domain noise related to the magnetic field strength, thereby deteriorating the imaging performance at the sub-millimeter spatial scale, so , the determination of intrinsic time domain noise is of great significance for improving imaging performance.

In addition, modern MRI systems use a phased array design of radio frequency receiving coils to achieve a relatively high image signal-to-noise ratio over a larger field of view, and at the same time, parallel imaging technology can be implemented to improve image coding efficiency. However, there are complex electrodynamic couplings between different units of the coil and the test load, which will inevitably affect the sensitivity, thermal noise and noise amplification factor (g factor) of parallel imaging. The perturbation of this electrodynamic coupling will lead to changes in the mutual coupling between phased array units, thereby making the intrinsic time domain noise more complex. At present, there is no way to separate the radio frequency receiving coil from other noise, such as physiological noise, so that it is impossible to know what kind of time domain noise the radio frequency receiving coil itself brings, and then it is impossible to know whether the radio frequency receiving coil is suitable for functional magnetic resonance imaging. Based on this, this embodiment proposes a method for measuring the intrinsic time domain stability parameters of the radio frequency receiving coil in fMRI, and measures the intrinsic time domain stability parameters of the radio frequency receiving coil through this method, which is used to guide functional magnetic resonance imaging. The design and use of dedicated radio frequency receiving coils in applications improve the image performance of functional magnetic resonance imaging. The method is illustrated below through examples, specifically as follows:

As shown in Figure 1, in the first aspect, this embodiment provides a method for measuring the intrinsic time domain stability parameters of a radio frequency receiving coil in fMRI, including but not limited to steps S101 to S103:

Step S101. Change the coil-phantom distance by inserting dielectric pieces of different thicknesses between the radio frequency receiving coil and the subject simulation phantom to simulate the relative motion between the coil and the phantom, where the dielectric piece needs to The electrical conductivity is less than 1×10 ^-15 S/m and the dielectric constant is between 1 and 3, that is, the impact of dielectric properties on the electromagnetic field is very small;

In step S101, the radio frequency receiving coil at least includes a single-channel receiving coil and/or a multi-channel receiving array coil. Preferably, in this embodiment, three single-channel receiving coils with diameters of 2cm, 3.5cm and 5cm are selected. And a 16-channel receiving array coil with a coverage area of 5cm diameter circle. Of course, it can be understood that this embodiment is not limited to coils with the above-mentioned diameter or the above-mentioned number of channels. Any coil structure that can achieve the purpose of the invention of this embodiment belongs to Within the protection scope of the present invention, there is no limitation here.

In step S101, the subject simulation phantom includes a water phantom, and a filling liquid that simulates the electrical characteristics of the human body is provided inside the water phantom. The electrical characteristics at least include dielectric constant and conductivity. Preferably, The water phantom adopts a uniform cylindrical water phantom with a bottom diameter of 11cm and a length of 20cm, and the filling liquid in the water phantom is deionized water containing 37.5% NiSO4·5H2O and 0.5% NaCl; of course, it can It should be understood that the subject simulation phantom in this embodiment is not limited to the use of water phantoms. Any phantom that can simulate the electrical characteristics of the subject's human body is suitable for the method of this embodiment. The conductivity of the simulation phantom is The dielectric constant is the same as that of the human body, and its parameters such as volume or shape can vary according to the simulation of different human bodies.

In step S101, the medium piece includes a plastic pad filled with polytetrafluoroethylene material. Preferably, in this embodiment, plastic pads with thicknesses of 3 mm, 6 mm and 8 mm are selected, and the simulated phantom is tested each time. Before scanning, insert a plastic pad of one thickness, and insert plastic pads of different thicknesses to change the distance between the coil and the subject's simulation phantom, thereby simulating the relative motion of the coil and the subject's simulation phantom; in addition, in order to To ensure that the impact of the dielectric component on the electromagnetic field characteristics of the radio frequency receiving coil is minimized, this embodiment selects a dielectric component with a dielectric property lower than the threshold. Preferably, the dielectric component is made of polytetrafluoroethylene material, that is, Teflon. The dielectric constant ε _r =2.1. Of course, it can be understood that other low dielectric constant materials can also be used in this embodiment, which is not limited here.

Step S102. Collect multiple echo EPI images of the subject simulation phantom when inserting dielectric parts of different thicknesses, and process and reconstruct the original K-space data of the multiple echo EPI images to obtain intrinsic imaging. data;

Wherein, it should be noted that preferably, the echo image is a single echo EPI (Echo Planar Imaging) image.

In a specific implementation of step S102, multiple echo EPI images of the subject simulation phantom when inserting dielectric members of different thicknesses are collected, including:

When inserting a dielectric member of each thickness, use a short TE sequence to perform proton density-weighted imaging on the subject simulation phantom, set N time domain sampling points/times, and collect multiple sets of echoes at different voxel resolutions. wave image.

Among them, preferably, this embodiment sets 30 time domain sampling points/time, and collects voxel sizes of 0.85×0.85×1mm3, 1.15×1.15×1mm3, 1.45×1.45×1mm3, 1.75×1.75×1mm3, 2× 2×1mm3 echo images, so that different intrinsic signal-to-noise ratios can be obtained. It should be noted that when collecting each set of data, only the scanning parameter of voxel size is changed, while other parameters, such as imaging range, contrast, etc., are not affected as much as possible. Therefore, only the voxel size of the collected image can be changed. to obtain different intrinsic signal-to-noise ratios. Then, this embodiment can collect a set of 30 temporally discrete data points at each voxel size, and the intrinsic signal-to-noise ratio of the 30 data points is consistent, so that the signal-to-noise ratio data can be calibrated.

In a specific implementation of step S102, when a single-channel receiving coil is used, the original K-space data of multiple echo EPI images are processed and reconstructed to obtain intrinsic imaging data, including:

Specifically, the original K-space echo data Nx*Ny is reconstructed through Fourier transform to obtain the image data Nx'*Ny', where Nx and Ny are the number of echo samples and the number of phase encoding respectively, and Nx'*Ny' are respectively Corresponds to the number of columns and rows of the image, and the matrix size of the image is consistent with the k-space matrix size.

In a specific implementation of step S102, when a multi-channel receiving array coil is used, the original K-space data of multiple echo EPI images are processed and reconstructed to obtain intrinsic imaging data, including:

The sum of squares method is used to perform weighted combination reconstruction of the three-dimensional multi-channel echo data in K-space, and the intrinsic imaging data after multi-channel information compression is obtained.

Specifically, for the three-dimensional multi-channel echo data Nx*Ny*Nch in K space, Nch is the number of receiving coil channels, it needs to be compressed, that is, compressed to two-dimensional data, that is, weighted combination reconstruction is performed through the sum of squares method. , to obtain the intrinsic imaging data.

Step S103. Calculate the intrinsic time domain stability parameters of the coil according to the intrinsic imaging data. The intrinsic time domain stability parameters at least include the intrinsic time domain signal-to-noise ratio, the intrinsic time domain sensitivity stability and the intrinsic time domain sensitivity stability. Thermal noise stability in the time domain.

Among them, it should be noted that the intrinsic time domain signal-to-noise ratio refers to only considering the relative motion of the radio frequency receiving coil and the subject sample, and is determined by factors such as the sensitivity of the radio frequency receiving coil, thermal noise, and the time domain fluctuations of the two. The time domain signal-to-noise ratio performance parameter is used to evaluate whether a specific radio frequency receiving coil is suitable for time domain acquisition applications such as functional magnetic resonance imaging, that is, the time domain noise caused by the relative motion of the radio frequency receiving coil and the subject sample is also considered. , as well as the sensitivity and thermal noise of the RF receiving coil.

In a specific implementation of step S103, coil intrinsic time domain stability parameters are calculated according to the intrinsic imaging data, including:

According to the intrinsic time domain sensitivity mean

In a specific implementation of step S103, before calculating the intrinsic time domain stability parameters of the coil according to the intrinsic imaging data, the method further includes:

Calculate the intrinsic signal-to-noise ratio SNR ^* ,

in,

Among them, it should be noted that the thermal noise stability α ^* in this time domain can also be obtained by fitting the relationship between the intrinsic signal-to-noise ratio SNR ^* and tSNR ^* . In order to verify whether the model parameter α ^* can characterize the thermal noise For time domain stability, calculate the normalized time domain variance Var of thermal noise for the noise-only data of each receiving coil, and then analyze the relationship between it and α ^* through linear regression analysis. If the two are the same or similar, This shows that the model parameter α ^* can characterize the time domain stability of thermal noise.

Based on the above disclosure, this embodiment changes the coil-phantom distance by inserting dielectric pieces of different thicknesses between the radio frequency receiving coil and the subject simulation phantom to simulate the relative motion between the coil and the phantom, thereby All complex physiological noise that may exist in functional magnetic resonance acquisition can be eliminated, and only the time domain noise caused by the relative motion between the radio frequency receiving coil and the subject phantom is considered; through the acquisition, when inserting dielectric pieces of different thicknesses, Try to simulate multiple echo EPI images of the phantom, process and reconstruct the multiple echo images to obtain the intrinsic imaging data; calculate the intrinsic time domain stability parameters of the coil based on the intrinsic imaging data, and the intrinsic time domain stability parameters of the coil. Stability parameters include at least intrinsic time domain signal-to-noise ratio, intrinsic time domain sensitivity stability, and intrinsic time domain thermal noise stability. The intrinsic time domain stability parameters can be used to guide dedicated radio frequency in functional magnetic resonance imaging applications. The design and use of receiving coils improves the image performance of functional magnetic resonance imaging.

The relative motion simulation module is used to change the coil-phantom distance by inserting dielectric pieces of different thicknesses between the radio frequency receiving coil and the subject simulation phantom to simulate the relative motion between the coil and the phantom, where The above-mentioned dielectric parts need to have a conductivity less than 1×10 ^-15 S/m and a dielectric constant between 1-3;

For the working process, working details and technical effects of the aforementioned device provided in the second aspect of this embodiment, please refer to the above first aspect or the method described in any possible design of the first aspect, and will not be described again here.

For specific examples, the memory may include, but is not limited to, random access memory (Random-Access Memory, RAM), read-only memory (Read-Only Memory, ROM), flash memory (Flash Memory), first-in first-out memory (First Input First Output, FIFO) and/or First Input Last Output, FILO, etc.; the processor may not be limited to microprocessors of the STM32F105 series; the transceiver may be, but is not limited to, WiFi (Wireless Fidelity) wireless transceiver, Bluetooth wireless transceiver, GPRS (General Packet Radio Service, General Packet Radio Service Technology) wireless transceiver and/or ZigBee (Zigbee protocol, a low-power LAN protocol based on the IEEE802.15.4 standard ) wireless transceiver, etc. In addition, the computer device may also include, but is not limited to, a power module, a display screen and other necessary components.

The working process, working details and technical effects of the aforementioned computer equipment provided in the third aspect of this embodiment can be referred to the above first aspect or the method described in any possible design of the first aspect, and will not be described again here.

Wherein, the computer-readable storage medium refers to a carrier for storing data, which may, but is not limited to, include floppy disks, optical disks, hard disks, flash memory, USB flash drives and/or memory sticks, etc. The computer may be a general-purpose computer, a special-purpose computer, etc. Computer, computer network, or other programmable device.

For the working process, working details and technical effects of the computer equipment provided in the fourth aspect of this embodiment, please refer to the above first aspect or the method described in any possible design of the first aspect, and will not be described again here.

For the working process, working details and technical effects of the computer-readable storage medium provided in the fifth aspect of this embodiment, please refer to the above first aspect or the method described in any possible design of the first aspect, and will not be described again here. .

Finally, it should be noted that the above descriptions are only preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

A method for measuring intrinsic time domain stability parameters of radiofrequency receiving coils in fMRI, which is characterized by including:

The distance between the coil and the phantom is changed by inserting dielectric pieces of different thicknesses between the RF receiving coil and the simulated phantom to simulate the relative motion between the coil and the phantom. The dielectric pieces need to meet the conductivity requirements. Less than 1×10 -15 S/m, relative dielectric constant between 1-3;

Collect multiple echo EPI images of the subject simulation phantom when inserting dielectric parts of different thicknesses, and process and reconstruct the original K-space data of the multiple echo EPI images to obtain intrinsic imaging data;

The intrinsic time domain stability parameters of the coil are calculated according to the intrinsic imaging data. The intrinsic time domain stability parameters at least include the intrinsic time domain signal-to-noise ratio, the intrinsic time domain sensitivity stability and the intrinsic time domain stability. Thermal noise stability.
The method for measuring intrinsic time domain stability parameters of a radio frequency receiving coil in fMRI according to claim 1, wherein the radio frequency receiving coil at least includes a single-channel receiving coil and/or a multi-channel receiving array coil.
The method for measuring intrinsic time domain stability parameters of radio frequency receiving coils in fMRI according to claim 1, characterized in that the subject simulation phantom includes a water phantom, and the water phantom is equipped with a simulated human body electrical The electrical properties of the filling liquid include at least dielectric constant and conductivity.
The method for measuring intrinsic time domain stability parameters of radio frequency receiving coils in fMRI according to claim 1, wherein the dielectric member includes a plastic pad filled with polytetrafluoroethylene material.
The method for measuring intrinsic time domain stability parameters of radio frequency receiving coils in fMRI according to claim 1, characterized in that multiple echo EPI images of the subject simulation phantom are collected when inserting dielectric parts of different thicknesses. ,include:

When inserting a dielectric member of each thickness, use a short TE sequence to perform proton density-weighted imaging on the subject simulation phantom, set N time domain sampling points/times, and collect multiple sets of echoes at different voxel resolutions. Wave EPI image.
The method for measuring intrinsic time domain stability parameters of radio frequency receiving coils in fMRI according to claim 2, characterized in that when a single-channel receiving coil is used, the original K-space data of a plurality of the echo EPI images are measured. Process the reconstruction to obtain intrinsic imaging data, including:

Fourier transform is used to process and reconstruct the original K-space echo data to obtain intrinsic imaging data, where the matrix size of the intrinsic imaging data is consistent with the K-space matrix size.
The method for measuring intrinsic time domain stability parameters of radio frequency receiving coils in fMRI according to claim 2, characterized in that when a multi-channel receiving array coil is used, the original K-space data of a plurality of the echo EPI images Perform processing and reconstruction to obtain intrinsic imaging data, including:

The sum of squares method is used to perform a weighted combination reconstruction of the three-dimensional multi-channel echo data in the original K space, and the intrinsic imaging data after multi-channel information compression is obtained.
The method for measuring intrinsic time domain stability parameters of radio frequency receiving coils in fMRI according to claim 5, characterized in that the coil intrinsic time domain stability parameters are calculated according to the intrinsic imaging data, including:

According to the time domain data of the intrinsic imaging data collected using different voxel resolutions, the intrinsic time domain signal-to-noise ratio tSNR * corresponding to different voxel resolutions is calculated, including:

Calculate the time domain mean and time domain standard deviation of each pixel, and use the time domain mean as the intrinsic time domain sensitivity mean of the coil
And the time domain standard deviation is regarded as the coil's intrinsic time domain noise standard deviation σ t * ′;

According to the intrinsic time domain sensitivity mean
and the intrinsic time domain noise standard deviation σ t * ′, the intrinsic time domain signal-to-noise ratio tSNR * is calculated, where,
The method for measuring intrinsic time domain stability parameters of radio frequency receiving coils in fMRI according to claim 8, characterized in that, before calculating the intrinsic time domain stability parameters of the coil according to the intrinsic imaging data, the Methods also include:

The intrinsic imaging data collected when the radio frequency power is turned on is used as the coil intrinsic sensitivity data S * ;

The intrinsic imaging data collected when the RF power is turned off is used as thermal noise data, and the thermal noise standard deviation is calculated.

According to the coil intrinsic sensitivity data S * and the thermal noise standard deviation
Calculate the intrinsic signal-to-noise ratio SNR * ,
The method for measuring intrinsic time domain stability parameters of radio frequency receiving coils in fMRI according to claim 9, characterized in that the coil intrinsic time domain stability parameters are calculated according to the intrinsic imaging data, including:

The time-domain standard deviation of the coil intrinsic sensitivity data S * is normalized and calculated to obtain the intrinsic time-domain sensitivity stability λ * ,
Among them, σ s * represents the time domain standard deviation of the coil intrinsic sensitivity;

The time domain standard deviation of the thermal noise data is normalized and calculated to obtain the thermal noise stability α * in this time domain,
in,
Represents the time domain standard deviation of the subject's simulated phantom noise.