CN-121997604-A - Magnetic resonance radio frequency shimming optimization method and device based on spatial weight and adaptive weight

CN121997604ACN 121997604 ACN121997604 ACN 121997604ACN-121997604-A

Abstract

The application discloses a magnetic resonance radio frequency shimming optimization method and device based on spatial weight and adaptive weight. The magnetic resonance radio frequency shimming optimization method based on the spatial weight and the self-adaptive weight comprises the steps of obtaining excitation field distribution to be optimized, obtaining a target area excitation magnetic field matrix, a peripheral area excitation magnetic field matrix and an objective function according to the excitation field distribution to be optimized, dynamically updating the outer Zhou Quan weight through an iterative self-adaptive weight mechanism according to the target area excitation magnetic field matrix, the peripheral area excitation magnetic field matrix and the objective function, so that final channel complex weights are generated, and transmitting the final channel complex weights to a magnetic resonance emission system, so that the magnetic resonance emission system realizes radio frequency shimming according to the final channel complex weights. The final channel complex weight generated by the application can balance peripheral response while guaranteeing the performance of the target area, and realize the uniformity control of the field of each area B 1 ﹢ .

Inventors

WANG YINING
LI YE
LI NAN
LIANG DONG
SUN YUE

Assignees

中国医学科学院北京协和医院

Dates

Publication Date: 20260508
Application Date: 20260129

Claims (8)

1. The magnetic resonance radio frequency shimming optimization method based on the spatial weight and the adaptive weight is characterized by comprising the following steps of: Obtaining excitation field distribution to be optimized; acquiring a target area excitation magnetic field matrix, a peripheral area excitation magnetic field matrix and a target function according to the excitation field distribution to be optimized; dynamically updating the outer Zhou Quan weight according to the target area excitation magnetic field matrix, the peripheral area excitation magnetic field matrix and the objective function through an iterative self-adaptive weight mechanism, so as to generate a final channel complex weight; And transmitting the final channel complex weights to a magnetic resonance transmitting system, so that the magnetic resonance transmitting system realizes radio frequency shimming according to the final channel complex weights.
2. The method of magnetic resonance radio frequency shimming optimization based on spatial weighting and adaptive weighting as set forth in claim 1, wherein the acquiring the excitation field distribution to be optimized comprises: B 1 ﹢ field response data are obtained in an experimental acquisition mode or a simulation calculation mode; Acquiring response matrix of multi-channel B 1 ﹢ field response data according to B 1 ﹢ field response data Wherein N is the total number of pixels or voxels, The number of channels, C is the complex domain.
3. The method for optimizing magnetic resonance radio frequency shimming based on spatial weight and adaptive weight according to claim 2, wherein the acquiring the target mask, the peripheral mask, the target region excitation magnetic field matrix, the residual region excitation magnetic field matrix according to the excitation field distribution to be optimized comprises: dividing voxels into a core target region and a peripheral region according to the anatomical structure, defining a target mask Outer Zhou Yanmo Counting the number of pixels 、 ; From the response matrix Extracting target area excitation magnetic field matrix Excitation magnetic field matrix of residual region Setting ideal excitation magnetic field matrix of target area Ideal excitation magnetic field matrix in peripheral region ; Exciting a magnetic field matrix according to a target area Calculating uniformity weights of target areas ; Exciting a magnetic field matrix according to a target area Excitation magnetic field matrix of residual region Calculating remaining area control weights 。
4. A magnetic resonance radio frequency shimming method based on spatial and adaptive weighting as set forth in claim 3, characterized in that the objective function formula is as follows: wherein, the method comprises the steps of, Exciting a magnetic field matrix for a target region, Exciting a magnetic field matrix for the remaining region; an ideal excitation magnetic field matrix for the target area, An ideal excitation magnetic field matrix for the peripheral region; The uniformity weight of the target area; weights are controlled for the remaining regions.
5. The method of magnetic resonance radio frequency shimming optimization based on spatial weighting and adaptive weighting as set forth in claim 4, wherein dynamically updating the outer Zhou Quan weights by iterative adaptive weighting mechanism to generate final channel complex weights comprises: setting initialization iteration parameters, namely setting iteration times k=0 and setting initialization outside Zhou Quanchong = ; The following iterations are repeated until the iteration condition is satisfied: according to the response matrix Adaptively updating outer Zhou Quan weight, thereby obtaining the (k+1) th outer Zhou Quanchong ; According to the k+1st time outer Zhou Quanchong Adjusting an objective function and solving complex weights, wherein the iteration condition is as follows: And stopping optimizing the iteration when the energy ratio variation of the complex weights of two adjacent iterations is lower than a threshold value, and outputting the complex weight obtained last time as the complex weight of the final channel.
6. The method for optimizing magnetic resonance radio frequency shimming based on spatial weighting and adaptive weighting according to claim 5, wherein the response matrix is based on Adaptively updating outer Zhou Quan weight, thereby obtaining the (k+1) th outer Zhou Quanchong Comprising the following steps: Calculating the field strength norm of the current region by using the channel excitation vector of the kth iteration Substituting the matrix to calculate the field strength norm of the target area Field strength norms in peripheral regions ; Dynamically updating Zhou Quanchong according to iterative formula Weight update is carried out to obtain the (k+1) th time of external Zhou Quanchong 。
7. The method of magnetic resonance radio frequency shimming optimization based on spatial weighting and adaptive weighting as set forth in claim 6, wherein the k+1st time is according to the outer Zhou Quanchong Adjusting the objective function and solving for complex weights includes: With updated Adjusting an objective function ; Optimizing by adopting an amplitude-phase separation strategy, firstly calculating in the kth round of outer circulation Extracting its phase This iteration is fixed Optimizing only the amplitude coefficient The complex weight is in the form of ; Solving the optimized solution by nonlinear least square or conjugate gradient method And obtaining the complex weight after the k-th round of optimization.
8. A magnetic resonance radio frequency shimming optimization device based on spatial weight and adaptive weight, characterized in that the magnetic resonance radio frequency shimming optimization device based on spatial weight and adaptive weight comprises: the excitation field distribution acquisition module is used for acquiring excitation field distribution to be optimized; the data acquisition module for iterative optimization is used for acquiring a target area excitation magnetic field matrix, a peripheral area excitation magnetic field matrix and an objective function according to excitation field distribution to be optimized; The final channel complex weight generation module is used for dynamically updating the outer Zhou Quan weight through an iterative self-adaptive weight mechanism according to the target area excitation magnetic field matrix, the peripheral area excitation magnetic field matrix and the objective function, so as to generate the final channel complex weight; And the transmitting module is used for transmitting the final channel complex weight to the magnetic resonance transmitting system, so that the magnetic resonance transmitting system realizes radio frequency shimming according to the final channel complex weight.

Description

Magnetic resonance radio frequency shimming optimization method and device based on spatial weight and adaptive weight Technical Field The application relates to the technical field of radio frequency shimming optimization, in particular to a magnetic resonance radio frequency shimming optimization method and device based on spatial weight and adaptive weight. Background Under the condition of high-field and ultra-high-field Magnetic Resonance Imaging (MRI), the radio frequency wavelength is obviously shortened along with the increase of the magnetic field intensity, and meanwhile, the medium resonance effect is enhanced, so that the in-vivo electromagnetic field distribution is more complex. For deep target imaging areas such as heart and liver, the excitation magnetic field B 1﹢ field often presents obvious non-uniformity, so that the fluctuation of image signal intensity and the local contrast reduction are caused, and the accuracy of quantitative measurement is affected. At the same time, peripheral tissues (e.g., subcutaneous fat, chest wall, etc.) are prone to forming local high electric field regions, thereby increasing the risk of local specific absorption rate SAR hot spots, which pose a potential threat to imaging safety. Although the existing multichannel parallel transmitting radio frequency shimming technology can improve the uniformity of the B 1﹢ field in the target area to a certain extent, the optimization strategy of the technology mostly adopts a unified weighting mode or a single target area weighting mode, and lacks flexible allocation and dynamic adjustment of importance of different anatomical areas. Although better uniformity can be obtained in the ROI, the situation that the field intensity is too high or too low occurs in the peripheral region, so that the local energy of the peripheral region is possibly concentrated excessively, potential safety hazards are brought, the overall uniformity of the image is possibly reduced, and popularization and application of the ultra-high-field MRI in clinic and scientific research are limited. (1) The magnetic resonance radio frequency shimming system with the prior art patent number of CN104515963A adopts a plurality of independent excitation sources and an optional multi-channel/multi-source framework, and improves the shimming control degree of freedom (more biased hardware/system layer) to solve the problem. But focuses on the system topology and channel number expansion, is not a voxel-level space weighting or iterative re-weighting optimization framework, and has higher cost due to hardware shimming. (2) The prior art patent CN111712719a, "shimming active B 1﹢ of the transmit coil," proposes introducing an active B 1﹢ shim coil outside the main transmit coil, to which rf power is supplied during transmission to improve the imaging region B 1﹢ uniformity. The active shimming design of the hardware level is more preferred. This solution requires an additional active B 1﹢ shim coil outside the main transmit coil and separate power and control during imaging. The structural complexity, cost and maintenance difficulty of the MRI system are increased, and the requirement on the improvement of the existing equipment is high. (3) The 'magnetic resonance radio frequency mode determination method, equipment and readable storage medium' of the prior art patent number CN113219389A mainly based on single-channel sensitivity pre-acquisition constructs a plurality of emission modes and sequentially/alternately excites to relieve high-field B 1﹢ unevenness and reduce SAR, and belongs to an emission mode level RF shimming strategy. This patent constructs multiple emission modes with single channel sensitivity and relies on alternate excitation to improve uniformity. However, the optimization target does not perform differentiation processing between the ROI and the non-ROI, and uniformity of the deep target and security of the peripheral region cannot be guaranteed. It is therefore desirable to have a solution that overcomes or at least alleviates at least one of the above-mentioned drawbacks of the prior art. Disclosure of Invention It is an object of the present application to overcome or at least alleviate at least one of the above-mentioned drawbacks of the prior art by providing a magnetic resonance radio frequency shimming optimization method based on spatial weights and adaptive weights. In order to achieve the above object, the present application provides a magnetic resonance radio frequency shimming optimization method based on spatial weight and adaptive weight, which comprises: Obtaining excitation field distribution to be optimized; acquiring a target area excitation magnetic field matrix, a peripheral area excitation magnetic field matrix and a target function according to the excitation field distribution to be optimized; dynamically updating the outer Zhou Quan weight according to the target area excitation magnetic field matrix, the peri