	US 12,092,714 B2
	Shimming method and device, electronic device, and storage medium
Hairong Zheng, Shenzhen (CN); Qiaoyan Chen, Shenzhen (CN); Ye Li, Shenzhen (CN); Chao Luo, Shenzhen (CN); and Xin Liu, Shenzhen (CN)
Assigned to SHENZHEN INSTITUTES OF ADVANCED TECHNOLOGY CHINESE ACADEMY OF SCIENCES, Shenzhen (CN)
Filed by SHENZHEN INSTITUTES OF ADVANCED TECHNOLOGY CHINESE ACADEMY OF SCIENCES, Shenzhen (CN)
Filed on Nov. 22, 2022, as Appl. No. 17/992,868.
Application 17/992,868 is a continuation of application No. PCT/CN2021/138523, filed on Dec. 15, 2021.
Claims priority of application No. 202111357763.8 (CN), filed on Nov. 16, 2021.
Prior Publication US 2023/0152400 A1, May 18, 2023
Int. Cl. G01R 33/3875 (2006.01); A61B 5/055 (2006.01)

CPC G01R 33/3875 (2013.01) [A61B 5/055 (2013.01)]

12 Claims

1. A shimming method, comprising:

obtaining object static magnetic field distribution information corresponding to a target object, wherein the object static magnetic field distribution information comprises static magnetic field distribution information of the target object under an action of a main magnet of a magnetic resonance system;

determining a target static magnetic field based on the object static magnetic field distribution information and a preset shim coil magnetic field distribution model; and

adjusting at least one shim coil parameter in the preset shim coil magnetic field distribution model until a magnetic field uniformity of the target static magnetic field satisfies a preset condition, and accordingly obtaining at least one target shim coil parameter;

wherein obtaining the object static magnetic field distribution information corresponding to the target object comprises:

obtaining object static magnetic field distribution information corresponding to each of a number of n target objects, n being a positive integer greater than 1;

and wherein accordingly, determining the target static magnetic field based on the object static magnetic field distribution information and the preset shim coil magnetic field distribution model comprises:

determining the target static magnetic field based on the respective object static magnetic field distribution information corresponding to each of the n target objects and the preset shim coil magnetic field distribution model;

wherein the adjusting the at least one shim coil parameter in the preset shim coil magnetic field distribution model until the magnetic field uniformity of the target static magnetic field satisfies the preset condition, and accordingly obtaining the at least one target shim coil parameter comprises:

for each of a plurality of shim coil magnetic field distribution models with different numbers of channels, adjusting at least one sub-shim coil parameter in the preset shim coil magnetic field distribution model according to a particle swarm algorithm and a preset objective function, until the number of iterations of the particle swarm algorithm reaches the preset number of times to obtain at least one sub-target shim coil parameter corresponding to each of the plurality of shim coil magnetic field distribution models;

determining the standard deviation of the magnetic field distribution of the target static magnetic field corresponding to each of the plurality of shim coil magnetic field distribution models based on the respective at least one sub-target shim coil parameter corresponding to each of the plurality of shim coil magnetic field distribution models and the objective function; and

taking the preset shim coil magnetic field distribution model with a minimum standard deviation of the magnetic field distribution of the target static magnetic field as a target shim coil magnetic field distribution model, and using the number of channels and the at least one sub-target shim coil parameter of the target shim coil magnetic field distribution model as the at least one target shim coil parameter;

wherein the for each of a plurality of shim coil magnetic field distribution models with different numbers of channels, adjusting at least one sub-shim coil parameter in the preset shim coil magnetic field distribution model according to a particle swarm algorithm and a preset objective function, until the number of iterations of the particle swarm algorithm reaches the preset number of times to obtain at least one sub-target shim coil parameter corresponding to each of the plurality of shim coil magnetic field distribution models comprises:

B0, for a shim coil magnetic field distribution model with a fixed number of channels, using a size, a spatial position, a current magnitude, and the number of turns of shim coils in the model as adjustable shim coil parameters in the shim coil magnetic field distribution model, designing a corresponding particle swarm;

B1: initializing the particle swarm, and assigning a random initial position and velocity to each group of parameters in the particle swarm;

B2: updating the instant particle swarm based on a velocity update formula and a position update formula; where the velocity update formula is as follows: V_i^k=w·V_i^k−1+c₁r₁(pbest_i−X_i^k−1)+c₂r₂(gbest_i−X_i^k−1); the position update formula is: X_i^k=X_i^k−1+V_i^k−1; wherein V_i^krepresents a speed of the k-th iteration parameter i, X_i^krepresents a position of the k-th iteration parameter i, pbest_irepresents a historical optimal position of the parameter i, gbest_irepresents a global optimal position of the parameter i, c1, c2 represents acceleration constants, r1, r2 represent two random parameters ranging from 0 to 1, w represents an inertia weight;

B3: according to the preset objective function, calculating a standard deviation of a target static magnetic field obtained after each set of parameters is substituted into the preset objective function, and determining whether to update the historical optimal position or the global optimal position depending on the standard deviation;

B4: determining whether the current number of iterations reaches the preset number; if yes, using a set of parameters corresponding to the current global optimal position as sub-target shim coil parameters corresponding to the current shim coil magnetic field distribution model; if no, returning to B2.