High-linearity gradient coil design method

Abstract

The invention discloses a high-linearity gradient coil design method, and the method comprises the steps: proposing two new Fourier series expansion current density functions, and introducing a stream function; selecting discrete target points in the N target areas, deducing a magnetic field expression of the target field points according to the Biot-Savart law, and constructing a relation matrix between the magnetic field expression and the current density function; setting a value of a target field point, selecting a minimum curvature of a flow function as a penalty function of a constraint coil, setting a constraint factor of the penalty function, solving an undetermined coefficient in a current density expression through a regularization method, and obtaining a current density distribution condition of the cylindrical surface; the current density is discretized using a stream function to generate a winding diagram of the coil. The gradient coil is designed by improving the target field method, so that the linearity of the gradient field is greatly improved; the size of the cylindrical coil is preset before calculation, so that the limitation on the size is overcome; curvature constraint and regularization methods are introduced to solve the ill-conditioned problem of solutions, so that the gradient coil is convenient to process and manufacture.

Description

technical field [0001] The invention relates to a high linearity gradient coil design method, the linearity error of the designed radial gradient coil is less than 0.9%, and the linearity error of the axial gradient coil is less than 0.5%, which can be applied to nuclear magnetic resonance imaging systems and SERF atomic magnetometers Fields requiring high linearity gradient magnetic fields such as measurement systems. Background technique [0002] The gradient coil is one of the most important components of the magnetic resonance system, and the gradient coil can generate a magnetic field with a gradient change in the imaging area when a current is applied to the gradient coil. The function of the gradient coil is mainly to encode the space and distinguish the MRI signals of different positions. In addition, in the field of SERF-based atomic magnetometer measurement and imaging, in order to realize the SERF state of atomic spin, passive magnetic shielding, including magnet...

AI Technical Summary

Problems solved by technology

[0004] The technical problem of the present invention is to overcome the deficiencies of the prior art, provide a design method of a gradient coil with high linearity, solve the problem that the axial magnetic field and the gradient magnetic field of the single-end opening of the magnetic shielding barrel are relatively large, and design by improving the target field method The gradient coil greatly improves the linearity of the gradient field; and the size of the cylindrical coil is preset before calculation, which overcomes the limitation on the size; the curvature constraint and regularization method are introduced to solve the ill-conditioned problem of the solution, so that the gradient coil Easy to process and make

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