Optimal Design Of Main Magnet In Magnetic Resonance Imaging (mri)

Magnetic resonance imaging (MRI) is a new medical imaging technology. Based on nuclear magnetic resonance theory, such technology can image for human organs in a homogeneous magnetic field. The quality of the imaging depends highly on the magnetic field homogeneity of magnet system. The work in this paper is supported by an important project 863 "Study of 0.6T MgB2 Magnetic Resonance Imaging System". The work studies mainly on magnetic field homogeneity.Main work in this paper is described as follow:(1) Finite element analysis for the magnetic fieldCombined the basic theory of the electromagnetic fields with finite element analysis methods (FEM), we obtain the magnetic field distribution law by using "ANSYS" software for magnetic field analysis of main magnet in MRI. In order to improve the computation speed, three-dimensional analysis is replaced by two-dimensional analysis without the influence of precise.(2) Optimal design for shimming-boardAccording to the shimming-board role in magnet, basic structure of shimming-board is designed. Using ANSYS Parametric Design Language (APDL) for coding optimization algorithm program, we obtain the optimal solution with magnetic field homogeneity as the objective function. The general steps of shimming-board optimal design are generalized.(3) The comparative analysis between experiment and calculationBases on the present experimental conditions, both the experimental equipment and experimental method are properly chosen. Comparing analysis of the calculation results with the experimental results, we prove the validity of optimal design. The sources of the experimental errors are generalized, the influence of errors is analyzed, and the methods of reducing errors are proposed.