Gradient Coil Design In Parallel Imaging With Nonlinear Encoding

Magnetic resonance imaging (MRI) has been extensively used in various fields,and it requires for higher imaging speed and more openness degree. Nonlinearencoding parallel acquisition techniques and parallel algorithms of themulti-channel imaging technology become a new research hot point to improve thespeed of MRI. Unconventional Nuclear Magnetic Resonance (UNMR) instrumentprovides more open degree because its structure is different from that of theconventional magnet enclosing the sample. UNMR expands range of applications ofMRI systems. However, Imaging speed is a bottleneck for UNMR application. Weapplied nonlinear encoding parallel imaging techniques to UNMR. Moreover, thenon-linear gradient magnetic field gradient coil was designed using target fieldmethod.Firstly, the infinitely long non-linear gradient magnetic field coil was designedby the traditional target field method. The paper will analyze characteristics ofnonlinear parallel imaging gradient field and boundary conditions of unconventionalimaging system magnet, and then apply electromagnetic theory and methods ofmathematics and physics derivation to build mathematical model of the magneticfield and current. During the period of testing and verifying the result by simulatingthe mathematical model, the paper will focus on analyzing the selection of samplingpoints on the gradient magnetic field and current distribution.Secondly, planar gradient coil of finite length size of the non-linear gradientmagnetic field was designed by the novel target-field method. The novel target-fieldmethod utilizes the periodic function to constrain the coils current in a finite area.Current density of the series expands the expression of the deduced magnetic field.Compared to the traditional target field method, the novel target-field methoddesign the finite length size coils can be achieved easily. Furthermore, the noveltarget-field method develops the target field theory.