Design And Optimization Of A Planar Gradient Coil System

Magnetic resonance imaging is an essential medical imaging tool with three main features,including non-ionization,non-radioactive and non-intrusion.The existing magnetic resonance devices in hospitals and laborites were developed based on the spin of 1H in the water molecule.However,some human organs such as lung do not meet this harsh requirement.This project aimed to design a low field magnetic resonance imaging for imaging of lung and to use the corecomponent-gradient system as the entry point to introduce the principle of magnetic imaging.Additionally,this thesis presents a brief introduction to the gas polarization of 3 HE,which is a crucialcomponent in magnetic resonance imaging for diagnosing of lung cancer.In the aspect of the gradient system,this thesis aims to design a target field gradient coil and a high-performance gradient power amplifier.The proposed method is not only limited for low field magnetic resonance imaging but also can be applied to other kinds of magnetic resonance devices.This project contains the following tasks.1)Develop a gradient coil with target field for application in permanent magnetic resonance imaging system,which has a specific distance from target imaging area;2)Compute the current density of a target field(target harmonic coefficient using Biot-Savart law;3)Solve the current stream function using steady flow condition;4)Numerical validate the proposed coil using MATLAB;5)Develop a high-performance gradient power amplifier with some features,such as accurate,rising and declining for output and input current on microsecond level with fractional fluctuate,using dead time to ensure the signal switch speed and prevent short circuit situation efficiently.The proposed gradient power amplifier has been experimentally validated,and the results showed that the design produceshigh precision level of control and stable current output.