The Development Of New Digital Magnetic Resonance Spectrometer Receiver Based On PXIe Architecture

Magnetic Resonance Imaging system is an imaging examination equipment for medical diagnostics.Since it was put into clinical use,its development prospects have become broader because of its lack of electric radiation and clear display of soft tissue structure.Spectrometer is the center of control and data processing in the MRI system,which is mainly composed of scanning controller,RF transmitter,gradient controller and signal receiver.The receiver is an important part of the spectrometer.It completes the reception of imaging signals and processes digital signals.It is the step before image reconstruction,so the performance of the receiver directly affects the imaging quality.Therefore,designing a high-performance receiver which meets the requirements of MRI system is a very rewarding task.This thesis studies systematically the working principle of the spectrometer receiver,pre-scanning and image processing algorithm in the magnetic resonance system.It will elaborate the implementation method of the receiver,and describe the relationship between image quality and design method in detail.The new digital receiver of spectrometer is based on the PXIe architecture,using the National Instruments four-channel receiver adapter module NI-5761 and the FlexRIO FPGA module PXIe-7975.It can complete the FPGA code by Labview quickly.The main contents of the work include:(1)Realize the demodulation,decimation filtering.And synchronizing the phase of the receiver with the transmitter to avoid artifacts;(2)Realize the function of finding the Larmor center frequency;(3)Realize the function of looking for flip angle;(4)Realize the function of one order shimming;(5)Implement image reconstruction algorithm.Finally,the receiver designed in this paper is connected to the 1.5T MRI system of Alltech Medical System.LLC to get a water phantom image using the GRE sequence.The implementation of the receiver provides a new idea for its development.