The Design Of Multi Channel Digital Spectrometer

In the Magnetic resonance imaging(MRI) system, the spectrometer is the core component of the whole system. The major function of spectrometer is to achieve the function of MRI scan in which both a radio frequency and gradient pulse are generated, and also the magnetic resonance signals get received and processed in the particular timing according to the requirements of the imaging pulse sequence. The performance of spectrometer directly affects the quality of imaging. At present, the home-build spectrometer equipment mainly relies on imports. Therefore, the spectrometer’s independent research and design is of great significance to the development of MRI technique.Based on the analysis of the spectrometer system requirements, the paper fulfills the overall design of the whole frame and the key modules design of hardware and software of the spectrometer system. And the simulation experiments test and verify the feasibility of the program. The main content of the paper is as follows:1. This section analyzed the function and structure of the spectrometer in imaging spectrometer system Spectrometer system is divided into several modules-controlling software, scanner controller, gradient generator, radio frequency generator, radio frequency receiver etc. And we completed the design of the overall scheme of the spectrometer system by picking up some IC chips(ARM, FPGA, DSP, ADC, DAC etc) as the core chip of each module based on the features of those modules.2. This section analyzed the function of the multi-channel digital spectrometer hardware systems, and proposed the designing scheme of hardware system based on its performance.The part includes in the selection of ARM microprocessor chip and Linux system, the construction of Linux system and microprocessor, the designs of pulse sequence controller, the gradient waveform generator, and RF generator and RF receiver. We achieved the separation of software system and hardware system of spectrometer by embedding Linux system on the microprocessor ARM.And we realized a data transmission based on the ARM’s specialty of external storage and the structure of dual port RAM written on FPGA, and on this basis, we completed the multi-channel design.3. This section analyzed the function of the spectrometer software systems, and carried out its sub-module design in accordance with the functional requirement, including in the module of patient management service, the module of the scanning control pulse sequence and parameter setting system, the module of system setting, and The communication module of control software and spectrometer hardware system. Spectrometer software system programs language on the VS2010 by the use of C / S structure and C #.NET, and by the adoption of SQL Server 2005 as the database system, we accomplished the delivery of imaging scan sequences and the reception of MRI data.4. After repeated experiments and debugging, we finally completed part of the manufacture of spectrometer. Also we achieved the basic scanning process of spectrometers, which is to select pulse sequence on the spectrometer software system, which transfers the pulse sequence to the microprocessor ARM, on which we parsed sequence and transmitted it to pulse timing controller to drive gradient chip to generate a gradient signal, and at last we sent the state of the sequence which had been scanned back to the host computer software system by ARM.