| Magnetic Resonance Imaging is an important research tool in both clinical diagnostic and scientific researches, and gains a great deal of achievements since its invention. In MRI systems, the spectrometer plays an important role. Therefore, it has great value to investigate the instrumentation techniques about the spectrometer, and this is particularly beneficial for the home-builders of MRI systems.In our laboratory, we have designed the individual units to construct a home-made digital spectrometer. Though versatile, there are still problems. This is true for the gradient and the receiver units. Accordingly, we propose a gradient waveform generator based on DSP technology, and A MRI receiver based on digital IF receiver. A detailed research is stated in this thesis, and the design method and hardware implementation will be given in detail.This thesis is divided into 3 parts:The first part briefly describes the basic theories of NMR and MRI. We also discuss about the composition of the spectrometer taking the "Digital spectrometer" designed by our laboratory as an example.The second part is concerning about the design of "A gradient waveform generator based on DSP technology",including the results of the experiment. Thanks to the employemt of the DAC with high resolutuion and high sampling-rate, this gradient waveform generator can provide exllent linearity, short rise-time and satisfying pre-emphasis effect.The third part presents the design of a multi-channel MRI receiver based on digital IF receiver technology. This design solution copies part of the signal chain, which could simplify the structure and lower the cost of the MRI spectrometer without losing the performance. As for a single receiver, it not only realizes all the functions supplied by the previous receiver, but also provides some flexible options, such as variable gains and changeable spectrometer width during a scan. This can offer hardware support for the realizations of some special pulse sequences.
|
PDF Full Text Request