Design of a waveform synthesizer and data acquisition system in NMR imaging

Abstract

In nuclear magnetic resonance computerized tomography (NMRCT) there are three types of input, i.e, a static magnetic field, RF fields, and gradient fields such as Gx, Gy, and Gz. Consequent output pulse or signal is the free induction decay (FID) signal In this thesis, a waveform synthesizer which generates RF waveforms and gradient pulses and controls the data acquisition part specially designed for NMR imaging are described. The former is designed to take advantage of run length coding, thereby making waveform generation flexible and accurate. The design emphasis of the latter is focused on simultaneous operation of data aquisition and transfer of data to the host computer, VAX 11/780. Sampling rate of as high as 250 KHz in analog-to-digital conversion process with 12bits resolution is also a notable feature.