Multi-Channel, Frequency-Agnostic, Portable Receiver Design for Magnetic Resonance Imaging and Spectroscopy

Abstract

Despite great potential, non-^1H magnetic resonance imaging and spectroscopy (MRI/MRS) studies have not been adopted into standard clinical use. This is largely because the signals generated by non-1^H nuclei have limited signal-to-noise ratio (SNR) due to the nuclei’s lower Larmor frequency and lower relative abundance. Exploiting the increased SNR provided by array coils is a natural direction to turn in addressing this; however, it is highly unusual for scanners to be equipped with multi-channel, multi-nuclear receivers due to cost and complexity. This leads to a “chicken or the egg” conundrum where scanners are not equipped with second-nuclei receivers because of the lack of any current widespread clinical adoption of second-nuclei studies, but studies are rare because there are not readily available receivers. The application of frequency domain multiplexing (FDM) to MRI has been investigated as a low cost alternative to expensive multi-channel receivers, and has been applied to non-^1H nuclei.

This dissertation describes the work done on a six channel, inexpensive, frequency domain multiplexed receiver, agnostic to the nuclei of interest or magnetic field strength, and implemented using off-the-shelf products. The receiver is designed to be portable and easily used in conjunction with any system with two programmable trigger lines. In addition, the architecture is straightforwardly scalable to 16 channels at an additional cost of approximately $1300 per channel. This work describes the receiver architecture and compares its performance to a commercial Varian Inova system. The flexibility and portability of the receiver are demonstrated by application to multiple channel imaging and spectroscopy of various nuclei at different field strengths, and on different scanners in different locations.