Magnetic Resonance imaging (MRI) is now increasingly being used for fast imaging applications such as real-time cardiac imaging, functional brain imaging, and contrast enhanced MRI. Imaging speed and resolution in MRI are mainly limited by the signal to noise ratio (SNR).

SNR can be improved by reducing the thermal noise in the system which can he achieved by cooling the coils and/or using high critical temperature superconductor (HTS) coils. The SNR can be further improved by optimizing the coil design, its associated electronics, and the interface used to connect to the system. Recently, there is a great demand for imaging using coil arrays. As the number of array elements increases and the size of each element continue to decrease, the thermal noise of the radio frequency (rf) receiver coil becomes the dominant source of system noise. In such a case, significant SNR improvement can be achieved by cooling down normal metal coil or by using HTS coils.

The primary objective of this dissertation is to investigate the feasibility of reducing the thermal noise by using different designs of cryogenic, high SNR receiving coils and arrays for imaging of small animals. For imaging of small animals with high Q-factor coils both tuning the coils to the scanner's frequency and matching the coils to 50 Ω have to be controlled remotely from outside the scanner. The tuning/matching circuitry was designed and implemented using dc controlled variable capacitors (Varactors). For both single coils and coil arrays capacitive coupling to coils was a more convenient method to be implemented into the system. Capacitive decoupling was used to decouple array elements and was extensively investigated and tested.

In this dissertation, different techniques for actively decoupling the receive coils from the volume transmit coil are also investigated. The development and fabrication of a 7 T cryogenic system for a receive-only single HTS coil for rat brain and spinal cord MRI is described and followed by a demonstration of the superiority of this coil over the state-of-art commercially available coils. The developed coils were extensively tested at the University of Texas Medical School using a Bruker T scanner. A 200% SNR gain over room temperature coils was recorded confirming that an HTS coil and array can provide very substantial SNR gains nor obtainable by other techniques of SNR improvement.

The development and fabrication of a room temperature copper coil array are also presented and the resulting images are shown in this dissertation. The Sensitivity Encoding (SENSE) technique was chosen as an example for parallel imaging techniques. Software code was written in MATLAB to simulate and implement the SENSE technique on simulated and real images acquired with the coil array to obtain faster imaging.