SUPERCONDUCTING PROBE COILS FOR ULTRA LOW-FIELD MRI

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Two types of magnetic-resonance-imaging (MRI) machines - specifically, the Picker/Nordstar Merit machine operating with Overhauser enhancement and the pulsed-field machine under development at Stanford University - will use readout field strengths less than or equal to 0.01 T. At the corresponding low readout field strengths less than or equal to 0.01 T. At the corresponding low readout frequencies (less then 400 kHz), the noise voltage generated by a 20-cm normal-metal coil is more than 18 times the tissue-generated noise. Thus, a signal-to-noise enhancement of 18 could be obtained through the use of low-noise superconducting coils. Conductus has already demonstrated superconducting coils for low-field MRI at 4 MHz (0.1T). Reaching the sub-MHz frequencies of ultralow-field MRI requires much larger inductances and/or capacitances in the tuned coil. In the proposed Phase I effort, two methods of reaching these low frequencies with high-Q coils will be examined, prototypes will be designed, and initial measurements will be made. In Phase II, coils will be delivered to the two instrument developers for evaluation.