High-temperature superconducting receiver coil for NMR skin imaging

Abstract
In NMR imaging, internal coil losses and patient-induced losses are the two dominant noise sources. Using small-sized antennas can increase the SNR when imaging small areas at the surface of the body. But this improvement is limited because the internal coil losses become dominant over the patient induced losses and set an actual limit to the SNR. The use of HTS material at low temperature with small-sized antennas should considerably improve the image quality. We describe a multi-turn transmission line resonator made from a sandwich YBaCuO-Sapphire-YBaCuO. Intrinsic parameters of YBaCuO have been determined by HF characterisation (45 MHz-45 GHz) using a network analyser. The antenna NMR-coil performances have been evaluated by RF measurements using a dual-loop technique and an dedicated cryocooler. The RF measuremens can be interpreted extrapolating the HF thermal behaviour. A gain in SNR of about 9 can be expected at the skin surface corresponding to the ultimate limit set by the patient -induced losses.