TRANSMIT & RECEIVE COIL FOR 1H DECOUPLED 13C OR 31P DETECTION

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An ideal coil configuration for in vivo proton decoupled NMR spectroscopy requires a highly sensitive 13C coil as well as an efficient proton decoupling coil. Ideally those coils should have very similar areas of sensitivity yet display no significant electromagnetic interaction. These goals were achieved with a new coil design that utilized the benefits of a quadrature 1H coil to reduce the power requirements up to two-fold and combined it with a linearly polarized 13C coil with negligible performance loss on either channel. Two circular 1H coil loops (12 cm diameter) were arranged to generate a quadrature field in the area adjacent to the 7 cm diameter 13C coil made from 1/4" copper tubing. Partial overlap between the 13C coil and each individual 1H coil as well as the overlap between the two 1H coils can be adjusted so as to minimize electromagnetic coupling among all the coils; this was performed while loaded on the laboratory bench with a suitable phantom (2.5l distilled water, 100 ml saline) as well as a human leg. The resulting coupling between the 13C coil and either of the 1H coil loops was less than -20 dB for various loading situations (phantom, human leg, human head). We found the achieved isolation to be sufficient for broad band decoupling without addition of further performance limiting circuit elements such as ??? lines.