Calibrated uncoupling of tightly coupled concentric surface coils forin vivo NMR

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Abstract
Three known active methods of detuning rf coils have been tested by determining the efficiency of uncoupling two concentric transmit surface coils in a double‐coil probe. In a comparison at 80 MHz, the method based on the use of δ/4 cables was found to have advantages. These methods utilize the introduction of an additional resonance at the frequency of interest to completely detune a coil. By offsetting the detuning of the coil (by offsetting the additional resonance) a calibrated fraction of the rf field of the detuned coil can be added to or substracted from the rf field of the neighboring coil. © 1988 Academic Press, Inc.