ABSTRACT:The application of nuclear magnetic resonance spectroscopy in metabolic studies usually includes concurrent operation at two different frequencies to enable excitation and detection of two different nuclei. When using separate radiofrequency coils for the multinuclear excitation, coupling between the two coils has been shown to be a problem, resulting in resonance frequency shifting and reduced sensitivity of the 1 H coil. Among the methods to reduce this coupling is the placement of an 1 H trap on the second-nuclei coil. This article presents the benefits of this method, specifically in this case for 31 P imaging/spectroscopy, through modeling results, bench measurements, imaging, and spectra acquisition. The use of a resonant trap in conjunction with a modular design permitted the insertion of the phosphorus coil as an ' 'add-on' ' into multiple existing proton coils, suggesting particular applicability in the high-field arena, where spectroscopy holds great promise, but where proton coil design complexity exists that is not easily re-engineered for dual-nuclei use.