Toward Faster MRI

Parallel imaging using multiple radiofrequency (RF) coils has considerably enhanced the performance of magnetic resonance imaging (MRI).For example, SMASH and SENSE, acronyms for simultaneous acquisition of spatial harmonics and sensitivity encoding, respectively, are two widely used imaging techniques where imaging time has been reduced without significant sacrifice in the signal-to-noise ratio (SNR). In particular, SENSE uses the pixel sensitivity of receiver coils to decouple the overlapping images formed as a result of reducing the field of view (FOV). The SNR for the reduced FOV is related to g, defined as a `geometric factor' calculated from the coil sensitivities and their noise. Knowledge of the g-factor provides an SNR estimate for a given array of coils. We present the calculation of the set of g-factors for a square pinwheel coil with four loops surrounding a small decoupling loop. This coil has previously been shown* to have four completely degenerate frequencies for the four loops. * T.P. Eagan et al., BAPS, Ohio Section Meetings 2002 (Youngstown) and 2001 (Columbus State).