Rotating field gradient (RFG) MR offers improved orientational sensitivity

Rotating field gradients (RFGs), generated by simultaneously applying sine- and cosine-modulated gradient waveforms along two perpendicular directions, provide an alternative diffusion sensitization mechanism for magnetic resonance imaging and spectroscopy. Two RFGs with a 90-degree phase shift between them are applied around the 180-degree RF pulse in a spin echo sequence to measure the diffusion orientation distribution function (dODF) directly. The technique obviates transforming the data from a space reciprocal to the displacement space. Here, we compare RFG results with those obtained by two pulsed field gradient (PFG) techniques: q-ball imaging (QBI) and its extension to constant solid angles (CSA). Our results indicate that RFG provides more accuracy than QBI, while the spurious peaks encountered with the QBI-CSA approach are absent when the RFG-based technique is used. These observations suggest the superior performance of RFG-based methods for mapping the anatomical connections within the nervous system.