Improved Interleaved Single-Shot Z-Shim EPI Via Spatial & Temporal Encoding

W. Scott Hoge¹, Hong Pan¹, Huan Tan², Emily Stern¹, Robert A. Kraft²

Echo planar imaging often suffers from signal dropout in regions with high susceptibility. This is particularly problematic for fMRI studies of the brain near the nasal sinuses. Z-shim methods are one approach to recover this lost signal, where a z gradient is employed prior to the EPI readout to counter phase accumulation in the signal dropout region. Single-shot z-shim methods give improved temporal resolution, but with a cost of longer echo trains, which increases geometric distortion. Here, we employ parallel MR imaging (pMRI) to shorten the EPI echo train in a single-shot z-shim method. Temporal encoding complements the approach, to counter Nyquist ghost effects and improve the pMRI calibration. Temporal signal stability is shown to be comparable to a two-shot z-shim method.