New Spatiotemporal Approaches for Fully Refocused, Multislice Ultrafast 2D MRI

PurposeSingle-scan multislice acquisition schemes play key roles in magnetic resonance imaging. Central among these ultrafast experiments stands echo-planar imaging, a technique that although of optimal sampling is challenged by T-2* artifacts. Recent studies described alternatives based on spatiotemporal encoding (SPEN), which are particularly robust if implemented in a full-refocusing mode. This work extends this modality from the single-slice acquisitions in which it has hitherto been implemented, by introducing a variety of multislice schemes scanning 3D volumes. MethodsMultislice SPEN employing either inversion or stimulated echo pulses and timed to fulfill the demands of full refocusing, are demonstrated. The performance of the ensuing methods was examined in Hybrid modalities encoding data in k- and direct-space, in low-specific absorption rate stimulated-echo approaches, and in direct-space SPEN approaches. ResultsWhen applied in phantoms and in in vivo systems, the ensuing single-shot sequences evidenced similar robustness, sensitivity, and resolution qualities as previously discussed 2D single-slice schemes, while enabling a rapid sampling of the third dimension via multislicing. ConclusionThe unique benefits deriving from fully refocused, multislice, single-scan SPEN sequences were corroborated by phantom tests, as well as by in vivo scans at 3 and 7 T. Low specific absorption rate multislice SPEN variants compatible with human studies were demonstrated. Magn Reson Med 71:711-722, 2014. (c) 2013 Wiley Periodicals, Inc.