A Modified sub‐second fast‐STEAM sequence incorporating bipolar gradients for in vivo diffusion imaging

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Abstract
A modified high‐speed stimulated‐echo acquisition mode (STEAM) diffusion sequence (90°‐TE/2−90°‐TM‐[α‐TE/2‐STE]n) incorporating bipolar diffusion gradients that are less sensitive to macroscopic motion‐induced artifacts is presented. Diffusion encoding was performed only during the first echo interval (TE1) with bipolar gradients that were implemented on all three mutually orthogonal axes. Calibration measurements on phantoms filled with water, isopropanol, and dimethyl sulfoxide yielded apparent diffusion coefficients (ADC) consistent with published values. Non‐ECG‐triggered in vivo images acquired on rat brain with relatively high b values (˜450 s/mm2) indicated minimal motion artifacts. Evaluated ADCs averaged over the cortex, left mid‐brain, right mid‐brain, regions yielded (0.91 ± 0.02), (1.06 ± 0.02), (1.01 ± 0.03) × 10−3 mm2s−1, respectively.