A MODIFIED SUB-SECOND FAST-STEAM SEQUENCE INCORPORATING BIPOLAR GRADIENTS FOR IN-VIVO DIFFUSION IMAGING

A modified high-speed stimulated-echo acquisition mode (STEAM) diffusi on sequence (90 degrees-TE/2-90 degrees-TM-[alpha-TE/2-STE](n)) incorp orating bipolar diffusion gradients that are less sensitive to macrosc opic motion-induced artifacts is presented, Diffusion encoding was per formed only during the first echo interval (TE1) with bipolar gradient s that were implemented on all three mutually orthogonal axes. Calibra tion measurements on phantoms filled with water, isopropanol, and dime thyl sulfoxide yielded apparent diffusion coefficients (ADC) consisten t with published values, Non-EGG-triggered in vivo images acquired on rat brain with relatively high b values (similar to 450 s/mm(2)) indic ated 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) x 10(-3) mm(2)s(-1), respectively.