HIGH-RESOLUTION RENAL DIFFUSION IMAGING USING A MODIFIED STEADY-STATE FREE PRECESSION SEQUENCE

A modified steady-state free precession (SSFP) diffusion sequence is proposed for high resolution renal imaging, A pair of bipolar diffusion gradients was used to minimize the errors in measured apparent diffusion coefficient (ADC) caused by variations in T-1, T-2, and RF flip angle that have been observed with previously employed SSFP diffusion sequences, Motion sensitivity was reduced by the use of compensated gradients, frame-by-frame averaging, and a repetition time of 22 ms, which for a single-acquisition 128 x 128 image requires only 3 s. High resolution was achieved by signal averaging, The modified sequence was applied to in vivo diffusion measurements. In six normal rat kidneys the ADCs (mean+/-SD; x 10(-3) mm(2)/s) of the cortex, outer medulla, and inner medulla were 2.28 +/- 0.05, 2.38 +/- 0.10, and 2.95 +/- 0.05, respectively, The technique requires relatively large gradients to achieve adequate diffusion weighting.