QUANTITATIVE DIFFUSION-COEFFICIENT MAPS USING FAST SPIN-ECHO MRI

In this work, we have evaluated the performance of a diffusion-sensiti ve fast spin-echo (FSE) pulse sequence, The proposed pulse sequence ut ilises velocity-compensating diffusion-encoding gradients and includes the collection of navigator echoes, Spoiler gradients were inserted i n the slice-selecting direction to minimise effects from stimulated ec hoes. Calculations of the b values showed that cross-terms between ima ging gradients and diffusion gradients only led to a marginal increase of b values. Pixel-wise calculation of apparent diffusion coefficient (ADC) maps was performed numerically, considering cross-terms between diffusion-encoding and imaging gradients, The sequences investigated used echo train lengths of 16, 8 and 4 echoes and were encoded in eith er the slice-, frequency- or phase-encoding direction. In order to all ow for higher b values a pulse-sequence version using non-motion compe nsating diffusion-encoding gradients was written, Phantom measurements were performed and the diffusion coefficients of water and acetone we re reasonable. Seven healthy volunteers (age 28-50 years) were examine d and apparent diffusion coefficient values agreed well with expected values. Diffusion-weighted images, apparent diffusion coefficient maps and images corresponding to the trace of the diffusion tensor of good quality were retrieved in vivo. (C) 1998 Elsevier Science Inc.