Diffusion-weighted magnetic resonance imaging in Alzheimer's disease

Diffusion-weighted imaging (DWI) is a powerful new magnetic resonance imagi ng technique for evaluating tissue pathophysiology in vivo, We performed DW I in three orthogonal spatial directions in 10 patients with mild to modera te Alzheimer's disease (AD) and 11 control subjects. Average apparent diffu sion coefficients (ADCavg) were calculated for gray matter regions, and ani sotropy indexes were calculated for white matter regions. Global measures o f atrophy and white matter hyperintensities (WMH) were obtained on T-2-weig hted images to control for their potential confounding effects on ADCavg an d anisotropy, The measures of atrophy and WMH differed between the groups a nd were used as covariates in the subsequent statistical analyses. Patients with AD demonstrated diminished anisotropy in the posterior white matter ( p < 0.0001) and increased ADCavg in the hippocampus (p < 0.05) when compare d to the control group. Diffusion measures did not correlate with the sever ity of dementia, DWI provides a unique, quantitative parameter that may be sensitive to the pathophysiological and/or microstructural abnormalities th at occur in AD.