High b value diffusion-weighted imaging is more sensitive to white matter degeneration in Alzheimer's disease

It has been reported that diffusion-weighted imaging (DWI) can detect white matter degeneration in the Alzheimer's disease (AD) brain. We hypothesized that imaging of the slow diffusion component using high b value DWI is more sensitive to AD-related white matter degeneration than is conventional DWI, and therefore we studied the effects of high b value on lesion-to-normal contrast and contrast-to-noise ratio (CNR). Seven AD patients and seven age-matched normal subjects were studied with full-tensor DWI at three different b values (1000, 2000, and 4000 s/mm²) without changing echo time or diffusion time, and the mean diffusivities in the parietal and occipital regions were measured. Statistical analyses revealed that use of higher b values significantly improves both lesion-to-normal contrast and CNR. We concluded that high b value DWI is more sensitive to AD-related white matter degeneration than is conventional DWI.