Optimal b Values for Generation of Computed High-b-Value DW Images.

Abstract

The purpose of this study was to investigate the optimal b values required for the generation of computed high-b-value DW images. Brain DWI was performed for eight subjects using 16 b values, ranging from 0 s/mm(2) to 5000 s/mm(2). The fractional value as the turning point between the fast and slow components was determined using a diffusion decay curve. Image contrast in the white matter, gray matter, thalamus, putamen, and lateral ventricle was compared between the acquired high-b-value images and the computed high-b-value images derived from various b value images. In addition, the signal-to-noise ratio of each computed image and acquired image was measured and compared. The fractional values obtained from the diffusion decay curve were between 1200 and 1800 s/mm(2). Image contrast in all regions was nearly equivalent between the acquired and computed high-b-value images when b values higher than the fractional value were used, whereas image contrast was significantly different between the two sets of images when b values lower than the fractional value were used (p < 0.05). The computed images derived from low-b-value images showed a higher signal-to-noise ratio, compared with the acquired images. Optimal b values should be considered when acquiring images for the derivation of computed DW images.