Automated adjustment of display conditions in brain MR images: diffusion-weighted MRIs and apparent diffusion coefficient maps for hyperacute ischemic stroke.

We developed a new computerized scheme for proper display of brain diffusion-weighted magnetic resonance images (DWIs) and apparent diffusion coefficient (ADC) maps based on density histogram analysis. In our scheme, DWI volumes and b0 image volumes of 44 cases were first created, and brain regions on DWI volumes were segmented. ADC map volumes were then derived from both volumes. The density histogram was determined from the brain regions on these volumes, and the voxel value corresponding to the maximum in the density histogram was determined for each volume. The display gray level for each of the two volumes was adjusted by setting the determined voxel value as window conditions. In a comparison between the existing manual method and our automated method, the variation in the gray levels was evaluated quantitatively. The variation in the average of the cross-correlation values determined for pairs of density histograms in each of the DWIs and ADC maps was 57.3 and 27.1 % with the existing method, respectively, and 7.7 and 2.7 % with our scheme, respectively, which indicated a more consistent display of images with our scheme. The performance of the two-alternative-forced-choice method for visual comparison of pairs of images in each of the DWIs and ADC maps adjusted by our scheme was judged to be better than those of the existing method by 75.1 % and 92.7 %, respectively. Our computerized scheme would be a promising technique for an accurate, prompt automated adjustment of display conditions in brain DWIs and ADC maps.