INTERACTIVE SEGMENTATION OF CEREBRAL GRAY-MATTER, WHITE-MATTER, AND CSF - PHOTOGRAPHIC AND MR-IMAGES

Digital photography of postmortem brain slices was compared with magne tic resonance imaging (MRI) for morphological analysis of human brain atrophy. In this study, we used two human brains obtained at autopsy: a cognitively defined nondemented control (70-yr-old male) and a demen ted Alzheimer's disease (AD) subject (82-yr-old female). For each of t wo brains, interactive manual image segmentation was performed by two observers on two image sets: (a) four coronal T1-weighted MR images (5 mm slices); and (b) four digitized photographic images from comparabl e rostrocaudal levels. Microcomputer image analysis software was used to measure the areas of three segmented cerebral compartments-gray mat ter (GM), white matter (WM) and CSF-for both image types. Resegmentati on error was defined as the absolute difference between the areas deri ved from two segmentation trials divided by the value from trial 1 and multiplied by 100. This yielded the percent difference between the ar ea measurements from the two trials. We found intra-observer agreement was better (error rates 1-18%) than inter-observer agreement (3-70%) with best agreement for WM and least for CSF, the smallest object clas s. MRI overestimated GM area relative to digitized photographs in the control but not the AD brain. The results define limitations of manual image segmentations and comparison of MRI with pathologic section pho tographic images.