Stage Four: Region Analysis and Labeling

  In Stages Two and Three, the knowledge extracted up to this point was applied to pixels individually. Stage Four, allows spatial information to be introduced by considering pixels on a region or component level.

  

Figure 9: Regions in Image Space. After processing the intra-cranial mask (a), (b) is an initial tumor segmentation. Only one region, as shown in the ground-truth image (c) is actual tumor. Region analysis discriminates between tumorous and non-tumorous regions.

Applying an eight-wise connected components operation [37] to the refined tumor segmentation generated by Stage Three, allows each region to be tested separately for the presence of tumor. An example is shown in Figure 9. After processing the intra-cranial mask shown in Figure 9(a) in Stages Two and Three, a refined tumor segmentation (b) is produced. The segmentation shows a number of spatially disjoint areas, but ground truth tumor in Figure 9(c) shows that only one region actually contains tumor. Therefore, decisions must be made regarding which regions contain tumor and which do not.