Fig. 2
Main processing steps for computation of refined outer SAT (a-d, left column), refined inner SAT (e-h, middle column) and crude (envelope) VAT boundaries (i-l, right column). (a) adaptive threshold mask of MR image using adaptthresh (Matlab function) with filter size 19 × 19. (b) binarized MR image using imbinarize and mask from a. Resulting white areas primarily reflect adipose tissue but artefacts are present as well, most notably, at the bottom of the image. (c) largest connected white-pixel region from b determined using regionprops is considered as SAT. Further criteria were implemented for consistency, for example, the ratio of the principal diameters of considered regions. (d) resulting outer (yellow) SAT contour computed using bwboundaries on filled mask (not shown here) and overlaid on original MR image. (e) adaptive threshold mask with 17 × 17 filter used for binarization and (f) resulting binary mask (inverted). (g) largest connected region of mask f after multiplication with filled mask for outer SAT contour. (h) resulting inner (blue) SAT contour. (i) filled mask for inner SAT contour after evaluation of different threshold masks and quantitative criteria (region size and eccentricity). (j) eroded mask from i and (k) resulting envelope (red) boundary for VAT. (l) MR image annotated with all boundaries.
