Figure 1.

Overview of infant template construction. Initially all images are registered to the adult /pediatric template. After registration a segmentation estimation procedure is used to estimate the parameters by iteratively going through segmentation (S), bias correction (BC), deformation (DF) and priors (P) until convergence criteria (C) are met. After this step two strategies are used for calculation of the tissue probability maps. The first (default) strategy includes adult prior probabilities for distribution of GM, WM and CSF based on adult / pediatric data indicated by the inclusion of the blue box (P). The second (new) strategy does not use prior probability distributions in the calculation of the tissue probability maps; instead it only uses the intensity of the T1 images. Then a Hidden Markov Random Field (HMRF) process is applied to the resulting image, normalized and averaged to produce the first pass template. Second pass templates are obtained in similar fashion except the first pass template is used for registration and normalization.

Key: DA1/DP1=First pass adult/pediatric template via default strategy;

DA2/DP2=Second pass adult/pediatric template via default strategy;

NA1/NP1=First pass adult/ pediatric template via new strategy;

NA2/NP2=Second pass adult/pediatric template via new strategy. Bold font indicates adult data while italic font indicates pediatric data.

Comparisons: 1. (g-a) and (i-a); 2. (h-b) and (j-b); 3. (g-i); 4. (g-c), (i-e) and (h-d), (j-f); using number conventions from table 2.