Figure 2.

Example of one of the basis functions j used in the forward projection of the parameters θ. In this case, ${\theta }_j$ represents the uptake in the gray matter of the right middle front gyrus. The probability map of the middle front gyrus in the Hammersmith atlas (1) is multiplied by the gray matter mask from the classified image of the BigBrain atlas (2) to generate the column j of matrix TA (3). The latter is then multiplied by the diagonal matrix D with the cell body density of the BigBrain atlas (4) to generate the column j of matrix DTA (5). Finally, the image in (5) is smoothed to match the resolution of the template used as a reference to form column j of matrix HDTA. Images 1, 2, 3, 5, and 6 show one slice of the 3D image (which is stored as a vector in the column j of each matrix), while image 4 shows the same slice for the 3D image stored in the diagonal elements of matrix D.