Fig. 1.

Mask making algorithm flowchart. The main steps for the mask making algorithm are given. There are three steps that require a yes/no response to decide how to proceed. Steps 3 to 4 represent the iterative process for closing the outer edge of the phantom. Steps 5 to 6 represent the iterative process for filling the mask. The first step requires a selection of a radius r₁ such that it is much smaller than the radius of the phantom (r₁ = 30 voxels as per ccROI). The threshold values, th_min and th_max, consist of minimum and maximum expected number of voxels in the mask (see text to compute these). The number of voxels in the mask, n_mask, is computed at Steps 3 and 6.