Figure 7.

Evolution in the number of voxels excised from the 3D volume in XDD registration. Four levels of the morphological pyramid are evident (DS8, DS4, DS2, and DS1). The horizontal dashed line in each level marks the true number of voxels within the excision volume in the fixed image. The open circles mark the cumulative number of voxels ejected from the volume, whereas the small dots mark the (instantaneous) number of voxels ejected in a given iteration. For the nominal XDD parameters described in the text, a gradual, conservative convergence on the true excision volume is observed (without overshoot).