Editing effects can be applied to the data on a 3D or slice-by-slice basis. The slice-by-slice editing can be administered on either axial, coronal, or sagittal slices simply by clicking on the appropriate slice. Each effect may be applied to either the original volume, or a working volume. Multiple editing effects may be applied to the working volume, and when finished, the working volume may be merged with a composite volume to overlay smaller structures onto larger ones.

For example, we segment skin automatically from an MR scan by applying a threshold at the first trough of the histogram (where the noise and signal lobes overlap) and storing the binary output in the working volume. We then remove islands in the working volume, and finish with an erosion and dilation to smooth the edges. This working volume is then copied to the composite volume. Next, segmentation of the brain can be performed in the working volume, and all non-zero voxels of the working volume can overwrite the composite volume to form a combination of skin and brain.

A strength of our system is that effects can be visualized by overlaying the working volume translucently on the original volume and explored in the 3D view.