Three possible methods for inserting volumetric ROIs
LabelRois - This is a straightforward but logistically cumbersome way of placing volumetric ROIs in tkmedit.
SegmentationRois - A more useful method for those interested in repeatedly placing multiple ROIs in a particular volume.
LineWriterHelperRois - A newer dev tool that allows for sequentially numbered ROIs with a customizable stem. A drawback is these ROIs are only linear, with a one-voxel line width.