The PMOD VOI functionality supports the easy generation of regular geometric objects. They are helpful for easily creating bounding boxes and for statistics based on regular objects like spheres of a certain size rather than free-form contours.
Regular VOIs can be generated using the multi-function button illustrated below.
The list contains two sections. The CUBE (Object) and the SPHERE (Object) are based on an analytical definition of the shape and the center coordinate. The other VOIs are generated from an analytical description, but the result is a set of standard outline contours.
The regular objects are defined by the center location as well as some shape-dependent parameters. These definitions can be modified in a dialog window which is shown if the box indicated in the illustration above is checked. If it is not checked, the standard shape parameters will be applied. There are two modes for the center Location defined by the / toggle. In the position the location is defined by the last click into the image. In the position the location is not changed by mouse clicks. Activating Yes finally creates the object.
The shapes can be scaled, so that ellipsoids of arbitrary sizes can be created from a SPHERE (Object), and cuboids from a CUBE (Object). The illustration below shows an example sphere object.
To change the location and size of the object please ensure that the VOI Action button is active , so that the handles for object manipulation are shown. The center of the object can then be dragged by the central handle with the left mouse button, and the shape can be scaled by dragging the sides or the corner of the bounding box in any direction. Note that holding the SHIFT key during dragging will maintain the aspect ratio in two dimensions. The result is an object with the shape of an ellipsoid.
The non-object regular VOIs are formed out of planar polygons. The example SPHERE (VOI) illustrated below has been created with the axial plane active. Therefore circular contours were generate in the axial planes which together form a sphere. Such VOIs can be edited as normal contour VOIs. For instance they can be scaled within the definition (axial in the example) plane, but not in the other dimension.