The PMOD VOI functionality supports the easy generation of regular geometric objects. They are helpful for 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 (Analytic Object) and the SPHERE (Analytic 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 an which also gives access to the VOI properties.
Create New VOI creates an new VOI with the defined properties in the VOIs list, whereas Apply replaces the definition of the currently selected entry in the VOIs list.
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 dialog window contains Location and Size fields for the exact object specification. If the box for proportional is checked (Cube in the illustration above), only one size field is shown. The Create New VOI button generates a new VOI in the list with the specified sizes, while the Apply button overwrites the currently selected VOI. The illustration below shows an example result with a 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.
Regular Contour VOIs
The non-analytic regular VOIs are formed out of planar polygons. The example SPHERE (Contour 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 in the same way as normal contour VOIs. For instance they can be scaled within the definition (axial in the example) plane, but not in the other dimension.