Display of organs and isodoses as shaded 3-D objects for 3-D therapy planning.

We have developed a technique that allows the user to assess and modify 3-D dose distributions in planning a treatment. Organs and superimposed isodoses can be displayed as shaded solid objects from any desired point of view. The graphic tools necessary are described in detail. Briefly, after the volumes of interest have been defined as contours taken from CT scans, the beam data can then be defined using the "beam's eye view" technique. Subsequently, the desired isodoses can be extracted from the three-dimensional dose matrices and displayed as a series of "barrel hoops" over the target volume. We have found this technique to be particularly useful for development of treatment plans where the spatial relationship of sensitive organs such as the spinal cord may change considerably within the treatment volume. Such a case is described in detail.