ADVANCES IN 3-DIMENSIONAL RADIATION TREATMENT PLANNING SYSTEMS - ROOM-VIEW DISPLAY WITH REAL-TIME INTERACTIVITY

Purpose: We describe our 3-dimensional (3-D) radiation treatment plann ing system for external photon and electron beam 3-D treatment plannin g which provides high performance computational speed and a real-time display which we have named ''room-view'' in which the simulated targe t volumes, critical structures, skin surfaces, radiation beams and/or dose surfaces fan be viewed on the display monitor from any arbitrary viewing position. Methods and Materials: We have implemented the 3-D p lanning system on a graphics superworkstation with parallel processing . Patient's anatomical features are extracted from contiguous computed tomography scan images and are displayed as wireloops or solid surfac es. Radiation beams are displayed as a set of diverging rays plus the polygons formed by the intersection of these rays with planes perpendi cular to the beam axis. Controls are provided for each treatment machi ne motion function. Photon dose calculations are performed using an ef fective pathlength algorithm modified to accommodate 3-D off-center ra tios. Electron dose calculations are performed using a 3-D pencil beam model. Results: Dose distribution information can be displayed as 3-D dose surfaces, dose-volume histograms, or as isodoses superimposed on 2-D gray scale images of the patient's anatomy. Tumor-control-probabi lities, normal-tissue-complication probabilities and a figure-of-merit score function are generated to aid in plan evaluation. A split-scree n display provides a beam's-eye-view for beam positioning and design o f patient shielding block apertures and a concurrent ''room-view'' dis play of the patient and beam icon for viewing multiple beam set-ups, b eam positioning, and plan evaluation. Both views are simultaneously in teractive. Conclusion: The development of an interactive 3-D radiation treatment planning system with a real-time room-view display has been accomplished. The concurrent real-time beam's-eye-view and room-view display significantly improves the efficacy of the 3-D planning proces s.