In current practice, radiation therapy planning (RTP) has often been treated as a two-dimensional (2D) problem, mainly due to the limitations in visualization technology and resources. The slice-by-slice display format makes it difficult to visualize the path of any radiation beam not perpendicular to the axis of the CT slices. This drawback also discourages consideration of all treatment plans that utilize radiation beam out of the transverse plane. Human body anatomical structures are inherently 3D objects, and the tumor and tissues/organs involved in the RTP are all of 3D shapes. A clear understanding of 3D relationships among these structures as well as dose distributions in 3D is essential for designing and evaluating radiation therapy plans. An interactive volumetric 3D display would significantly enhance the safety and speed of RTP procedure. It would offer "understanding at a glance", which is necessary to keep clinicians from becoming bogged down in endless details, as they would be if provided only with conventional 2D display of CT slices with overlaid isodose lines. Genex Technologies, Inc. has recently made an important breakthrough in the high-resolution volumetric 3D display technology and attempted to apply it to RTP applications. By "volumetric 3D display", we mean that each "voxel" in the displayed 3D images locates physically at the (x, y, z) spatial position where it supposed to be, and emits light from that position to form real 3D images in the eyes of viewers. In our Phase 1 project, we have demonstrated the feasibility of our system design and achieved a multi-color, large display volume, true volumetric 3D display system with an unprecedented high resolution of over 10 million voxels in a portable design. The prototype of this true 3D display system is already able to present dynamic interactive volumetric 3D images of a patient's anatomy with transparent skin. The powerful 3D visualization capability provides both physiological and psychological depth cues to oncologists in perceiving and manipulating radiation beam configuration in true 3D fashion, thus offering a unique visualization tool to ensure the safety, effectiveness, and speed of the RTP process. In our Phase 2 program, we will further enhance the performance of the volumetric 30 display, integrate the newly developed 3D display capability into the 'Interactive RTP Environment" prototype, and perform preliminary pre-clinical evaluation on the effectiveness of the volumetric 3D display and the interactive RTP environment technique in realistic RTP applications. The ultimate goal of this SBlR program is to develop a clinically viable commercial product as an augmented visualization tool that will provide unique 3D display and visualization capability to aid oncologists in RTP.