James A. Purdy, PhD

Three-dimensional (3D) image-based treatment planning and new delivery technologies have spurred the implementation of external beam radiation therapy techniques, in which the high-dose region is conformed much

Several developments are combining to move radiation oncology into a new era--the 3-dimensional conformal radiation therapy (3-D CRT) era. Modern imaging technologies provide a 3-D view of the cancer patient's anatomy that allows the radiation oncologist to more accurately identify tumor volumes and their relationship with other tissues. The power and reliability of computers continues to increase rapidly while the costs continue to decrease. These advances have spurred the development of CT-simulation/3-D radiation treatment planning systems that are the cornerstones of the 3-D CRT era [1-3].