In the past few decades, the radiation oncology eld has been transformed by computers-similar to what has happened in our societies. e increase in computing power has led to better computerized treatment planning soware, enabling higher quality and more precise delivery of radiation treatments. For example, linear accelerator-based stereotactic radiation therapy (SRT) or stereotactic radiosurgery (SRS) has been made possible, not merely because of advances in head xation and beam collimation technologies but also because of improvements in soware for computer-based treatment planning and delivery. Another important development in the radiation arena is that of intensity-modulated radiation therapy (IMRT), where the uence intensity of each beam is spatially modulated and regulated (Brahme 1988; Carol et al. 1996; Webb 1992; Yu 1995). Using inverse planning algorithms, each radiation eld is broken into multiple small beamlets, allowing optimization of the radiation dose to the target and minimization of the dose to the adjacent critical tissues (Eklof et al. 1990; Kooy and Barth 1990).