April 14th 2009The ultimate goal of radiation therapy (RT) is to deliver enough radiation to eradicate all tumor clonogens within the irradiated field while also minimizing dose to adjacent normal structures so as to cause no (or minimal) normal tissue injury. With few exceptions, the dose of radiation currently delivered to most anatomic sites is limited by the tolerance of these adjacent normal organs, thereby restricting the dose of radiation deposited in tumors to an amount that may or may not be ideal to realize an optimal cure. The goal of many advanced technologies introduced into RT are aimed at addressing this problem.