Essentially, any tumor can be eradicated if the absorbed dose of radia high enough. A major limiting factor, however, is the amount of radiation that the surrounding healthy tissue can safely tolerate. The goal of radiation is achieved when the tumor is completely destroyed while the surroun ing tissues show minimal evidence of structural or functional injury. Improved delivery systems and a better understanding of radiobiological principles have to reduce the incidence and degree of radiation tissue injury. However, localized radiation damage to healthy tissue continues to occur. (12, 46, 23 The pathophysiologic sequence of radiation-induced tissue injury has been described by Berdjis(4) as four specific periods.
Acute(first six months): Organ damage accumulates. This period may be clinically silent, unless tissue-tolerance limits are exceeded.