Ionizing radiation is present all around us; exposure to background radiation from cosmic rays and naturally occurring isotopes is unavoidable. We are exposed during diagnostic and therapeutic medical procedures and in certain occupations. Radiation therapy for cancer allows for precise, focused delivery, with improved quality of life; nonetheless, some exposure of normal tissue is unavoidable. As a result, many millions of cancer survivors will live for decades but will bc at risk for adverse consequences such as tissue atrophy and secondary tumors (1).
Further, the devastating events of 11 September 2001 underscore the potential for radiation exposure from nuclear and radiological terrorism, which could result in large-scale casualties from improvised nuclear devices or nuclear weapons (2-4).
The acute radiation syndrome (ARS) occurs after whole-body exposure to radiation doses greater than 1 Gy. ARS is categorized into syndromes named for the organ system showing the most prominent symptoms. The central nervous system is affected within hours of exposures of more than 15 Gy, and fatalities occur within about 2 days. Gastrointestinal effects occur within a week after doses of 8 to 12 Gy; with only supportive care, most casualties will die within 10 days (4). After doses of 1 to 7 Gy, the hematopoietic (also lymphatic and immunologic) system syndrome appears in weeks to 2 months. Survival is likely at the lower end of this range and may be possible at the higher end with administration of cytokines, antibiotics, and fluids and electrolytes (4).
Radiation causes injury of normal tissue by a dynamic, evolving process involving cell killing, altered cell-to-cell communication,...