- Patients who have received maximally allowed doses (given in 2 Gy fractionations, or equivalent) of previous radiation therapy to various organs as follows: * Mediastinum: adult -40, pediatric (=<18 yrs) - 21 * Heart: adult 36, pediatric - 26 * Whole lung(s): adult - 12, pediatric - 10 * Small bowel: adult - 46, pediatric - 40 * Kidneys: adult - 12, pediatric - 10 * Whole liver: adult - 20, pediatric - 20 * Spinal cord: adult - 36, pediatric - 36 * Whole Brain: adult 30, pediatric - 30