Total body radiotherapy

Total body irradiation (TBI) with megavoltage photon beam is most commonly used as part of the conditioning region for bone marrow transplantation which is used in the treatment of variety of diseases such as leukemia, aplastic anemia, lymphoma, multiple myeloma, autoimmune diseases, inborn errors of metabolism, and so on. The role of TBI is to destroy the recipient's bone marrow and tumor cells, and to immunosuppress the patient sufficiently to avoid rejection of the donor bone marrow transplant. Usually the patient undergoes a chemotherapy conditioning program before the TBI and bone marrow transplant. Although chemotherapy alone can be used as a conditioning regimen, addition of TBI is considered beneficial for certain diseases and clinical condition.

In the Radiation Oncology Department at Stony Brook University Medical Center, TBI is delivered using 21EX linear accelerator through anterior and posterior fields in a standing upright position at the TBI distance. A special treatment room is designed for large-field irradiation. The principle of the technique is that the standing TBI allows shielding of certain critical organs from photons and boosting of superficial tissues in the shadow of the blocks with electrons. Foe example, dose to the lung can be reduced using lung blocks and the chest wall under the blocks can be boosted with electrons of appropriate energy.

The radiation will be given in a hyper-fractionated schema. The total dose is to be 1,200 cGy, and the minimum number of dose fractions will be 8, given on a twice a day basis of 150 cGy per dose. The daily dose fractions should be separated by 6 hours.