Comparison of experimental data with calculation results of bilateral total body irradiation using 6 MV X-rays

Total Body Irradiation (TBI), a method of radiation therapy, was investigated in this study. Bilateral radiation fields were applied by changing patient positioning in treatment. The Monitor Unit values (quantitiy of irradiation dose) were prescribed by using both hand made calculations and treatment planning system calculations. Accuracy of the estimated irradiation value was invastigated by using thermoluminescence dosimeter measurements. Contemporary treatment machines use 100 cm isocenters with a maximum field size of 40x40cm2. However, TBI treatment requires larger field sizes. To aquire the necessery field sizes the distance from patient to source is enlarged. Because of this enlargement, the changes of some dosimetric parameters should be investigated. In this study, parameters like percent depth dose, dose profile and dose efficiency were investigated for standart treatment distances and for larger distances. Dose values of the different body zones should be estimated for the given dose of two side positions of the umblicus. Dose values, were evaluated by using a treatment planning system which includes manual calculation and TBI options. Evaluated values were compared with the measurements of the TLDs. Rando phantom, which has materials similar to human tissue densities was irradiated. Besides, plexiglass material was used to increase the skin dose in TBI.