1989

Viitanen, Jari

In cancer treatment radiation therapy is one of the most important treatment methods.This study discusses the development and evaluation of a new radiation therapy dose planning system.Especially, the external photon beam calculation algorithms are described.The radiation beam model of the system developed is based on tabulated depth dose and profile curves.The correction factors due to the use of wedge filters and block beam modifiers are also modelled using tabulated values.Obliquity correction is made by cal culating the ratio of tissue air ratios.Inhomogeneity correction is made by the generalized power law method or the equivalent tissue air ratio method.The system can use digital computerized tomography (CT) images as a patient model. The images are used for patient viewing and target definition, for patient contouring and for calculation of the tissue inhomogeneity correction.The dose planning system developed has been evaluated by using two photon energies of 1.25 MeV (Cobalt 60) and 14 MeV (Microtron MM14 accelerator).The evaluation has been done by comparing the results calculated by the developed system with the results of measurements and simulations.The evaluation shows that the accuracy and the performance of the system meets the clinical requirements.