| The objective of my research at NEORCC is to evaluate the effectiveness of intensity-modulated radiotherapy (IMRT) using Cobalt-60. This highly conformal treatment planning and delivery technique could be applied to a vast number of countries using Cobalt-60 teletherapy if appropriate dose distributions could be generated. We know, however, that patient set-up is neither perfectly accurate nor precise, with much information on such set-up uncertainties becoming available in recent years. The perceived superiority of 6MV x-ray photons over Cobalt-60 gamma rays for the irradiation of targets in proximity of critical normal organs is largely based on the smaller penumbra achievable with bremsstrahlung sources. The impact of random and systematic patient set-up uncertainties was explored to determine the extent to which the superiority of 6MV photons is compromised when these errors are taken into account. The method used was direct simulation, which efficiently calculates the average weighted dose-volume histogram (DVH) in the range of set-up errors studied with the distribution of DVHs represented by the standard deviation about the mean dose-volume values. We describe a method of incorporating organ motion into treatment plans. The DVHs were used to express the target volume coverage, organ-at-risk (OAR), and steep-dose gradients in IMRT segments. The commissioning of intensity-modulated radiation therapy with stainless steel granulate modulating filters is presented. For this purpose, a planning comparison study between conventional treatment and IMRT using 6MV and Cobalt for the treatment of brain cancer is assessed to determine the potential benefits of IMRT. |
