Evaluation of Inhomogeneity Correction Performed by Radiotherapy Treatment Planning System

Human body is made up of various tissues and cavities with varying physical and radiological properties, the most important of which are the lungs, oral cavities, teeth, nasal passages, sinuses, and bones in terms of radiation dosimetry. Tissue inhomogeneity affects the radiation dose distribution, and as external beam radiotherapy (EBRT) treatments become more conformal, the risk of a geographic miss due to insufficient isodose coverage around the target increases (AAPM report 85., 2004). Modern techniques, such as intensity modulated radiotherapy (IMRT), not only require an accurate dose calculation algorithm, such as the Monte Carlo, but also rely on the accuracy of Hounsfield Unit (HU) calibration prior to dose calculations for inhomogeneity corrections (especially in lung cases). Kilo voltage (kV) computed tomography (CT)-based inhomogeneity correction begins with accurate CT to HU calibration, which also requires the accuracy of HU versus electron density (ED) Abstract