Implications of Computed Tomography for Inhomogeneity Corrections in Photon Beam Dose Calculations

Abstract
Patient inhomogeneity information is investigated for use in radiotherapy planning. Absorbed doses measured in a phantom are compared to doses calculated for photon beams using various treatment planning inhomogeneity correction methods. Delineation of inhomogeneities with a spatial resolution of 5 mm and with an electron density accuracy of 2% is usually sufficient to allow doses to be calculated with a mean accuracy of better than 2% for 60Co and 3% for 25-MV x rays if the authors' Equivalent Tissue—Air Ratio Method is used.