Comparison of experimental and calculated dose distributions. Electron beam dose planning at the M.D. Anderson Hospital.

An algorithm for inhomogeneity correction of electron beam dose distributions has been developed at M. D. Anderson Hospital and Tumor Institute. The algorithm uses a pencil beam calculation model to correct for air gap, tissue inhomogeneity and field shape. Computed tomography data provide surface contour and tissue inhomogeneity information. The accuracy of the calculation model has been confirmed by TLD measurements in tissue substitute phantoms reconstructed from CT patient scans and is within +/- 4 per cent or +/- 4 mm. This algorithm is currently in clinical use in selected patients with head and neck disorders. A variety of clinical examples demonstrate the effect of tissue inhomogeneity on electron beam dose planning.