[Calculation of dose distribution of fast electrons within and behind tissue inhomogeneities of any width].

A new algorithm allowing for the effects of tissue inhomogeneities on dose distributions of high-energy electrons is presented for the purposes of treatment planning computations. Starting from the electron dose distribution for homogeneous tissue the doses contributed by the partial beam hitting the tissue inhomogeneity are substituted by those arising from a partial beam which was alterated by stopping, scattering and changed distances in the inhomogeneity. Since actual data for partial beams of limited cross-section are used and the scatter contributions from the rest of the total beam into and behind the inhomogeneity remain unchanged, good approximation compared to measured values is achieved.