Optimization of radiation therapy, IV: A dose-volume histogram reduction algorithm.

A general formalism for estimating the complication probability for non-uniform irradiation of a normal tissue structure has been developed and used by the NCI-sponsored committee on "Evaluation of Treatment Planning for Particle Beam Radiotherapy." The approach involves reducing an N-step dose-volume histogram for the tissue (obtained from the 3D treatment plan) to an equivalent (N-1)-step histogram; this procedure is repeated until there remains a single-step histogram, the complication probability of which can readily be determined. This note provides technical details concerning the histogram-reduction algorithm. Results obtained using it are compared with those for two alternative histogram-reduction algorithms.