The use of a multi-leaf collimator for conformal radiotherapy of carcinomas of the prostate and nasopharynx.

We investigate the use of a multi-leaf collimator for conformal radiation therapy of carcinomas of the prostate and of the nasopharynx. Following verification of dose calculation algorithms for multi-leaf collimated fields using film dosimetry, we compute dose distributions for multi-field conformal treatment using fields shaped with either the multi-leaf collimator or conventional cerrobend blocks. We compare the two sets of treatment plans using graphical isodose displays, tissue specific dose volume histograms, tumor control probabilities, and normal tissue complication probabilities. We also incorporate setup errors into the calculated dose distributions to assess the effect of treatment uncertainties on the various criteria. Based on these comparisons, we conclude that for multi-field conformal radiotherapy for these two disease sites, the use of multi-leaf collimation is equivalent to that of conventional cerrobend blocks.