RESUMO
PURPOSE: To determine the effect of reducing the number of sources per implantation on the dose coverage of the prostate volume. MATERIALS AND METHODS: Idealized source distributions were planned for four, eight, 16, 24, 32, and 48 sources. The peripheral loading technique was used to plan a uniform, conformal dose distribution to the target volume, which was the prostate volume as visualized at ultrasonography. Source-placement error was estimated by using measured error magnitudes and was expressed with systematic and random components. The relative sensitivities of the plans to the source-placement error were studied. RESULTS: Idealized planned target coverage can be adequately achieved with comparable dose distributions with eight or more sources. The sensitivity to source-placement error is comparable for plans with 16 or more sources. CONCLUSION: It is theoretically possible to radically simplify implantation without compromising target coverage or error tolerance.
