Permanent implantation of 125I sources in the prostate: radical limits of simplicity.

Abstract

To determine the effect of reducing the number of sources per implantation on the dose coverage of the prostate volume. 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. 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. It is theoretically possible to radically simplify implantation without compromising target coverage or error tolerance.