Room: Exhibit Hall
Purpose: By utilizing multiple shots in Gamma Knife radiosurgery, one can improve the dose distribution (Cheek et. al 2005). Traditionally, a single shot is delivered and the radiation is suspended while transitioning to the next shot. If a high number of shots are intended to be delivered, then the transitioning time in between shots can add to the overall treatment time. The purpose of this study is to investigate the differences between a traditional delivery method versus a continuous delivery.
Methods: An optimized Gamma Knife plan was developed for a 4.3cc lesion that utilized thirteen 8mm and two 16mm shots. A traditional delivery dose distribution was calculated. For the continuous shot dose distribution, a custom program was written that determines a minimal travel path, discretizes the path in 1mm increments, and calculates the resulting dose distribution for the continuous shot movement. The two resulting dose distributions were compared.
Results: For the 15-shot plan, traditional transitioning time between shots was calculated to be approximately 46 seconds. The prescription coverage, conformality index, and gradient index for the two delivery methods was approximately identical. The target maximum doses differed by 0.4% of Rx while the target minimum differed by 0.2% of the Rx.
Conclusion: Transitioning to a continuous delivery methodology can decrease treatment time while providing a comparable dose distribution. Preliminary data indicates that the continuous delivery methodology could allow for an increased number of shots. Previous studies have shown the dose distribution can be improved by delivering a high number of shots; therefore future studies will investigate increasing the number of shots.