2016 年 33 巻 3 号 p. 48-56
This study was aimed to develop a framework for estimating four-dimensional （4D） dose distributions during stereotactic body radiation therapy （SBRT） based on a 2D/3D registration with an adaptive transformation parameter （ATP） approach. The 4D dose distributions during treatment delivery in the SBRT were estimated by applying a dose calculation algorithm to simulated 4D-computed tomography （CT） images during treatment time. The simulated 4D-CT images during treatment time were calculated by registering 3D planning CT images to 2D electronic portal imaging device （EPID） dynamic images through portal dose images for all frames. Transformation parameters of the 2D/3D registration were optimized by using a Levenberg-Marquardt algorithm with the ATP approach. Ten lung cancer patients who underwent the SBRT （total EPID frames : 183） were applied to this study. Mean gamma pass rates （3 mm/3%） for ten cases with and without the ATP approach were 96.10% and 94.61%, respectively （p>0.05）. The framework with the ATP approach was able to significantly reduce computational time （48.40 min） by 70.92% of that in the framework without the ATP approach （166.44 min） in all cases. Therefore, the framework with the ATP approach would be more efficient for estimating the 4D dose distributions while keeping precision in the gamma pass rates.