A comparison of planned radiotherapy dose distributions calculated by Monte Carlo with variation of technique, statistical uncertainty and voxel size on resulting gamma pass rates

Abstract

Background: The gamma analysis index () is the most commonly used method to compare a calculated and measured dose distribution. A caveat to the clinical use of  is that the formalism does have a sensitivity to noise present in either distribution. Monte Carlo (MC) based dose calculation methods are widely accepted as the most accurate method to calculate a resulting patient dose distribution from a radiation therapy treatment plan [6]. However, noise is inherently present as random errors or statistical uncertainty within all MC based dose calculation methods and is inversely proportional to the dose calculation time [7]. A research experiment performed by Van Delinder et al. investigated the effect of decreasing voxel size and increasing statistical uncertainty for a Monte Carlo based dose calculation method using 10 clinical head and neck (H&N) IMRT treatment plans. The experimental result was a definitive increase in  passing rates with combined decrease in voxel size [10]. In order to further clinical information regarding this phenomenon, a large comprehensive study is required using multiple treatment techniques, a different treatment site, and using a different type of radiation measurement device.