Quantifying the impact of radiation therapy dose uncertainties on radiobiological treatment plan evaluation




Cranmer-Sargison, Gavin

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The goal of this study was to quantify the impact of dose uncertainty on radio-biological treatment plan evaluation. A formalism was developed for assessing the impact of dose uncertainty on survival fraction (SF). To distinguish between spatial and probabilistic dose variations, we define equivalent stochastic dose (ESD) as the voxel dose that gives an expected survival fraction for the randomly deposited dose. In the case where the probabilistic voxel dose follows a Gaussian distribution, we de-rive an analytic expression for SF(ESD). We show the analytic expression can account for multi-voxel dose distributions that incorporate both probabilistic and spatial dose heterogeneities. In addition, we incorporate dose uncertainty in the calculation of tu¬mour control probability (TCP) using the ESD formalism. We verify the derivation and implementation of the derived expression using the Monte Carlo method for cases of 60 Gy and 70 Gy at 2 Gy per fraction. The results show that the derived formalism is an effective method for evaluating the radiobiological impact of dose uncertainties on treatment plan evaluation.



medical physics, radiotherapy