Accuracy of Coupled Monte-Carlo/Next-Event-Estimator for Bremsstrahlung Dose Predictions

The accuracy of an efficient hybrid Monte Carlo/ analytic method for predicting the spatial dependence of x-ray energy deposition in common dosimetry is determined by comparing its predictions with those of full Monte Carlo Transport. For x-ray simulators, the hybrid model underpredicts energy deposition in thermoluminescent dosimetry by failing to account for Compton buildup and overpredicts deposition in gold calorimetry by failing to account for the lack of electron equilibration and fluorescence escape. For gamma simulators, the method accurately predicts the deposition in thermoluminescent dosimetry. We also find that the 2.16-mm Al electron equilibrators used with our standard thermoluminescent dosimeters are excessive for x-ray simulators and insufficient for gamma simulators.