Validation of fast Monte Carlo dose calculation in small animal radiotherapy with EBT3 radiochromic films

International audienceIn preclinical studies, the absorbed dose calculation accuracy in small animalsis fundamental to reliably investigate and understand observed biologicaleffects. This work investigated the use of the split exponential track lengthestimator (seTLE), a new kerma based Monte Carlo dose calculation methodfor preclinical radiotherapy using a small animal precision micro irradiator,the X-RAD 225Cx.Monte Carlo modelling of the irradiator with GATE/GEANT4 wasextensively evaluated by comparing measurements and simulations for halfvaluelayer, percent depth dose, off-axis profiles and output factors in waterand water-equivalent material for seven circular fields, from 20 mm down to1 mm in diameter. Simulated and measured dose distributions in cylinders ofwater obtained for a 360° arc were also compared using dose, distance-toagreementand gamma-index maps.Simulations and measurements agreed within 3% for all static beamconfigurations, with uncertainties estimated to 1% for the simulation and 3% forthe measurements. Distance-to-agreement accuracy was better to 0.14 mm. Forthe arc irradiations, gamma-index maps of 2D dose distributions showed thatthe success rate was higher than 98%, except for the 0.1 cm collimator (92%).Using the seTLE method, MC simulations compute 3D dose distributionswithin minutes for realistic beam configurations with a clinically acceptableaccuracy for beam diameter as small as 1 mm