Peripheral doses in modulated intensive radiotherapy (MIRT) and its implications in radiological protection

A calculation model based on the theory of photon transport, to estimate the peripheral energy fluence (fluence occurring outside the radiation beam) produced by the dispersions of photon compensating filters used was developed in IMRT mode, in a treatment room radiotherapy service of FUESMEN. In order to validate the model were experimentally determined fluences and peripheral dose for three different sizes of compensating filters. It was found that there is a slight systematic overestimation model with respect to experimental results. The experimental values also allowed the comparison of the peripheral doses with other modalities. Furthermore, a model was developed to estimate the annual dose that occurs at any point to be protected with a shield, from the theoretical values obtained from peripheral energy flow. Using the theoretical values automatically allowed to take a conservative approach because of the slight overestimation already mentioned, the couple have a calculation model for widespread use. It was found that the contribution of the peripheral dose to the annual dose is more than significant, thus suggesting that the same should be considered in the design calculations of secondary barriers