Neutron dosimetry in a model of the body's inhomogeneities using the TLD-300 detector

The modification of the absorbed dose distribution due to the presence of inhomogeneities in the human body requires thorough research within the scope of radiation treatment planning for tumour therapy with fast neutrons. In this work the effect of air and lung cavities and the depth dose distribution in the near and distant vicinity of the inhomogeneity is studied. By means of thermoluminescence detectors TLD-300 the total absorbed dose is measured in mixed neutron-photon radiation fields in the used polystyrene phantom with embedded inhomogeneity. Lung tissue is simulated by cork. Differences in the concentration of hydrogen between inhomogeneity and surrounding soft tissue lead to new build-up effects. These cause an increase behind and a decrease of the total dose beside and in front of the inhomogeneity. In case of the cork inhomogeneity an absorbed dose increase of maximally 20% in comparison to the absorbed dose in the homogeneous phantom was found. With air as inhomogeneity the increase of absorbed dose reaches a maximum of 30% compared to the homogeneous phantom.