Design of homogeneous and heterogeneous human equivalent thorax phantom for tissue inhomogeneity dose correction using TLD and TPS measurements

Background: The purpose of this study is to fabricate inexpensive in-house low cost homogeneous and heterogeneous human equivalent thorax phantom and assess the dose accuracy of the Treatment Planning Systems (TPS) calculated values for different lung treatment dosimetery. It is compared with Thermoluminescent Dosimeter (TLD) measurement. Materials and Methods: Homogeneous and heterogeneous thorax human equivalent phantoms were fabricated using bee’s wax (density=0.99 g/cm3) as a tissue simulating material, with inserts of cork (density=0.2 g/cm3) and Teflon (density=2 g/cm3) as lung and spine simulating material respectively. Lithium fluoride (LiF) TLD capsules were irradiated for different thoracic tumor treatment techniques using the locally fabricated homogeneous and heterogeneous phantoms. The 3D TPS calculated values of homogeneous and heterogeneous phantoms were compared with TLD measured values. Results: Experiments were carried out for different thoracic tumour treatment techniques for small and larger field sizes and also with and without wedge for Cobalt – 60 photon beams. Plato TPS were used to calculate the inhomogeneity for the homogeneous and heterogeneous phantoms. TLD and 3D TPS calculated values were found to have deviation of ± 5%. Conclusion: Both the homogeneous and heterogeneous phantoms has proved to be a valuable tools in the development and implementation of external beam radiotherapy (EBRT) in the clinical thorax region and in the verification of absolute dose and dose distributions in the regions of clinical and dosimetric interest.