A study for the development of a low density heterogeneous phantom for dose verification in high energy photon beam

To fabricate a cost effective low density heterogeneous phantom with the combination of racemosa wood and Poly (methyl methacrylate) (PMMA) for dose verification in the high energy photon beam. The use of solid tissue equivalent material for dose verification is a well accepted and common practice for dosimetric studies. The measured Hounsfield units (HU), relative electron density, mass density were −776.6 ± 72.4, 0.223 ± 0.072, 0.202 ± 0.073 g/cc and 168.4 ± 35.3, 1.133 ± 0.017, 1.124 ± 0.021 g/cc for racemosa and PMMA respectively. The measured mass density for racemosa and PMMA were comparable to the value reported in literature for lung density (0.2–0.5 g/cc) and muscle tissue (1.059 g/cc). Depth of isodose curves of 80%, 75% and 70% were less in the uniform density of PMMA phantom, in comparison to heterogeneous PMMA-Wood-PMMA (PWP) fabricated phantom, due to less attenuation of photon beam in racemosa wood. Average percentage difference between ion chamber measured dose and AAA calculated dose was within ±3%, but the difference was higher for low density PWP heterogeneous phantom in comparison to the uniform density PMMA homogeneous phantom for patient specific QA. Results indicate that PWP phantom warrant more precise information regarding the dose deposition. Therefore, based on the measured properties of racemosa/PMMA and dose deposition patterns of photon beam in PWP heterogeneous (low density) phantom, it was concluded that racemosa and PMMA can simulate the lung and muscle tissue of thoracic region in a human body. This phantom will certainly enhance the practice of patient specific QA for lung cancer patients, treated using high energy radiation beam. •A physical phantom was constructed using the combination of racemosa wood and PMMA.•Radiological and physical properties of racemosa and PMMA were studied.•Photon dose verification was done using ion chamber in a fabricated phantom.•Phantom was used for patient specific quality assurance for cancer patients in radiation therapy.