RESUMO
The heterogeneous composition of the human body presents numerous tissue types and cavities with widely differing radiologic properties. The aim of the present work was to develop a low cost homogeneous and heterogeneous phantom and the absorbed dose were measured by ionization chamber for different radiotherapy treatment techniques and compared with treatment planning system absorbed dose values. Present work deals with the fabrication of inexpensive homogeneous and heterogeneous tissue equivalent slab phantom using polymethyl methacrylate, cork, teflon and perspex as a tissue, lung, spine and tumor simulating materials respectively. These phantoms were used for different treatment techniques and full rotation techniques in SSD and SAD techniques. The measured dose values for the different positions of both phantoms were compared with the TPS values. The values are coinciding with each other and the percentage of deviation varies from 0.47 to 2.8 and 0.49 to 2.86 for heterogeneous and homogeneous phantoms respectively. The measured values from ion chamber were compared with 3-D Plato Treatment Planning System [TPS]. TPS values were also revealed the same result for homogeneous and heterogeneous phantoms. The dose value of tumor is found to be gradually decreased with increase in arc angle. The dose value of spine is also found to be gradually decreased up to 90° and increased in 360°. Heterogeneity correction would definitely improve the cancer treatment of the heterogeneity region. This in-house phantom is inexpensive, easy to handle and very useful one to verify the TPS calculation