Fabrication of anthropomorphic phantoms for use in total body photon irradiation and total skin electron irradiation studies

Introduction: Total Skin Electron Therapy (TSET) and Total Body Irradiation (TBI) are kinds of treatment which use electron and photon beams to treat special types of cancers. The aim of these techniques are to deliver uniform dose to the entire skin while minimizing delivered dose to organs at risk. To check the homogeneity of dose delivery in TBI and TSET, using a humanoid phantom is necessary. Aim of this study is to manufacture an anatomical model of an adult male included lower limb to evaluate the dose distribution in dosimetry measurements of radiotherapy. In addition, we want to offer a method for low-cost fabrication of an anthropomorphic phantom by tissue substitute material compared to similar commercial phantom.
Materials and Methods: To design the phantom, CT scan images of the atomic energy organization RANDO phantom were our reference. Also AutoCAD, Corel and Solid works software were used. This Phantom has five different heterogeneities including air, Plexiglas for Soft tissue substitute, Polytetrafluoroethylene (PTFE) for Bone tissue substitute, Cork for Lung tissue and Polyethylene for designing three organs such as rectum, bladder, and prostate and also has four sections including head and neck, trunk, pelvis and two legs. After construction, the phantom was validated by CT number conformity and relative electron density determination methods (such as from tissue's Linear attenuation coefficients and their CT numbers) compare to standard values. In addition, percentage error of the relative electron density calculated from the linear attenuation coefficient and the CT number were compared.
Results: The constructed anthropomorphic male RANDO Phantom consists of 175 layers with 1 cm thickness, 175 cm height and 72 kg weight. validating the constructed phantom by two methods demonstrate good agreement between tissue substitute materials in phantom structure in compare to standard values that suggested from ICRU44. percentage error difference in the relative electron density calculated from the linear attenuation coefficient and the CT number was in a good range between 0 -5.91. In the other hand there is no significant difference between reD obtained from these two methods and real tissue electron density (P-value < 0/05) so it can be concluded that both methods are reliable for phantom validation process.
Conclusion: Lower limbs can be a good bench mark for evaluation for patients with skin cancers so design of the whole body phantom with two lower limbs is very necessary. The another advantages of this study is use of high stability material that do not destroy over time. Finally, the constructed phantom in this study is recommended for TBI and TSET.