Developing the Adult Male ICRP Phantom and Evaluation the Absorbed Dose Received By Critical Organs in Head and Neck Region during the Radiotherapy of Eye Cancer

Introduction Accurate estimation of the absorbed dose in radiosensitive organs, located away from the target volume during radiotherapy, is one of the main reasons for the development of reference phantoms. The International Commission on Radiological Protection (ICRP) reference phantoms can provide a more realistic view of the human anatomy in comparison with the previously used mathematical phantoms. However, the ICRP reference phantoms seem to have certain limitations, resulting in the inaccurate eye simulation due to the absence of super-high-resolution CT scan images. Materials and Methods In this study, we developed a modified version of the ICRP reference phantom by inserting a realistic eye phantom into the voxelized phantom. In addition, by using the developed model, the absorbed dose received by sensitive organs (e.g., thyroid, brain, and different parts of the eye) during radiotherapy of a common ocular surface tumor was determined. The results were compared with those obtained by the modified phantom developed by the University of Florida-Oak Ridge National Laboratory (UF-ORNL). Results Based on the results, the relative difference between the equivalent doses calculated by the developed phantom and UF-ORNL phantom was nearly 75-95% and 3% for thyroid and eye substructures, respectively. Conclusion Despite of many advantageous of voxel phantoms, they have considerable limitation in providing accurate model of the eye. In the present study, a detailed stylized model was developed and incorporated into the Adult Male (AM) reference and UF-ORNL phantoms. These phantoms were then used for the dosimetric calculations during eyelid cancer therapy.