Radiation Hazards Investigation of Photon Scattering by Elekta 6 MeV Linac during Liver Cancer Treatment

Medical accelerators such as Elekta linac are used to treat cancer and imaging. Depending on cancer type, they regulate certain field size. Because of photon scattering from accelerator components, for every field size to treat cancer, air and patient’s body, there is the radiation risk for other organs. In this research, the scattering factor for different fields of Elekta linac is first calculated using the phase space specifications in GEANT4 and MCNPX codes. Due to the scattering of photons, the calculated dose in other body organs in the treatment of liver cancer was calculated using the MIRD phantom and the accelerator phase space. For 15 Gy dose in liver cancer treatment, the other organs also receive a significant dose due to their distance from the liver. Even brain tissue that is far from the liver and is out of treatment plan receives about 0.47 Gy dose. One of the major problems of radiotherapy is the inability to accurately focus on the radiation field size of the cancerous tissue. Even by precisely adjusting the field size to the tumor size, there is a risk of radiation to the tissues around the tumor due to the scattering of photons from the air, accelerator components, and patients’ body parts. Until now, it has been assumed that small volumes of healthy tissue around the tumor are at radiation risk in radiotherapy procedures. However, the results of this study showed that the radiation risk from radiotherapy procedures is much higher in the tissues near the tumor.