Internal Dosimetry of Human Brain for 99m tc and 131 I Using Nuclear Imaging in Bangladesh

Internal dosimetry deals with the measurement of the radiation dose absorbed internally by an organ after the application of isotopes for diagnosis and treatment. In the present study radiation absorbed dose has been calculated for 99m Tc-pertechnetate, 99m Tc-DTPA, 99m Tc–hepatate and 131 I (NaI) which are used frequently for functioning test of disordered organs and therapeutic treatment of thyroid in Bangladesh. In these cases a small amount of isotopes are accumulated in other soft tissues like brain, gonads etc. Brain tissues are soft and cannot be regenerated if it is damaged. So, to ensure the safety of brain, the internal radiation absorbed dose has been calculated from direct measurement by using planer image of gamma cameras. International Commission for Radiological Protection (ICRP) and National Commission for Radiation Protection (NCRP) have laid emphasis on direct measurement because it provides more accurate result than that of other methods which are based on few mathematical assumption, bio-kinetic modeling and extrapolation of animal data to human etc. Finally these results have been compared with the data of ICRP publication 71.