Internal dosimetry of technetium-99m and iodine-131 radio-pharmaceuticals by using planner and spect imaging

Abstract

Internal dosimetry is the branch ofMcdical Physics that deals with the measurement of the dose absorbed internally by an organ after the apphcation of isotopes for diagnosis and treatment. In thIS study internal radiation absorbed dose has been calculated for 9''''Te-pertcehnetate, 99"'Tc_DTPA, """'Te-hepatate and Llil which are used frequently for functioning test of disordered organs and therapeutic treatment of thyroid, in these cascs a small amount of Isotopes arc accumulated in other soft tissues like brain, Brain tissues are very soft and can not be regenerated if it is damaged, So, in order to ensure the safety of brain, the internal radiation absorbed dose has been calculated. Tn the present study, absorbed dose has been calculated from direct measurement International Commission for Radiological Protection ([CRP) and National Commission for Radiation Protection (NCRP) have put emphasis on direct measurcment because it provides more aCClirate result than that of olher methods which are based on few mathematical assumplion, biokinellc modelmg and extrapolation of animal data to human etc, Accumulations of isotopes in larget organ have been measured by using planer image of Gamma Cameras (SIEMENS E-CAM) and a Computer Based Scintillation System after a certain period from the time of exposure. This target organ is considered as the source with respect to other organs, To measure the amount of exposure for brain, data obtained with the help of calibraled data These calibrated data are obtained using water phantom with special set lip of equipments The system is calibrated usmg a radiation survey meter (Atom Lab 930), Absorbed dose in brain for each isotope has been calculated by applying limeactivity curves analysis, Finally these results have been compared with (he data oflCRP doc71