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
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