Radiation dosimetry for technetium-99m-MAG3, technetium-99m-DTPA, and iodine-131-OIH based on human biodistribution studies

Radiation dose estimates were calculated for the renal agents 99mTc-DTPA, 99mTc-MAG3, and 131I-OIH from biodistribution data gathered in groups of healthy human volunteers. Biokinetics were evaluated by Anger camera imaging, blood sampling, and urine collection and counting. Collected data were fit to four- or five-compartmental models using the CONversational Simulation, Analysis, and Modeling (CONSAM) software. Radiation dose estimates were performed using standard MIRD techniques. Average residence times in urinary bladder, kidney, and remainder of the body were used to predict radiation dose equivalents and effective dose equivalents for the three agents. Doses for DTPA and MAG3 were very similar and much lower on a per unit injected activity than OIH. The effective dose equivalents were 3.3 mSv/370 MBq for 99Tc-DTPA, 3.7 mSv/370 MBq for 99mTc-MAG3, and 0.99 mSv/11.1 MBq for 131I-OIH for bladder voiding every 4.8 hr; effective dose equivalents were 2.0 mSv/370 MBq for 99mTc-DTPA, 1.5 mSv/370 MBq for 99mTc-MAG3, and 0.28 mSv/11.1 MBq for 131I-OIH for bladder voiding at 30 min and then every 4.0 hr. Patients should void at the conclusion of the study, as early voiding can reduce the gonadal radiation dose by a factor of 2 to 3.