Preliminary Human Radiation Dose Estimates of PET Renal Agents, Para-¹⁸F-Fluorohippuric Acid and Ortho-¹²⁴I-Iodohippuric Acid from Rat Biodistribution Data

Background: Para-¹⁸F-fluorohippuric acid (¹⁸F-PFH) and ortho-¹²⁴I-iodohippuric acid (¹²⁴IOIH) were recently identified as potential radiotracers suitable for conducting renography using positron emission tomography (PET). The aim of this work was to estimate preliminary human-equivalent internal radiation dose of ¹⁸F-PFH and ¹²⁴I-OIH using the biodistribution data reported in healthy rats. The results were compared with the absorbed dose data of technetium-99m-mercaptoacetyltriglycine (^99mTc- MAG3) as documented in the International Commission on Radiological Protection (ICRP) publication 80. Methods: The medical internal radiation dose (MIRD) formula was applied to extrapolate data from rats to human and to project the absorbed radiation dose for various organs in humans. S factor was calculated by Monte-Carlo N-particle (MCNP) simulation. Results: Our dose prediction shows that an injection of ¹⁸F-PFH or ¹²⁴I-OIH in humans would result in an estimated effective absorbed dose of 0.09 or 0.17 μSv/MBq respectively for whole body, which is about 135 or 73 times respectively lower than that obtained with an injection of ^99mTc-MAG3. All organs except kidneys would receive an estimated effective absorbed dose of <0.1 μSv/MBq for ¹⁸F-PFH or ¹²⁴I-OIH. Kidneys would receive a dose of 0.83 or 0.77 μSv/MBq respectively for ¹⁸F-PFH or ¹²⁴I-OIH. Conclusions: Our results indicate that ¹⁸F-PFH and ¹²⁴I-OIH would deliver much safer levels and lower radiation doses to the patients compared to ^99mTc-MAG3 and warrants a clinical trial to estimate the radiation doses more accurately.