Primary radiation dosimetry of a novel PET radiopharmaceutical Ga-NODAGA-glycine in comparison with Tc-DTPA in renal studies.

OBJECTIVE

In this study, we tried to estimate human absorbed dose of Ga-NODAGA-glycine as a new potential positron emission tomography (PET) renal agent based on the biodistribution data reported in healthy rats, and compare our estimation with the available absorbed dose data from technetium-99m-diethylenetriaminepentaacetic acid (Tc-DTPA).

SUBJECTS AND METHODS

The medical internal radiation dose (MIRD) formulation was applied to extrapolate from rats to human and to project the absorbed radiation dose for various organs in humans. S factor calculated by Monte-Carlo N-particle (MCNP) simulation and also this factor has been taken from the tables presented in MIRD pamphlet No.11. Hence, two radiation absorbed dose were calculated for organs.

RESULTS

Our dose prediction shows that an 185MBq injection of gallium-68-1,4,7-triazacyclononane-1-γ-glutamylglycine-4,7-diacetic acid (Ga-NODAGA-glycine) in humans might result in an estimated absorbed dose of 0.063mGy in the whole body when S factor calculated by MCNP simulation. The highest absorbed doses are observed in kidneys, lungs, spleen, liver, and red marrow with 3.510, 0.453, 0.335, 0.268, and 0.239mGy, respectively. In addition to, the estimated absorbed dose for total body after injection of 185MBq of Ga-NODAGA-glycine is 0.053mGy when S factor has been taken from MIRD pamphlet No.11. The highest absorbed doses are observed in kidneys, lungs, liver, spleen, and red marrow with 3.110, 0.438, 0.209, 0.203, and 0.203mGy, respectively. Comparison between human absorbed dose estimation for Ga-NODAGA-glycine and Tc-DTPA indicated that the absorbed dose of the most organs after injection of Tc-DTPA is higher than the amount after Ga-NODAGA-glycine.

CONCLUSION

The results showed that Ga-NODAGA-glycine delivers lower dose to the patients. Also due to its application in PET (which offers higher sensitivity and spatial resolution compared to planar or SPET), Ga-NODAGA-glycine would be a superior choice than Tc-DTPA for renography and impose less radiation doses to patients.