Estimation of human effective absorbed dose of 67Ga-cDTPA-gonadorelin based on biodistribution rat data.
OBJECTIVE
In this investigation, we estimated the effective absorbed dose of radiation into human organs, after an intravenous administration of gallium-67 (67Ga)-labeled gonadorelin, one of the gonadotropin-releasing hormone (GnRH) agonists, using biodistribution data from injected normal rats.


METHODS
Five rats were killed at exact time intervals (0.25, 0.5, 1, 2, 4, 24, and 48 h post injections) and the percentage of injected dose per gram of each organ was measured by direct counting from rat data. The Medical Internal Radiation Dose formulation was applied to extrapolate from rat to human and to project the absorbed radiation dose for various organs in humans.


RESULTS
From rat data we estimated that a 185-MBq injection of 67Ga-cDTPA-GnRH into the humans might result in an estimated absorbed dose of 5.26 mGy in the whole body with the highest effective absorbed dose was in the lungs (2.73 mSv), and the organs that received the next highest doses were the bladder wall (1.59 mSv), liver (0.80 mSv), and bone marrow (0.52 mSv).


CONCLUSIONS
The biodistribution of 67Ga-cDTPA-GnRH in rats showed high breast uptake and low muscle and blood uptake. These results suggest that it should be possible to perform early imaging of the breast anomalies and GnRH receptors indicating potential malignant lesions.
Department of Biomedical Physics and Engineering, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. shanehsazzadeh@razi.tums.ac.ir
Saeed
S
Shanehsazzadeh
Afsaneh
A
Lahooti
Hamid Reza
HR
Sadeghi
Amir Reza
AR
Jalilian
D000595:Amino Acid Sequence; D000818:Animals; D005260:Female; D005710:Gallium Radioisotopes / Q000737:chemistry; D007987:Gonadotropin-Releasing Hormone / Q000737:chemistry* / Q000493:pharmacokinetics*; D006801:Humans; D004369:Pentetic Acid / Q000737:chemistry*; D011829:Radiation Dosage; D011874:Radiometry; D051381:Rats
D005710:Gallium Radioisotopes; D007987:Gonadotropin-Releasing Hormone; D004369:Pentetic Acid