Preliminary Dosimetry Study of 67Ga-AATS for Human Based on Biodistribution Data in Rats

Abstract

Introduction <br/>Gallium-67 (⁶⁷Ga) has been used as a radionuclide for imaging a variety of solid tumors since 1969. Since then use of various gallium-based radiotracers has been reported. Recently, ⁶⁷Ga-labeled acetylacetate bis(thiosemicarbazones) (⁶⁷Ga-AATS) complex with significant tumor accumulation and fast blood clearance has been employed. <br/>Materials and Methods <br/>In this study, the absorbed dose of ⁶⁷Ga-AATS in each human organ was evaluated and compared with ⁶⁷Ga-citrate as the most commonly used form of ⁶⁷Ga in nuclear medicine. ⁶⁷Ga was produced via ⁶⁸Zn(p,2n)⁶⁷Ga reaction at 30 MeV cyclotron. Moreover, ⁶⁷Ga-AATS was produced by adding 50 µl of AATS to absolute ethanol (1 mg/ml) in a gallium-containing vial at 80-90 ^°C. The absorbed dose of each human organ was calculated, using RADAR method, based on biodistribution data in Wistar rats. <br/>Results <br/>According to the results,⁶⁷Ga-AATS was produced with radionuclidic and radiochemical purity higher than 99% and 93%, respectively. The highest absorbed dose was reported in the bone surface (0.401 mGy/MBq), whereas the whole-body absorbed dose was 0.092 mGy/MBq. <br/>Conclusion <br/>The absorbed dose of each human organ was comparable with the absorbed dose received by each organ after ⁶⁷Ga-citrate injection. Considering this interesting finding and the significant tumor uptake, it seems that ⁶⁷Ga-AATS can be used as an appropriate SPECT tracer.