Gallium-68-Labelled Indocyanine Green as a Potential Liver Reserve Imaging Agent

This work evaluated the potential of ⁶⁸Ga-labelledNOTA-ICG (1,4,7-triazacyclononane-1,4,7-triacetic acid indocyanine green) for liver reserve imaging.

To determine the optimal conditions for generating ⁶⁸Ga-NOTA-ICG, various reaction parameters were implemented. Quality control analysis was performed using different chromatography techniques. The in vitro and in vivo stability was also measured at specific time points. The radioactivity ratio between n-octanol and water was determined to evaluate the water solubility of ⁶⁸Ga-NOTA-ICG. The plasma-protein binding rate of the labelled compound was determined by the methanol method. The biodistribution and imaging findings were evaluated in normal animals at different time points after injection. A preliminary imaging evaluation was performed using an animal model of hepatic ischaemia-reperfusion injury, which was confirmed by pathology.

⁶⁸Ga-NOTA-ICG was prepared with very high radiochemical purity (>98%) by reacting at 90°C for 10 min at pH = 3.5∼4.0, with excellent stability in vivo and in vitro (>95% 3 h postpreparation). The in vitro plasma-protein binding rate of ⁶⁸Ga-NOTA-ICG was 13.01 ± 0.7%, and it showed strong water solubility (log P=-2.01 ± 0.04). We found that in addition to excretion through the biliary tract and intestines, ⁶⁸Ga-NOTA-ICG can be excreted through the urinary tract. The image quality of ⁶⁸Ga-NOTA-ICG was very high; imaging agent retained in the area of liver injury could clearly be observed.

This is the first report on a ⁶⁸Ga-labelled NOTA-ICG fragment for liver reserve function studies. This complex has promise as a candidate agent for liver reserve imaging.