Cerenkov Luminescence Imaging (CLI) is an emerging technology for intraoperative margin assessment. Previous research only evaluated radionuclide 18-Fluorine (18F); however, for future applications in prostate cancer, 68-Gallium (68Ga) seems more suitable, given its higher positron energy. Theoretical calculations predict that 68Ga should offer a higher signal-to-noise ratio than 18F; this is the first experimental confirmation. The aim of this study is to investigate the technical performance of CLI by comparing 68Ga to 18F.

The linearity of the system, detection limit, spatial resolution, and uniformity were determined with the LightPath imaging system. All experiments were conducted with clinically relevant activity levels in vitro, using dedicated phantoms. For both radionuclides, a linear relationship between the activity concentration and detected light yield was observed (R2 = 0.99). 68Ga showed approximately 22 times more detectable Cerenkov signal compared to 18F. The detectable activity concentration after a 120 s exposure time and 2 × 2 binning of 18F was 23.7 kBq/mL and 1.2 kBq/mL for 68Ga. The spatial resolution was 1.31 mm for 18F and 1.40 mm for 68Ga. The coefficient of variance of the uniformity phantom was 0.07 for the central field of view.

68Ga was superior over 18F in terms of light yield and minimal detection limit. However, as could be expected, the resolution was 0.1 mm less for 68Ga. Given the clinical constraints of an acquisition time less than 120 s and a spatial resolution < 2 mm, CLI for intraoperative margin assessment using 68Ga could be feasible.

EJNMMI physics. 2019 Oct 24*** epublish ***

J Olde Heuvel, B J de Wit-van der Veen, K N Vyas, D S Tuch, M R Grootendorst, M P M Stokkel, C H Slump

Department of Nuclear Medicine, Netherlands Cancer Institute, Amsterdam, The Netherlands. ., Department of Nuclear Medicine, Netherlands Cancer Institute, Amsterdam, The Netherlands., Lightpoint Medical Ltd, Misbourne Works, Waterside, Chesham, HP5 1PE, UK., Robotics and Mechatronics , Technical Medical Centre, University of Twente, Enschede, The Netherlands.