Application of fluorescein sodium on Cerenkov radiation energy transfer

Abstract

Objective To explore and evaluate the method and feasibility of applying the contrast agent fluorescein sodium to enhance the efficiency of Cerenkov radiation energy transfer (CRET). Methods Fluorescein sodium was employed as the energy transfer receptor of 18F-FDG Cerenkov radiation (CR) to achieve stronger signal. 18F-FDG was mixed with fluorescein sodium of different concentrations: 0.05, 0.10, 0.20, 1.00, 2.00, 4.00, 8.00 mmol/L. Optical signal strength was quantified by ROI analysis. The influence of fluorescein sodium concentration on CRET efficiency and the optimal concentration that could achieve most optical signal augmentation were studied. The optimal concentration of fluorescein sodium was mixed with 1.85-11.10 MBq 18F-FDG for CLI. Linear regression was performed to investigate the range of 18F-FDG dose with most optical signal augmentation and the influence of 18F-FDG dose on CRET efficiency. A tumor-bearing nude mouse was imaged after intravenous injection of 18F-FDG and then imaged again after injection of fluorescein sodium post 18F-FDG injection. These two sets of images were compared to evaluate the CRET efficiency in vivo. Results In vitro study showed that 1.00 mmol/L fluorescein sodium was the optimal concentration for 18F-FDG dose ranging from 1.85 MBq to 11.10 MBq. The signal from 18F-FDG mixed with fluorescein sodium was 3.7 times stronger than that from 18F-FDG alone. Experiment in vivo suggested that 18F-FDG mixed with fluorescein sodium could effectively enhance the signal strength by CRET. Conclusion 18F-FDG mixed with fluorescein sodium may improve the efficiency of CRET, therefore, can enhance the signal strength, reduce the exposure time and achieve better signal to noise ratio. Key words: Cerenkov luminescene imaging; Energy transfer; Fluorescein