[en] Cerenkov luminescence imaging (CLI) is a new method of optical molecular imaging, which has been successfully applied in early clinical trials. However, weak signal intensity and limited ability in tissue penetration have impeded its clinical application. Cerenkov radiation energy transfer imaging and radiation excitation fluorescence imaging were adopted to solve these problems by enabling transformation of some of the blue-weighted Cerenkov luminescence (CL) spectra to red-shifted emissions, or by exciting rare earth particles to emit visible and near infrared light. This article reviews the development of Cerenkov signal enhancement by fluorescence excitation effect. (authors)

[en] 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 eMPIoyed 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. (authors)