Sensitivity evaluation of endoscopic Cerenkov luminescence imaging system

Objectives An endoscopic Cerenkov luminescence imaging (ECLI) system was developed to detect Cerenkov luminescence emitted from a radionuclide probe deep inside the living body. This study was presented to evaluate the sensitivity of the developed system with in vitro and in vivo studies.

Methods The ECLI system consists of three parts, an electron multiplying charge coupled device (EMCCD) camera, a fiber endoscope and an optical adaptor. The fiber endoscope was used to transmit Cerenkov luminescent as well as white-light images; The EMCCD was used to collect the feeble Cerenkov luminescent and photographic images; and the optical adapter was adopted to organically integrate the fiber endoscope and the EMCCD.

Results Sensitivity of the ECLI system was evaluated with both in vitro and in vivo experiments. Firstly, the in vitro experiment was conducted using a 96-well plate with one of wells filled of 5μCi 68Ga. The ECLI system was used to collect the Cerenkov luminescent images. The images were sequentially acquired over 230 min, and exposure time of 5 min for each image, as shown in Figure 1A. Average intensity of region of interest was calculated for each image to plot a fitting curve, as shown in Figure 1B. Secondly, a nude mouse with a pseudotumor formed by 15μCi of 68Ga that was mixed into thirty μL Matrigel (BD Biosciences) was to mimic the in vivo study, and the same sequential images as those in the in vitro experiment were acquired. Similarly, a fitting curve was also plotted in the same way, as shown in Figure 1C.

Conclusions This study has investigated the sensitivity of the developed ECLI system using both in vitro and in vivo experiments, with the theoretical sensitivity being 1.53μCi and 2.82μCi respectively. We believed that this study will accelerate the translation of Cerenkov luminescence imaging technique into clinical applications.

Research Support This work was partly supported by the Program of the National Basic Research and Development Program of China (973) under Grant No. 2011CB707702, the National Natural Science Foundation of China under Grant Nos. 81090272, 81227901, 81101083, 81201137, the Open Research Project under Grant 20120101 from SKLMCCS, and the Fundamental Research Funds for the Central Universities.