Fig. 1.

Cerenkov luminescence imaging of the PET radioisotope ⁶⁸Ga in vitro. The positron-emitter ⁶⁸Ga was eluted from a generator (Eckert & Ziegler, Berlin, Germany) and its activity was measured using a calibrated dose calibrator (Capintec CRC 212). The manufacturer specified setting and calibration factor for ⁶⁸Ga was used for all measurements. Clear Eppendorf tubes containing various activity concentrations of ⁶⁸Ga were placed within the imaging chamber of a commercial bioluminescence imaging system (IVIS 100; Perkin Elmer, Waltham, MA). The IVIS system consists of a cryogenically-cooled charged couple device (CCD) camera, operating at −90 °C, and a temperature controlled, light-tight imaging chamber. Two sets of images were collected; a white-light image and a luminescence image that captured photon output due to Cerenkov luminescence. Photon flux was quantified by means of proprietary software (Living Image version 2.5) using custom regions of interest based on the outlines of the Eppendorf tube caps visible on the white-light image. A. CLI image of 89 kBq of ⁶⁸Ga. B. ROI analysis of photon flux demonstrated 1136,500 p/sec/cm²/sr. C. There is a positive linear relationship between the ⁶⁸Ga activity and measured luminescence (R² = 0.9996). The ⁶⁸Ga activities ranged from 19 to 1689 kBq and were imaged in triplicate using the IVIS 100 high resolution (4) setting, FOV15, f1, open filter for 30 s (Courtesy of CLW, MVK and MFT).