FIGURE 9.
Comparison of detection of tdTomato fluorescence and GFP fluorescence in mouse cadaver phantom with Xenogen IVIS 200 system. (A) Upper left image shows fluorescence from tubes packed with 100 × 106 cells expressing MDA-MB-231-tdTomato (red) or MDA-MB-231-GFP (green). Below these are false-color-overlay images (0.01-s exposure time) using either GFP filter set or DsRed set. White tubes in these images indicate that tdTomato did not fluoresce when GFP was being imaged and GFP did not fluoresce when tdTomato was being imaged. Mouse false-color-overlay images (regions of interest circled; 1-s exposure time) at center and right show that only tdTomato fluorescence could be detected from implanted tubes. (B) Panel showing similar results to those in A, only number of tdTomato cells used was 45 × 106 while number of GFP-expressing cells remained same. Implanted tubes are shown on left; red and green fluorescence was easily detected (0.01-s exposure times). (C) Unprocessed fluorescent images with 2.5-s exposure times show that autofluorescence from fur of SCID mouse depends on emission wavelength filter used. Tube implants were those shown in A (left image), B (center image), and tube containing 9.25 × 106 cells expressing tdTomato (right image). Regions of interest are circled in first 2 cases. Left and center images show intense fur autofluorescence that masks detection of implanted fluorescence signals. Right image indicates that use of 620-nm emission filter allowed lowest number of tdTomato cells implanted to be detected (fluorescent signal indicated by arrow) above fur autofluorescence. (D) Images illustrating excellent sensitivity of optical imaging. False color overlay at left, with region of interest circled, shows detection of fluorescence signal from 9.25 × 106 implanted tdTomato-expressing cells using 0.01-s exposure and 620-nm emission filter. Faint fluorescence from implant has been made visible by enhancing central image with PhotoShop (Adobe), as indicated by arrow in image at right.