Mouse tissue attenuation is stronger for FLI than BLI. (a) B16-luc and B16-RFP tumors have similar specific signal ex vivo. Excised tumors from a total of 5 mice ( for BLI and for FLI) were subjected to imaging. Data for individual tumors ( for BLI and for FLI) and the median are shown. NS, no significant difference (, Mann-Whitney test). (b) Optical signal is strongly decreased in vivo for FLI on shaved mice. Tumors were scanned in vivo before excision. Data for individual tumors ( for BLI and for FLI) and the median are shown. The tumors are the same as those described in (a). *, significant difference (, Mann-Whitney test). (c) Mouse hair strongly decreases the optical signal for FLI. B16-luc and B16-RFP tumors were imaged in vivo before and after shaving. A representative mouse for each technique ( and mice analyzed for BLI and FLI, resp.) is shown.