Figure 4: (a) The spectrum of two possible light sources for fluorescence guided surgery. The solid line illustrates the spectrum of a filtered Xenon lamp as used in Tran Cao et al. [1]. The dash line illustrates a typical blue LED spectrum. The color blocks mark the spectral range of red, green, and blue channels on common RGB CCDs. (b) Overlapping emission and excitation spectra of GFP/Alexa-488 and RFP/Alexa-555 fluorescent proteins and fluorophores. Blue and salmon color peaks represent the excitation and emission spectra of GFP/Alexa 488, respectively. Pink and Red peaks represent excitation and emission spectra of RFP/Alexa 555, respectively. This graphic demonstrates the utility of the overlapping spectra of these fluorophores in the spectral range of GFP in detecting tumor while maintaining adequate visualization of surrounding structures for spatial orientation and surgical navigation. Filtering an LED light source through a 495 glass filter creates the bandwidth by which tumors of different fluorescent colors are visualized simultaneously [3].