Fig. 2.

(a) Fluorescence labeling with eight different tetracycline derivates using different fluorescence filter sets for green/red/infrared [SKY, Applied Spectral Imaging, Israel (no permission to publish filter details)], green (#09, Zeiss; excitation 450–490 nm, beam splitter/emission 515 nm) as well as a long-pass emission filter (#01 Zeiss; for details see Fig. 3). Note that doxycycline and rolitetracycline appear in different colours, but reveal a very similar emission spectra with the same wavelength peak (see Fig. 3). (b) Spectral image acquisition of the same bone area using a long-pass emission filter. Note that the tetracycline bands are more discernible. (c) By linear unmixing and false colour depiction, chlortetracycline (blue) can be distinguished and depicted separately from the other fluorochromes (red). 1: chlortetracycline; 2: methacycline; 3: tetracycline; 4: rolitetracycline; 5: minocycline; 6: oxycycline; 7: demeclocycline; 8: doxycycline.