Fig. 1. Schematic of action principle of PDT

Fig. 2. Procedure for quantifying photosensitizer concentrations

Fig. 3. Factors affecting fluorescence intensity measurement of photosensitizers

Fig. 4. Instrumental factors affecting measurement of fluorescence intensity of photosensitizers^［23］

Fig. 5. Intrinsic factors affecting measurement of fluorescence intensity of photosensitizers. (a) Tissue optical properties; (b) endogenous fluorescence

Fig. 6. Calibration algorithms for fluorescence spectra

Fig. 7. Schematics of quantitative detection techniques of photosensitizer. (a) Schematic of contact spectroscopic probe; (b) schematic of non-contact wide-field imaging system

Fig. 8. Schematics of contact spectroscopic probes for quantitative fluorescence detection. (a) Novel contact probe-based fluorescence dosimeter^[41]; (b) in vivo photodynamic dosimeter probe using multi-excitation multi-emission system^[57]; (c) in vivo fluorescence quantitative detection probe based on multi-spectrum^[43]

Fig. 9. Schematics of non-contact wide-field imaging systems for quantitative detection of fluorescence intensity. (a) Quantitative spatial frequency domain fluorescence imaging^[32]; (b) snapshot quantitative fluorescence imaging system based on spatial frequency domain fluorescence imaging^[53]; (c) wide-field spectral-resolved fluorescence imaging system^[62]; (d) multimodal quantitative fluorescence imaging system^[3]