Monitoring the accumulation and photobleaching of protoporphyrin IX and photo-protoporphyrin during photodynamic therapy under dual-wavelength fluorescence excitation

Studying kinetics of PpIX accumulation in tissue helps identify optimal time intervals for PDT based on PS and photoproduct concentrations, optimizing irradiation. Ppp photoproducts exhibit photodynamic activity, allowing Ppp consideration as an additional photosensitizer that enhances therapeutic effect. Study involved optical phantoms simulating skin properties with accumulated PpIX, two patients with skin neoplasms. PDT used 20% aqueous 5-ALA solution prepared before administration. Spectral fluorescence diagnostics employed lasers (405 nm, 632.8 nm), spectrometer, and Y-shaped optical fiber. PDT used lasers (635 nm, 660 nm). Photoproducts formation was analyzed using 405 nm and 660 nm lasers. PDT with 635 nm irradiation led to photoporphyrin formation in studied areas. Fluorescence intensity of photoporphyrins declined slower than PpIX. Under 660 nm excitation, photoproduct fluorescence decreased significantly. Monitoring photoproduct formation is crucial for improving 5-ALA PDT efficiency. Differences in PpIX accumulation dynamics between superficial and deeper tissue layers enhance diagnostics accuracy and PDT precision.