Employment of chlorin-based photosensitizers (PSs) provides additional advantages to photodynamic therapy (PDT) due to absorption peak around 405 nm allowing for superficial impact and efficient antimicrobial therapy. We report on the morphological and clinical study of the efficiency of PDT at 405 nm employing chlorin-based PS. Numerical studies demonstrated difference in the distribution of absorbed dose at 405 nm in comparison with traditionally employed wavelength of 660 nm and difference in the in-depth absorbed dose distribution for skin and mucous tissues. Morphological study was performed at the inner surface of rabbit ear with histological examinations at different periods after PDT procedure. Animal study revealed tissue reaction to PDT consisting in edema manifested most in 3 days after the procedure and neoangiogenesis. OCT diagnostics was confirmed by histological examination. Clinical study included antimicrobial PDT of pharynx chronic inflammatory diseases. It revealed no side effects or complications of the PDT procedure. Pharyngoscopy indicated reduction of inflammatory manifestations, and, in particular cases, hypervascularization was observed. Morphological changes were also detected in the course of monitoring, which are in agreement with pharyngoscopy results. Microbiologic study after PDT revealed no pathogenic bacteria; however, in particular cases, saprophytic flora was detected.
Optical coherence tomography (OCT) is currently actively introduced into clinical practice. Besides diagnostics, it can be efficiently employed for treatment monitoring allowing for timely correction of the treatment procedure. In monitoring of photodynamic therapy (PDT) traditionally employed fluorescence imaging (FI) can benefit from complementary use of OCT. Additional diagnostic efficiency can be derived from numerical processing of optical diagnostics data providing more information compared to visual evaluation. In this paper we report on application of OCT together with numerical processing for clinical diagnostic in gynecology and otolaryngology, for monitoring of PDT in otolaryngology and on OCT and FI applications in clinical and aesthetic dermatology. Image numerical processing and quantification provides increase in diagnostic accuracy. Keywords: optical coherence tomography, fluorescence imaging, photod
For correct identification of fluorophores in fluorescence lifetime imaging invivo it is important to account for widening of fluorescent kinetics curve due to light scattering and absorption in turbid medium. This widening leads to the difference between real and measured lifetimes of a fluorescent agent. We studied this effect for media with different optical properties and lifetimes corresponding to those of real fluorophores applying Monte-Carlo simulation. We found that for the fluorophore depths up to 15 mm for reduced scattering coefficient varying from 0.15 to 4.8 mm-1 and absorption coefficient varying from 0.0025 to 0.08 mm-1 this difference is insignificant for long-lived fluorophores (typical fluorescent proteins), however, it should be taken into account for fluorophores with lifetimes of several hundred picoseconds. Results of numerical simulation are confirmed by the results of the model experiment.
Correct identification of different fluorophores in the fluorescence lifetime imaging in vivo requires accounting for distortion of the measured fluorescent kinetics curve due to light scattering and absorption in medium. This distortion induces the difference between real and measured lifetimes of a fluorophore. We obtained analytical expression based on diffuse approximation of radiation transfer equation that allows to refine estimating the lifetime of a fluorophore. It was shown that our approach can be applied both for analytic kinetics curves obtained by diffuse approximation, Monte Carlo simulated curves and results of model experiment. Analytical and Monte Carlo simulated curves were obtained for media with different optical properties and lifetimes corresponding to those of real fluorophores. Results of numerical simulation are confirmed by the results of the model experiment.