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.
In this work we studied the efficiency of spatially modulated illumination in optical diffuse reflectometry (ODR) and analyzed various probing patterns. The optimal illumination pattern was determined from the series of Monte Carlo numerical experiments on structured illumination and comparison of the parameters of fluence distribution within tissue. We considered the following illumination profiles: sinusoidal patterns with different spatial frequencies k (1 - 2.5 mm-1); piecewise constant patterns with the fixed duty cycle w = 2 and various strip width (0.2 – 1 mm); piecewise constant patterns with the fixed strip width (0.1 mm) and various duty cycle (3 – 11). Assuming the same total incident intensity for all patterns, we observed the growth in intensity at depth with decreasing value of spatial frequency for sinusoidal pattern, the similar tendency of intensity distribution was for piecewise constant patterns with the fixed strip width (or duty cycle) and duty cycle increase (or increase of a strip width, respectively). The intensity distributions within the sample are almost identical for sinusoidal and piecewise constant patterns with matching peaks and lows. However, probing by piecewise constant profile of illumination provide more local information about sample’s properties. A prototype of an ODR system for probing with the structured illumination was designed. The system consists of PC-controlled optical projection system, polarization filters and a CCD camera. The approbation of the system was carried out on the optical phantoms with optical properties close to those of biological tissues and on skin of human volunteers.