Two-Wavelength Fluorescence Monitoring and Planning of Photodynamic Therapy

Abstract

The aim of the study is to develop approaches for fluorescence monitoring and planning of photodynamic therapy employing chlorine series photosensitizers. Materials and Methods. The study included numerical simulations and experiments with optical agar phantoms of biotissue and human skin in vivo. Fluorescence imaging was used as a method of optical monitoring. Chlorine series photosensitizer Photoditazin (Veta Grand, Russia) was employed. Numerical simulation of light propagation was performed with Monte-Carlo technique for a multilayer skin model. Results. It was demonstrated that in the case of two-wavelength fluorescence monitoring of photosensitizer penetration into the tissue the ratio of fluorescence signals excited at wavelengths of 405 and 660 nm can be used as a characteristic of photosensitizer penetration depth in biological tissue. The results of numerical simulations are in good agreement with the results of model experiments on agar phantoms and pilot in vivo experiment. Radiant exposure and absorbed light dose maps at the wavelengths of 405 and 660 nm were calculated employing Monte-Carlo technique; the dependencies of the characteristic dose values on the optical properties of the medium were analyzed. Conclusion. Two-wave fluorescence imaging technique allows for non-invasive estimation of chlorine series photosensitizer penetration depth into the biotissue after topical application, while numerical simulation by Monte-Carlo method allows for more accurate choice of the light exposure dose for photodynamic therapy depending on optical properties of the tissue and the radiation wavelength.

Photodynamic therapy with chlorin-based photosensitizer at 405 nm: numerical, morphological, and clinical study

“…Development of the optimal protocols of PDT procedure is the key element in the success of PDT treatment. Presence of absorption peaks at 402 and 662 nm in chlorin-based PS 42 provides additional opportunities for the choice of irradiation regimens. Traditionally, the wavelengths around 660 nm are employed for irradiation due to deeper penetration in tissues; however, for superficial impact wavelengths around 405 nm could be beneficial, especially in case of antibacterial or antiaging PDT.…”

“…The details of this approach to PDT monitoring are given in paper. 42 Visual inspection revealed no changes in the skin of the rabbit ear after the PDT procedure in the course of 8-day monitoring.…”

“…In this study, we employed previously developed Monte Carlo code 41,42 to simulate dose absorption maps for irradiation of skin and mucous tissue at the wavelengths of 405 and 660 nm and compare typical impact depths. Monte Carlo technique is based on the simulation of a large number of random photon walks in a given turbid medium with the specified optical properties and subsequent statistical analysis of the collected data.…”

Combined Application of Dual-Wavelength Fluorescence Monitoring and Contactless Thermometry during Photodynamic Therapy of Basal Cell Skin Cancer

“…Monitoring of the PDT procedure for BCSC treatment was performed using dual-wavelength fluorescence imaging system developed at the Federal Research Center Institute of Applied Physics of the Russian Academy of Sciences (Nizhny Novgorod, Russia) [ 8 , 9 ]. Fluorescence monitoring is based on the registering photobleaching of the photosensitizer accumulated in the tumor manifested by the reduction of the fluorescence response signal level during the procedure.…”

“…Optical properties of the skin at 402 and 662 nm wavelengths differ significantly: skin absorption depending mainly on water and hemoglobin is much lower at 662 nm as compared to 402 nm [ 7 ]. In this connection, dual-wavelength fluorescence excitation gives additional information, since at 405 nm wavelength it provides a signal from the superficial tissue layers whereas at 660 nm the probing depth appears to be essentially greater [ 8 , 9 ].…”