Possibility for a full optical determination of photodynamic therapy outcome

Abstract

The microfluidic system for studies of carcinoma and normal cells interactions after photodynamic therapy (PDT) procedures Biomicrofluidics 5, 041101 (2011) Drug injection into fat tissue with a laser based microjet injector J. Appl. Phys. 109, 093105 (2011) A near infrared instrument to monitor relative hemoglobin concentrations of human bone tissue in vitro and in vivo Rev. Sci. Instrum. 81, 043111 (2010) Mechanism of oxidative stress generation in cells by localized near-infrared femtosecond laser excitation Appl. Phys. Lett. 95, 233702 (2009) Probing nanoantenna-directed photothermal destruction of tumors using noninvasive laser irradiation Appl. Phys. Lett. 95, 233701 (2009) Additional information on J. Appl. Phys. The efficacy of photodynamic therapy ͑PDT͒ depends on a variety of parameters: concentration of the photosensitizer at the time of treatment, light wavelength, fluence, fluence rate, availability of oxygen within the illuminated volume, and light distribution in the tissue. Dosimetry in PDT requires the congregation of adequate amounts of light, drug, and tissue oxygen. The adequate dosimetry should be able to predict the extension of the tissue damage. Photosensitizer photobleaching rate depends on the availability of molecular oxygen in the tissue. Based on photosensitizers photobleaching models, high photobleaching has to be associated with high production of singlet oxygen and therefore with higher photodynamic action, resulting in a greater depth of necrosis. The purpose of this work is to show a possible correlation between depth of necrosis and the in vivo photosensitizer ͑in this case, Photogem®͒ photodegradation during PDT. Such correlation allows possibilities for the development of a real time evaluation of the photodynamic action during PDT application. Experiments were performed in a range of fluence ͑0 -450 J / cm 2 ͒ at a constant fluence rate of 250 mW/ cm 2 and applying different illumination times ͑0-1800 s͒ to achieve the desired fluence. A quantity was defined ͑ ͒ as the product of fluorescence ratio ͑related to the photosensitizer degradation at the surface͒ and the observed depth of necrosis. The correlation between depth of necrosis and surface fluorescence signal is expressed in and could allow, in principle, a noninvasive monitoring of PDT effects during treatment. High degree of correlation is observed and a simple mathematical model to justify the results is presented.

Optimization of Photodynamic Therapy Using Negative Pressure

“…[23][24][25] The fluorescence spectroscopic technique has also been used as a diagnostic tool evaluating the spectral modifications on tissue, and can be applied in the diagnosis of tumor tissues and in liver transplantation, as well as in the evaluation of tissue modifications after death. 15,26,27 In agreement with our results, the maximum amount of PPIX production, evaluated by fluorescence spectroscopic and widefield fluorescence imaging analyses, is faster and greater in the deeper layers (30%) than at the surface (20%) 6 h after the initiation of the study. Six h after the application of 20% 5-ALA cream, PPIX formation in deeper layers decreased, but remained constant in the surface layer of the NP-G, and increased for 24 h in the CG, remaining constant after that.…”

“…12 For fluorescence spectrum analysis, we collected the fluorescence spectrum in contact with the tissue at five points in the 9 cm 2 circular area. At each point, 20 fluorescence and autofluorescence measurements were performed.…”

Determination of the threshold dose distribution in photodynamic action from in vitro experiments

“…Based on it, there are currently three strategies under investigation. Explicit Dosimetry is the measurement of the various factors such as photosensitizer degradation, oxygen concentration and light distribution to calculate PDT dose while implicit dosimetry relies on the an indirect quantity, the fluorescence or photobleaching of the photosensitizer, for example [45], [46]. Direct dosimetry, in the other hand, refers to the detection of singlet oxygen emission at 1270 nm [47].…”

Microneedles rollers as a potential device to increase ALA diffusion and PpIX production: evaluations by wide-field fluorescence imaging and fluorescence spectroscopy

“…The excitation laser was coupled with a Y-type probe that delivers the excitation light and collects the emitted fluorescence from the surface through six fibers distributed around the central excitation laser as previously described first [9]. The system is carried by a probe in Y, and in the region of excitation filters are used to remove the backscattered light.…”