Singlet oxygen (1O2) is widely considered as the major cytotoxic species generated during Type-II photochemical reaction of photodynamic therapy (PDT), and its production is crucial for the treatment outcome of PDT. However, it is still a challenging task for direct detection of 1O2 by using an optical system as its extremely weak luminescence at 1270 nm. In previous study, a high-sensitivity optical fiber detection system has been developed to measure the time-resolved 1O2 luminescence spectra. In this study, an optical phantom of skin tissue has been built to simulate the skin optical properties for research in photodynamic therapy (PDT). The phantom consists of an absorber (ink) and a scatterer (Intralipid) and phosphate buffer saline (PBS). Rose Bengal (RB) was utilized as the model photosensitizer to generate 1O2. The time-resolved 1O2 luminescence spectroscopy were measured by using a 1O2 luminescence detection system with a fiber prober in tissue phantom. Furthermore, the effect of absorption coefficient (μa) and scattering coefficient (μs) on the photosensitizer triple state lifetime (τT) and 1O2 luminescence lifetime (τD) was investigated as well. The results indicated that the integrated intensity of 1O2 luminescence decrease with the increase of μa and μs. μa has no significant effect on τT and τD. τT increase with the increase of μs, and it finally stabilized around 1.6 μs. Meanwhile, τD decrease firstly and then increase slowly, and it finally stabilized around 14 μs. This result indicates that this system for 1O2 luminescence have a potential for clinical applications in PDT dosimetry.
Singlet oxygen (1O2) is the primary cytotoxic production in type-II photodynamic therapy (PDT). The correlation between 1O2 generation and PDT efficacy during treatment has received considerable attention. The direct detection of 1O2 luminescence is the gold standard for 1O2 identification. However, the intensity of 1O2 luminescence could be influenced by tissue optical properties, location and morphology of lesion, especially for vascular targeting PDT. In this study, the impacts of vascular diameter and depth on 1O2 luminescence imaging have been investigated in tissue simulating phantom. A near-IR sensitive InGaAs camera with adaptive optics and CW laser 532 nm were used for fast imaging of 1O2 luminescence. Rose Bengal (RB) was used as photosensitizer to generate 1O2 during photosensitization. Intralipid was diluted with different concentrations in order to establish the scattering properties of tissues. The capillary tubes, containing solution of RB, with varied diameters from 0.1 to 0.9 mm were used to simulate the vascular with the depth varied from 0 to 5 mm in phantom. The preliminary results indicate that the profile range ratio of 1O2 luminescence images are negatively correlated to the diameter of capillary tube, and the attenuation of intensity of 1O2 luminescence is non-linear with the increase of depth.