High optical-throughput spectroscopic singlet oxygen and photosensitizer luminescence dosimeter for monitoring of photodynamic therapy |
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Authors: | Youbo Zhao Tobias Moritz Michael F. Hinds Jason R. Gunn Jennifer R. Shell Brian W. Pogue Steven J. Davis |
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Affiliation: | 1. Physical Sciences Inc, 20 New England Business Center Dr., Andover, MA, 01810 USA;2. Thayer School of Engineering, Dartmouth College, 14 Engineering Dr., Hanover, NH, 03755 USA |
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Abstract: | We report a high light-throughput spectroscopic dosimeter system that is able to noninvasively measure luminescence signals of singlet oxygen (1O2) produced during photodynamic therapy (PDT) using a CW (continuous wave) light source. The system is based on a compact, fiber-coupled, high collection efficiency spectrometer (>50% transmittance) designed to maximize optical throughput but with sufficient spectral resolution (~7 nm). This is adequate to detect 1O2 phosphorescence in the presence of strong luminescence background in vivo. This system provides simultaneous acquisition of multiple spectral data points, allowing for more accurate determination of luminescence baseline via spectral fitting and thus the extraction of 1O2 phosphorescence signal based solely on spectroscopic decomposition, without the need for time-gating. Simultaneous collection of photons at different wavelengths improves the quantum efficiency of the system when compared to sequential spectral measurements such as filter-wheel or tunable-filter based systems. A prototype system was tested during in vivo PDT tumor regression experiments using benzoporphyrin derivative (BPD) photosensitizer. It was found that the treatment efficacy (tumor growth inhibition rate) correlated more strongly with 1O2 phosphorescence than with PS fluorescence. These results indicate that this high photon-collection efficiency spectrometer instrument may offer a viable option for real-time 1O2 dosimetry during PDT treatment using CW light. |
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Keywords: | near-infrared spectroscopy photodynamic therapy photosensitizer luminescence singlet oxygen dosimeter |
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