1 May 2009 In vivo quantification of chromophore concentration using fluorescence differential path length spectroscopy
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J. of Biomedical Optics, 14(3), 034022 (2009). doi:10.1117/1.3149862
We present an optical method based on fluorescence spectroscopy for measuring chromophore concentrations in vivo. Fluorescence differential path length spectroscopy (FPDS) determines chromophore concentration based on the fluorescence intensity corrected for absorption. The concentration of the photosensitizer m-THPC (Foscan®) was studied in vivo in normal rat liver, which is highly vascularized and therefore highly absorbing. Concentration estimates of m-THPC measured by FDPS on the liver are compared with chemical extraction. Twenty-five rats were injected with 0.3 mg/kg m-THPC. In vivo optical concentration measurements were performed on tissue 3, 24, 48, and 96 h after m-THPC administration to yield a 10-fold variation in tissue concentration. After the optical measurements, the liver was harvested for chemical extraction. FDPS showed good correlation with chemical extraction. FDPS also showed a correlation between m-THPC fluorescence and blood volume fraction at the two shortest drug-light intervals. This suggests different compartmental localization of m-THPC for different drug-light intervals that can be resolved using fluorescence spectroscopy. Differences in measured m-THPC concentration between FDPS and chemical extraction are related to the interrogation volume of each technique; ~0.2 mm3 and ~102 mm3, respectively. This indicates intra-animal variation in m-THPC distribution in the liver on the scale of the FDPS sampling volume.
Bastiaan Kruijt, Slávka Kascáková, Henriëtte S. de Bruijn, Angélique van der Ploeg-van den Heuvel, Henricus J. C. M. Sterenborg, Dominic J. Robinson, Arjen Amelink, "In vivo quantification of chromophore concentration using fluorescence differential path length spectroscopy," Journal of Biomedical Optics 14(3), 034022 (1 May 2009). https://doi.org/10.1117/1.3149862

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