RESUMO
Quantitative fluorescence spectroscopy requires corresponding reflectance measurements to correct for tissue absorption and scattering. However, it is unclear whether fluorescence adds value beyond the diffuse reflectance measurements necessary for correction. The goal of this study was to compare the accuracy of fluorescence and diffuse reflectance spectroscopy in recovering the concentration of a high-extinction fluorophore, methylene blue (MB), using a compact fiber-optic probe. Fluorescence and diffuse reflectance measurements of tissue simulating phantoms were made using a fiber-optic probe with source-detector separations of 288-1300 µm. Average error in recovered fluorophore concentration was 20.4% for fluorescence and 15.0% for reflectance, though this difference was not significant (p=0.77). Both methods returned concentrations that were similar to known MB concentrations (p≥0.79 in both cases). Fluorescence quantification of the concentration of a high extinction fluorophore did not significantly improve accuracy relative to diffuse reflectance. Investigators should consider whether fluorescence measurements are necessary for a given application.
RESUMO
We describe a compact fiber-optic probe (2â mm outside diameter) that utilizes spatially-resolved diffuse reflectance for tissue optical property recovery. Validation was performed in phantoms containing Intralipid 20% as scatterer, and methylene blue (MB), MnTPPS, and/or India ink as absorbers. Over a range of conditions, the reduced scattering coefficient was recovered with a root mean square error (RMSE) of 0.86-2.7â cm-1 (average error = 3.8%). MB concentration was recovered with RMSE = 0.26-0.52â µM (average error = 15.0%), which did not vary with inclusion of MnTPPS (p=0.65). This system will be utilized to determine optical properties in human abscesses, in order to generate treatment plans for photodynamic therapy.
