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Special Section on Optical Diagnostic Imaging from Bench to Bedside Spectroscopy

Paired-wavelength spectral approach to measuring the relative concentrations of two localized chromophores in turbid media: an experimental study

[+] Author Affiliations
Ning Liu, Angelo Sassaroli, Sergio Fantini

Tufts University, Department of Biomedical Engineering, 4 Colby Street, Medford, Massachusetts 02155

J. Biomed. Opt. 12(5), 051602 (September 20, 2007). doi:10.1117/1.2779349
History: Received February 27, 2007; Revised April 13, 2007; Accepted May 17, 2007; Published September 20, 2007
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We present an experimental test of a new spectral approach that is aimed at quantifying the relative concentrations of two chromophores that are contained in a defect embedded in a turbid medium. The basic steps of our spectral approach are (a) perform a linear tandem scan of the source and detector across the defect; (b) measure the spectral dependence of the maximum change induced by the defect in the scanned intensity; (c) identify a set of appropriate pairs of wavelengths (λ1, λ2) at which such maximum intensity changes are the same; and (d) measure the reduced scattering coefficient spectrum of the background medium. For each wavelength pair (λ1, λ2), we obtain a measurement of the relative concentrations of the two chromophores, where the only required parameters are the extinction coefficients of the two chromophores and the ratio of the background scattering coefficients at λ1 and λ2. In a mixture of two test chromophores (blue food coloring dye and black India ink) contained in a 0.78-cm diameter cylinder, our spectral approach yielded relative concentrations values that were within 6% of their actual values. Although our paired-wavelength spectral approach is not generally applicable to any pair of chromophores, it is suitable for oxyhemoglobin and deoxyhemoglobin and is thus appropriate for oximetry of localized lesions in biological tissues.

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© 2007 Society of Photo-Optical Instrumentation Engineers

Citation

Ning Liu ; Angelo Sassaroli and Sergio Fantini
"Paired-wavelength spectral approach to measuring the relative concentrations of two localized chromophores in turbid media: an experimental study", J. Biomed. Opt. 12(5), 051602 (September 20, 2007). ; http://dx.doi.org/10.1117/1.2779349


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