title: Fluorescence spectra provide information on the depth of fluorescent lesions in tissue.
abstract: The fluorescence spectrum measured from a fluorophore in tissue is affected by the absorption and scattering properties of the tissue, as well as by the measurement geometry. We analyze this effect with Monte Carlo simulations and by measurements on phantoms. The spectral changes can be used to estimate the depth of a fluorescent lesion embedded in the tissue by measurement of the fluorescence signal in different wavelength bands. By taking the ratio between the signals at two wavelengths, we show that it is possible to determine the depth of the lesion. Simulations were performed and validated by measurements on a phantom in the wavelength range 815-930 nm. The depth of a fluorescing layer could be determined with 0.6-mm accuracy down to at least a depth of 10 mm. Monte Carlo simulations were also performed for different tissue types of various composition. The results indicate that depth estimation of a lesion should be possible with 2-3-mm accuracy, with no assumptions made about the optical properties, for a wide range of tissues.
authors.affiliation: Department of Physics, Lund Institute of Technology, P.O. Box 118, SE-22100 Lund, Sweden. js604@cam.ac.uk
authors.forename: Johannes
authors.initials: J
authors.lastname: Swartling
authors.forename: Jenny
authors.initials: J
authors.lastname: Svensson
authors.forename: Daniel
authors.initials: D
authors.lastname: Bengtsson
authors.forename: Khaled
authors.initials: K
authors.lastname: Terike
authors.forename: Stefan
authors.initials: S
authors.lastname: Andersson-Engels
mesh_terms: D000465:Algorithms; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D009010:Monte Carlo Method; D009391:Nephelometry and Turbidimetry / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence / Q000295:instrumentation / Q000379:methods*