In vivo quantification of the scattering properties of tissue using multi-diameter single fiber reflectance spectroscopy

Abstract

Multi diameter single fiber reflectance (MDSFR) spectroscopy is a non-invasive optical technique based on using multiple fibers of different diameters to determine both the reduced scattering coefficient (μs′) and a parameter γ that is related to the angular distribution of scattering, where γ = (1-g2)/(1-g1) and g1 and g2 the first and second moment of the phase function, respectively. Here we present the first in vivo MDSFR measurements of μs′(λ) and γ(λ) and their wavelength dependence. MDSFR is performed on nineteen mice in four tissue types including skin, liver, normal tongue and in an orthotopic oral squamous cell carcinoma. The wavelength-dependent slope of μs′(λ) (scattering power) is significantly higher for tongue and skin than for oral cancer and liver. The reduced scattering coefficient at 800 nm of oral cancer is significantly higher than of normal tongue and liver. Gamma generally increases with increasing wavelength; for tumor it increases monotonically with wavelength, while for skin, liver and tongue γ(λ) reaches a plateau or even decreases for longer wavelengths. The mean γ(λ) in the wavelength range 400-850 nm is highest for liver (1.87 ± 0.07) and lowest for skin (1.37 ± 0.14). Gamma of tumor and normal tongue falls in between these values where tumor exhibits a higher average γ(λ) (1.72 ± 0.09) than normal tongue (1.58 ± 0.07). This study shows the potential of using light scattering spectroscopy to optically characterize tissue in vivo.

Layer-by-layer assembled fluorescent probes in the second near-infrared window for systemic delivery and detection of ovarian cancer

“…In general, probes with longer emission wavelengths can be imaged with higher quality owing to reduced light scattering and tissue autofluorescence. In particular, light scattering decreases monotonically as emission wavelength increases (9,28,29). According to their fluorescence emission spectra, we chose optical filter sets of two 1,400-nm long pass + two 1,575-nm band pass, two 1,300-nm long pass + two 1,375-nm band pass, two 1,300-nm long pass, and two 1,100-nm long pass + two 1,125-nm band pass for DCNPs, QDs, SWNTs, and dye complex, respectively, to maximize each probe's signal-to-noise ratio (Table S1).…”

Modeling subdiffusive light scattering by incorporating the tissue phase function and detector numerical aperture

“…[7][8][9][10] However, recent work showed that a range of γ values (for the same μ 0 s , μ a , and d det ) can result in the same reflectance.…”

Development of thin skin mimicking bilayer solid tissue phantoms for optical spectroscopic studies

“…Each layer in the phantom is characterized by its intrinsic optical properties like absorption coefficient μ a (λ), scattering coefficient μ s (λ), anisotropy factor g(λ) and refractive index n(λ) as a function of wavelength λ(nm). The typical values of these parameters in the visible wavelength range were based on reported literature [25, [39][40][41][42][43][44][45][46][47][48]. Volume fraction of melanosomes which corresponds to the optical absorption coefficient μ aepi (λ) of the epidermis is taken as 2% (for light pigmented skin) for the present study [42].…”

“…Scattering coefficients μ s (λ) and anisotropy g(λ) of epidermal and dermal layers of normal tissues and dysplastic conditions were approximated using the relations given in literature [40]. Scattering properties of polystyrene microspheres mentioned in Table 1 is found to match with the scattering properties of both the layers [39,41,47]. Different concentrations of FAD representing normal and abnormal conditions [25,45] were also chosen for the current study as presented in Table 1.…”