Correlation-induced spectral changes in tissues

Abstract

We report experimental evidence of correlation-induced spectral changes in biological tissues. The overall spectral shift in our transmission measurements is to the red and the mean wavelength of the original spectrum is up 10% larger. These results indicate that the spectral changes due to elastic scattering are significant and likely to hinder all spectroscopic measurements based on the inelastic (i.e., emission and absorption) interaction between light and tissues. Thus, simultaneous morphology and spectral measurements are required for accurate measurements spectroscopic information.

Breakthroughs in Photonics 2013: Quantitative Phase Imaging: Metrology Meets Biology

“…In the past two decades, QPI has found numerous applications to biology: cell membrane dynamics [34], [35], intracellular transport [36], [37], cell tomography [29]- [31], [33], blood testing [34], [35], [38]- [50], tissue refractometry, scattering and diagnosis [51]- [58]. Below we highlight some recent breakthroughs in QPI applications.…”

Fourier spectrum analysis of full-field optical coherence tomography for tissue imaging

“…Thus, at the microscopic level the spatial distribution of tissue elements and their refractive indices which are the corresponding optical description of microscopic structure of tissue are continuous. Recognizing that the random characteristic of the refractive index requires statistical description methods, the concept of a spatial correlation function of the refractive index [2,24,25,[27][28][29][30][31][32][33] or the dielectric permittivity [34] was then used to model the microscopic structure of tissues. At present, several forms of the refractive index correlation function have been proposed to describe the tissue inhomogeneities among which the most general one is the Whittle-Matérn correlation function family which can be expressed in terms of three parameters, the length scale of refractive index correlation distance L o , the parameter m that describes the form of the correlation function and the variance of the refractive index fluctuation δn 2 [25,35].…”

“…In fact, the angular distribution of the scattered light is determined by the Fourier transform of the spatial correlation function of the refractive index or dielectric permittivity which randomly fluctuates with position. And the possible range of the Fourier components that can be measured is determined by the range of both the wavelengths of the light sources and the angles of the observation [24][25][26][27][28][29][30][31][32][33].…”

Spectral shifts of evanescent waves generated by the scattering of polychromatic light in the near field

“…Literature in this area has been particularly concerned with changes in the spectrum of light waves scattered by anisotropic and quasi-homogeneous mediums [15][16][17]. Very recently, correlation statistics on how being scattered in biological tissues influences the light spectrum have been revealed through implementation of theoretical and experimental means [18,19].…”

“…(19), Fig. 1 illustrates the dependence of the normalized spectra of evanescent waves in the near field on the ESSP values of the scatterer with the on-axis point, ρ 0, taken into account.…”