Terahertz scattering in biological tissues: spherical and cylindrical scatterers
A. S. Kucheryavenko1,2, I. N. Dolganova1,2, N. V. Chernomyrdin1, and K. I. Zaytsev1
1 – Prokhorov General Physics Institute of the Russian Academy of Sciences, Russia
2 – Osipyan Institute of Solid State Physics of the Russian Academy of Sciences, Russia
Abstract
Terahertz (THz) technology has advanced rapidly over the past few decades. Currently, THz waves find applications across various fields of biophotonics and medicine.The preferred approach in most of these applications involves extracting the permittivity of the sample from reflectance or transmittance spectra. Additional information about sample composition can be obtained by applying appropriate effective medium models. Meanwhile, recent developments in high-resolution THz technology have enabled the visualization of wavelength-scale heterogeneity in different types of biological tissues, which can lead to Mie scattering. These advances have prompted further research into developing predictive models to relate heterogeneous structures in biological samples to THz scattering measurements and to explain such observations.
The first step of our study involved developing a phantom containing spherical, non-absorbing scatterers of subwavelength diameter embedded in a strongly absorbing matrix. Analytical methods based on Lorentz-Mie scattering theory predicted a non-Rayleigh scattering regime. However, we theoretically discovered and experimentally confirmed that the effective optical properties of the proposed phantom are still determined by the effective medium formalism across a wide range of scatterer diameters and volume fractions.
The next step of our study focused on an anisotropic system of cylindrical non-absorbing scatterers, also embedded in a strongly absorbing matrix. Analytical methods derived from Lorentz-Mie theory similarly predict a non-Rayleigh scattering regime and a weak dependence on radiation polarization direction. However, experimental data demonstrated the influence of medium anisotropy on the resulting reflection spectra. This necessitates the development of a polarization-sensitive model to describe radiative transfer in such systems.
Speaker
Anna S. Kucheryavenko
Osipyan Institute of Solid State Physics RAS (ISSP RAS)
Russia
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