Studying brain glioma model heterogeneity using terahertz pulsed spectroscopy and solid immersion microscopy

Abstract

Terahertz (THz) technology went through rapid development during the past few decades [1]. Nowadays, it offers novel opportunities in the label-free diagnosis of malignant and benign neoplasms with different nosologies and localizations [2–4]. THz spectroscopy and imaging were studied as innovative tools for the intraoperative label-free diagnosis of brain gliomas, aimed at ensuring their gross-total resection [5–8]. Nevertheless, it is still far from clinical appli-cations due to the limited knowledge about the THz-wave–brain tissue interactions. In this work, rat glioma model 101.8 was studied ex vivo using both the THz pulsed spectroscopy and the 0.15λ-resolution THz solid immersion microscopy (λ is a free-space wavelength). The consid-ered homograft model mimics glioblastoma, possesses heterogeneous character, unclear mar-gins, and microvascularity [9]. Using the portable THz pulsed spectrometer [10, 11], effective THz optical properties of brain tissues were studied, as averaged within the diffraction-limited beam spot. Thus, measured THz optical properties revealed a persistent difference between in-tact tissues and a tumor, along with fluctuations of the tissue response over the rat brain. Next, glioma model 101.8 was studied using novel THz imaging modality – the continuous-wave re-flection-mode THz solid immersion microscopy adapted for imaging of soft biological tissues [12–14]. The observed THz microscopic images showed heterogeneous character of brain tis-sues at the scale posed by the THz wavelengths, which is due to the distinct response of white and gray matters, the presence of different neurovascular structures, as well as due to the ne-crotic debris and hemorrhage in a tumor. Such heterogeneities might significantly complicate delineation of tumor margins during the intraoperative THz neurodiagnosis. The presented re-sults for the first time pose the problem of studying the inhomogeneity of brain tissues that causes scattering of THz waves, as well as the urgent need to use the radiation transfer theory for describing the THz-wave—tissue interactions.

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Speaker

Anna S. Kucheryavenko
Prokhorov General Physics Institute of RAS; Institute of Solid State Physics of RAS
Russia

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