Now, terahertz (THz) technologies have been actively studied and applied in various biomedical applications including cancer diagnosis. It is related with unique features of THz spectroscopy, such as high sensitivity to water and other polar molecules, the presence of resonant peaks of various biomolecules in the THz frequency range, harmless of THz radiation to biological tissues. In this work, we have investigated different types of gastric tissues using THz spectroscopy and obtain refractive indices in the frequency range from 0.2 to 1 THz. Fourier transform infrared spectroscopy (FT-IR) was also applied in order to see what’s components of tissues make the most significant contribution in optical response and, therefore, allow to discriminate cancer.
Significance: A new concept of a biotissue phantom for terahertz (THz) biomedical applications is needed for reliable and long-term usage.
Aim: We aimed to develop a new type of biotissue phantom without water content and with controllable THz optical properties by applying graphite powders into a polyvinyl chloride plastisol (PVCP) matrix and to give a numerical description to the THz optical properties of the phantoms using the Bruggeman model (BM) of the effective medium theory (EMT).
Approach: The THz optical properties of graphite and the PVCP matrix were measured using THz time-domain spectroscopy, which works in the frequency range from 0.1 to 1 THz. Two phantoms with 10% and 12.5% graphite were fabricated to evaluate the feasibility of describing phantoms using the EMT. The EMT then was used to determine the concentration of graphite required to mimic the THz optical properties of human cancerous and healthy oral tissue.
Results: The phantom with 16.7% of graphite has the similar THz optical properties as human cancerous oral tissue in the frequency range of 0.2 to 0.7 THz. The THz optical properties of the phantom with 21.9% of graphite are close to those of human healthy oral tissue in the bandwidth from 0.6 to 0.8 THz. Both the refractive index and absorption coefficient of the samples increase with an increase of graphite concentration. The BM of the EMT was used as the numerical model to describe the THz optical properties of the phantoms. The relative error of the BM for the refractive index estimation and the absorption coefficient is up to 4% and 8%, respectively.
Conclusions: A water-free biotissue phantom that mimics the THz optical properties of human cancerous oral tissue was developed. With 21.9% of graphite, the phantom also mimics human healthy oral tissue in a narrow frequency range. The BM proved to be a suitable numerical model of the phantom.
Non-invasive diagnostics methods are very helpful for cancer diagnosis and they are a research hotspot in the field of biomedicine. Terahertz (THz) photonics is an emerging technology that can be applied in the field of medical diagnostics. This is due to unique features of THz radiation such as harmlessness to biological tissues, strong absorption by water, ability to identify various biomolecules, etc. In this work we have investigated different types of normal and cancer fresh tissues of the stomach using terahertz time domain spectroscopy in reflection mode. Refractive indices of mucous, serous and tumor stomach tissues were obtained in the frequency range of 0,2 - 1 THz. These optical properties are higher for cancer tissue than for mucosa and lower than for serosa. Thus possibility of discrimination of tumor from normal stomach tissue was demonstrated. This study has practical significance for the field of clinical cancer diagnosis and will help to better understand the specifics of the method of pulsed THz spectroscopy applicable to this field.
This paper presents qualitative analysis of terahertz time-domain spectroscopy application for cancer diagnosis by measurement of the optical properties and spectral characteristics of cancer cells. For this purpose, the cultivation of two cancer cells, U-251 (glioblastoma brain) and A549 (lung adenocarcinoma), were carried out, then their refractive index, absorption coefficient and dielectric constant were measured, and the optical properties of tumor cells were compared with the optical properties of healthy cells (fibroblasts). Tumor cells contain more OH-components in comparison with healthy cells. Since terahertz radiation is heavily absorbed by water, there are differences in the spectra of healthy and oncological cells. To obtain the optical properties and spectral characteristics of the researched objects, a terahertz time-domain spectroscopy method in the transmission mode was used. The researched cell lines were cultured in vitro. Optical properties and spectral characteristics of the samples were calculated by the thin film method and Fourier transform. The results show the differences of refractive index, absorption coefficient and dielectric permittivity between the oncological cell lines U- 251, A549 and the healthy cells in the frequency range 0.2-1 THz. It was found that cancer cells have higher values of refractive indices and absorption coefficients than those of healthy cells. Brain glioblastoma (U-251) has a transmission peak at the frequency of 0.24 THz. The results obtained in this work can form the basis for the diagnosis of brain and lung cancer with the use of terahertz time-domain spectroscopy.
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