Terahertz time-domain spectroscopy for non-invasive assessment of water content in biological samples

We apply terahertz time-domain spectroscopy for the quantitative non-invasive assessment of the water content in biological samples, such as Carpinus caroliniana tree leaves and pork muscles. The developed experimental terahertz time-domain spectroscopy system operates both in transmission and reflection modes. The Landau-Looyenga-Lifshitz-based model is used for the calculation of the water concentration within the samples. The results of the water concentration measurements are compared with the results of the gravimetric measurements. The obtained results show that the water content in biological samples can be measured non-invasively, with a high accuracy, utilizing terahertz waves in transmission and reflection modes

The impact of optical radiation of femtosecond duration on human glial cells

The paper presents the results of the studies of influence of optical radiation with wavelengths of 520 and 780 nm on human glial cells (U251) at the range of exposure times ∼ 1-15 min. It was found that after the first minute of irradiation at the wavelength of 780 nm, the relative number of apoptotic cells significantly increased. The result corroborates the concept of biological hazard of optical radiation for tumor cells, and suggests that the approach has a great potential in clinical application for the treatment of human glioma

Terahertz-to-infrared converters for imaging the human skin cancer: challenges and feasibility

PURPOSE: Terahertz (THz) medical imaging is a promising noninvasive technique for monitoring the skin's conditions, early detection of the human skin cancer, and recovery from burns and wounds. It can be applied for visualization of the healing process directly through clinical dressings and restorative ointments, minimizing the frequency of dressing changes. The THz imaging technique is cost effective, as compared to the magnetic resonance method. Our aim was to develop an approach capable of providing better image resolution than the commercially available THz imaging cameras. APPROACH: The terahertz-to-infrared (THz-to-IR) converters can visualize the human skin cancer by converting the latter's specific contrast patterns recognizable in THz radiation range into IR patterns, detectable by a standard IR imaging camera. At the core of suggested THz-to-IR converters are flat matrices transparent both in the THz range to be visualized and in the operating range of the IR camera, these matrices contain embedded metal nanoparticles (NPs), which, when irradiated with THz rays, convert the energy of THz photons into heat and become nanosources of IR radiation detectable by an IR camera. RESULTS: The ways of creating the simplest converter, as well as a more complex converter with wider capabilities, are considered. The first converter is a gelatin matrix with gold 8.5-nm diameter NPs, and the second is a polystyrene matrix with 2-nm diameter NPs from copper-nickel MONEL ® alloy 404. CONCLUSIONS: An approach with a THz-to-IR converter equipped with an IR camera is promising in that it could provide a better image of oncological pathology than the commercially available THz imaging cameras do

Tunable THz Graphene Filter Based on Cross-In-Square-Shaped Resonators Metasurface

The tunable terahertz (THz) Fano-resonant filter based on hybrid metal-graphene metamaterial was proposed. The optical parameters of metasurface with unit cell in the form of a cross-shaped graphene sheet in the center of a square gold ring were simulated by the finite element method using a surface conductivity model of a graphene monolayer. The narrowband modulation of the transmission by varying the Fermi level of the graphene and the position of graphene cross inside the metal ring was demonstrated. Simulation results were well explained theoretically using a three-coupled oscillator model. The proposed device can be used as a narrowband filter in wireless THz communication systems and sensing applications

Effective Medium Theory for Multi-Component Materials Based on Iterative Method

For biomedical applications in the terahertz band, composites such as macromolecule compounds, biotissues and phantoms are studied. A description of dielectric properties of composite materials using mathematical models has its own fundamental and technological importance. In this work, we present an iterative effective medium theory for multi-component materials. The model has good performance in describing composite materials with more than two components. The theory is evaluated by comparing with the complex permittivity of three different composite materials. A comparison with other commonly used models is given in the form of relative errors

Assessment of water content in biological samples by terahertz time-domain spectroscopy

The noninvasive measurement of water content in biological samples utilizing the terahertz waves is a promising tool for various biomedical applications. We introduce the method of water concentration measurement in biological samples by terahertz time-domain spectroscopy.</p

Agar and Silica Gel Based Biotissue-mimicking Phantoms in THz Frequency Range

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Gastrointestinal cancer diagnostics by terahertz time domain spectroscopy

Abstract Samples of fresh excised tissues obtained from patients who had undergone gastric cancer have been investigated. Samples consisted of cancer zone, normal zone and pathologically changed zone. Their optical properties and spectral features were investigated by terahertz time-domain spectroscopy (THz-TDS) in reflection mode. It was found that waveforms of reflected signals from normal and cancer tissues and their optical properties were well distinguished, so it can be concluded that it is possible to discriminate gastric cancer tissue from normal by using THz-TDS

Towards non-invasive reflection measurement of water content in biotissue by means of terahertz timedomain spectroscopy

Abstract We apply terahertz time-domain spectroscopy for the quantitative non-invasive assessment of water content in biological samples: tree leafs and pork muscles. The Landau-Looyenga-Lifshitz-based model is used for the calculation of water concentration within the samples. The obtained results show that water content in biological samples can be measured utilizing terahertz waves in transmission and reflection modes

Influence of the geometric parameters of the electrical ring resonator metasurface on the performance of metamaterial absorbers for terahertz applications

In this paper, the effect of the geometrical parameters of an electrical ring resonator(ERR) on the total absorptivity of metamaterial absorbers is analyzed. In particular, the effect of electrical ring resonator parameters, dielectric layer(spacer) thickness and electrical ring resonator thickness on the absorber of metamaterials are analyzed in detail. On this basis, the orthogonal experiment is set up to analyze the combined effects of several parameters and finally obtain the theoretical absorptivity of metamaterials. Based on the above results, the principle prototype of two metamaterial absorbers is prepared. The results show that the narrowband absorptivity of the prototype is higher than 98%, which provide guidance for the design of high performance absorber