Accuracy and resolution of THz reflection spectroscopy for medical imaging

Abstract

The use of THz radiation as a potential tool for medical imaging is of increasing interest. In this paper three methods of analysis of THz spectroscopic information for diagnosis of tissue pathologies at THz frequencies are presented. The frequency-dependent absorption coefficients, refractive indices and Debye relaxation times of pure water and pure lipids were measured and used as prior knowledge in the different theoretical methods for the determination of concentration. Three concentration analysis methods were investigated: (a) linear spectral decomposition, (b) spectrally averaged dielectric coefficient method and (c) the Debye relaxation coefficient method. These methods were validated on water and lipid emulsions by determining the concentrations of phantom chromophores and comparing to the known composition. The accuracy and resolution of each method were determined to assess the potential of each method as a tool for medical diagnosis at THz frequencies.

Concentration analysis of breast tissue phantoms with terahertz spectroscopy

“…2 ε , ε ' , and ε '' have the highest correlation with the concentrations of all the phantom components. The high correlation of 2 ε with the lipid concentration in intralipid emulsions was also reported previously by [12]. …”

“…Similar to a previous study [12], a commercial water and lipid emulsion -Intralipid 20% (Sigma Aldrich, UK) is used to avoid difficulties in mixing oil and water effectively. The intralipid contains 20% of soybean oil stabilized with phospholipid.…”

“…Therefore, it is essential to seek an answer for the possibility of identifying tissue composition through the THz imaging data. A preliminary study of tissue composition has been conducted with water and lipid emulsions [12]. The authors employed three different methods -linear spectral decomposition, spectrally averaged dielectric coefficient, and Debye relaxation coefficient methods, to specify the sample composition.…”

Tutorial: Terahertz beamforming, from concepts to realizations

“…26 This is useful because many molecules in biology and chemistry are chiral and respond differently to left-and right-hand circularly polarized terahertz waves. [27][28][29] Terahertz-range imaging applications 30 such as safe, subdermal medical imaging, [31][32][33] security screening, 34 and non-destructive imaging of priceless artifacts and art 35,36 are envisaged, as terahertz waves are non-ionising, and can penetrate to a modest depth in soft tissues 37 and clothing. 38 Such non-contact imaging applications typically rely on some form of beam control-either fine beamfocusing 30,39 or Bessel beams, 40 to provide adequate resolution.…”

Terahertz wavefronts measured using the Hartmann sensor principle

“…Electromagnetic radiation in the THz frequency range is a relatively new, active research area and has peculiar characteristics that make it suitable for various applications for which the optics and microwave techniques are often unable to apply [8][9][10]. Although there have been many publications on the properties of THz radiation, until now the THz wavefronts have been rarely studied except for the wavefronts of short THz pulses [11].…”