Using a portable terahertz spectrometer to measure the optical properties of in vivo human skin

An empirical formula for temperature adjustment of complex permittivity of human skin in the terahertz frequencies

“…The common standard for live human skin studies is the use of the thin skin on the palmar aspect of the forearm, the “volar forearm” (e.g., Pennes [], Sivamani et al []). As there are only 3 in‐vivo data points available in THz studies derived unequivocally from the “volar forearm” [Pickwell et al, ; Echchgadda et al, ; Zaytsev et al, ], it is impractical to isolate the study to this area of the body. The low number of points necessitates the use of data from all sites reported as “thin skin.” This results in a greater variability of temperature.…”

“…In‐vivo “thin skin” data for the range 0.3–1.0 THz are available from six papers [Pickwell et al, ; Echchgadda et al, ; Fan et al, ; Zaytsev et al, , , ]. For 1.2 THz, published data are found in three papers [Pickwell et al, ; Echchgadda et al, ; Zaytsev et al, ] and for 1.5 THz only two papers exist [Pickwell et al, ; Zaytsev et al, (extrapolated from 1.4 THz)]. No surface skin temperature was specified for any of the data points.…”

“…Published in‐vivo data which are unequivocally derived from human “thick skin” are available from only two papers. There are three data points over the range 0.3 THz − 1.2 THz (“palm” [Echchgadda et al, ], “hand” and “heel” [Zaytsev et al, ]), and two data points at 1.5 THz (extrapolated from 1.4 THz, “hand” and “heel,” [Zaytsev et al, ]). No excised thick skin data are available.…”

Frequency-dependent skin penetration depth of terahertz radiation determined by water sorption–desorption

“…However, THz absorption coefficients that are derived from reflected THz waveforms cannot provide the exact skin penetration depth of THz radiation. The issue is that the Fresnel reflection principle of a single-layer skin surface, used to analyze the reflected waveforms, ignores wave interference in the multilayered internal structure of the skin [12]. Moreover, the frequency-dependent skin penetration depth of THz radiation has not been explored through reflective THz-TDS.…”

THz Time-Domain Spectroscopy of Human Skin Tissue for In-Body Nanonetworks

“…In past human skin dielectric properties have been studied extensively within the MHz to GHz range, however, limited studies are presented on animal and human tissue dielectric properties in the THz domain using Time Domain Spectroscopy (TDS) [1][2][3]. Earlier characterization techniques reported [4][5][6] were based on contact probe technique, which calculates the reflection coefficient using network analyzer.…”