Terahertz imaging of human skin pathologies using laser feedback interferometry with quantum cascade lasers

Abstract

Early detection of skin pathologies with current clinical diagnostic tools is challenging, particularly when there are no visible colour changes or morphological cues present on the skin. In this study, we present a terahertz (THz) imaging technology based on a narrow band quantum cascade laser (QCL) at 2.8 THz for human skin pathology detection with diffraction limited spatial resolution. THz imaging was conducted for three different groups of unstained human skin samples (benign naevus, dysplastic naevus, and melanoma) and compared to the corresponding traditional histopathologic stained images. The minimum thickness of dehydrated human skin that can provide THz contrast was determined to be 50 µm, which is approximately one half-wavelength of the THz wave used. The THz images from different types of 50 µm-thick skin samples were well correlated with the histological findings. The per-sample locations of pathology vs healthy skin can be separated from the density distribution of the corresponding pixels in the THz amplitude–phase map. The possible THz contrast mechanisms relating to the origin of image contrast in addition to water content were analyzed from these dehydrated samples. Our findings suggest that THz imaging could provide a feasible imaging modality for skin cancer detection that is beyond the visible.

Terahertz in vivo imaging of human skin: Toward detection of abnormal skin pathologies

“…The results of this first-in-man clinical imaging study are in line with our earlier ex vivo experiments with fixed sectioned skin samples, 31 despite the differences in imaging orientation (i.e., longitudinal vs cross-sectional). Notably the presence of water in vivo does not necessarily hinder the separation of lesion types compared to dehydrated ex vivo samples.…”

“…The contrast of the two naevi in the THz images is not as evident as in the visible photo, which might be owing to no notable fingerprint of the melanin content at the emission frequency from the QCL at 2.85 THz. 31 The images in Fig. 1(b) show a participant with photodamaged skin on his arms and back, which can be seen from the skin texture in both the visible and THz images for a skin lesion located on the upper arm.…”

THz‐Wave Absorption Properties of Organic–Inorganic Hybrid Perovskite Materials: A New Candidate for THz Sensors

“…In the 0.5-2.5 THz, notably, there is no report for the phonon mode originating from the CH 3 NH 3 cation. Consistently, A. M. A. Leguy, et al found no molecular-based phonon mode confirmed by Raman spectroscopy experiment [87] Copyright 2023, published by Optica Publishing Group. Images for "Breast cancer": Reproduced with permission.…”

“…Images for “Skin cancer”: Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0). [ 87 ] Copyright 2023, published by Optica Publishing Group. Images for “Breast cancer”: Reproduced with permission.…”

“…Terahertz sensing applications based on the physical sensitivity of THz-wave. Images for "Skin cancer": Reproduced under the terms of the CC-BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0) [87]. Copyright 2023, published by Optica Publishing Group.…”