Terahertz biosensor spots early signs of skin cancer

27 Feb 2024

Queen Mary device using THz metasurfaces distinguishes healthy from cancerous tissue.

A project at Queen Mary University of London has developed a novel biosensor using metasurfaces to detect terahertz radiation, designed to spot the onset of skin cancer.

Published in IEEE Transactions on Biomedical Engineering, the device could "usher in a new era of early cancer detection," according to the researchers.

The ability of THz radiation to provide spectroscopic data about living tissues in vivo is attractive, due to its largely non-ionizing and non-invasive nature.

Previous work in this area includes 2020 research at the University of Warwick into a novel ellipsometry technique, providing multiple complementary sets of spectral ratios and significantly boosting the performance of THz techniques when analyzing skin.

That project noted that a THz platform capable of quantitatively assessing the condition of skin could be useful in clinical scenarios for the monitoring of skin cancer, or to assess the effectiveness of medications and moisturizers.

The Queen Mary project aimed to design a sensor able carry out such a cancer diagnosis, distinguishing between the responses of healthy and malignant tissues under THz radiation. It used metasurfaces in the device's design to reduce the size and complexity of the sensor.

"Traditional methods for detecting skin cancer often involve expensive time-consuming CT, PET scans and invasive higher frequencies technologies," said Queen Mary's Shohreh Nourinovin. "Our biosensor offers a non-invasive and highly efficient solution, leveraging the unique properties of THz waves, a type of radiation with lower energy than X-rays and thus safe for humans, to detect subtle changes in cell characteristics."

Portable affordable sensors for more than cancer screening

Use of THz spectroscopy for this kind of diagnosis has in the past often relied solely on the different refractive index behavior of the two classes of cells; but other parameters such as transmission magnitude and Q-factor, a measure of the skin's physical resonance response, are likely to be equally valuable.

To access these alternative parameters and improve the sensitivity of the device, the project designed a THz metasurface based on asymmetric resonators on an ultra-thin and flexible dielectric substrate.

The device can then analyze a combination of parameters, including resonance frequency, transmission magnitude, and the distribution of the spectral response, according to the Queen Mary team. This approach "provides a richer picture of the tissue, allowing for more accurate differentiation between healthy and cancerous cells and to measure malignancy degree of the tissue."

In trials using a two-layer skin model, distinct frequency shifts of 40 and 20 GHz respectively were observed when basal cell carcinoma cancer were replaced by healthy cells, and when the density of basal cell carcinoma was increased from 1 x 10⁵ to 2.2 x 10⁵.

Integrating THz metasurfaces with this type of flexible, portable, reuseable sensor could make cancer screening a quicker and more comfortable procedure, according to the Queen Mary researchers, while also opening up new potential applications.

"The implications of this study extend far beyond skin cancer detection," commented Shohreh Nourinovin. "This technology could be used for early detection of various cancers and other diseases, like Alzheimer's, with potential applications in resource-limited settings due to its portability and affordability."