T-ray technology reveals what goes under your skin

A new method of analyzing skin structure using a type of radiation known as T-rays could help improve the diagnosis and treatment of skin conditions such as eczema, psoriasis and skin cancer.

Scientists from the University of Warwick and the Chinese University of Hong Kong (CUHK) have shown that by using a method that involves analyzing T-rays shot from different angles, they can construct a more detailed image of the structure of an area of skin and how hydrated it is compared to what current methods allow.

Their method is reported in Advanced Photonics Research and could provide a new tool for scientists and doctors to characterize skin properties in individuals, to assist in the management and treatment of skin conditions.

Terahertz (THz) radiation, or T rays, lies between infrared and WiFi on the electromagnetic spectrum. T-rays can see through many common materials such as plastics, ceramics, and clothing, making them potentially useful in non-invasive inspections. The low-energy photons of T-rays are also non-ionizing, which makes them very safe in biological settings, including safety and medical screening.

Only T-rays that pass through the outer layers of the skin (stratum corneum and epidermis) before being reflected can be detected, as those that travel deeper are too attenuated. This makes T-ray imaging a potentially effective way to monitor these outermost layers. To verify this, terahertz light is focused on the skin via a prism, to align the beam on a particular focal plane. Depending on the properties of the skin, that light will be reflected slightly differently. Scientists can then compare the properties of light before and after it enters the skin.

However, there are limitations in standard THz reflection spectroscopy, and to overcome them the scientists behind this new research have instead used ellipsometry, which involves focusing the T-rays at multiple angles on the same area of ​​the skin.

They successfully demonstrated that using ellipsometry they could accurately calculate the refractive index of the skin (which determines the speed at which the ray travels through it) measured in two directions perpendicular to each other. The difference between these refractive indices is called birefringence and this is the first time that the THz birefringence of human skin has been measured in vivo. These properties can provide valuable information on the amount of water present in the skin and help calculate the thickness of the skin.

Professor Emma Pickwell-MacPherson, from the Department of Physics at the University of Warwick and the Department of Electronics Engineering at CUHK, said: “We wanted to demonstrate that we could perform ellipsometric measurements in vivo in human skin and calculate the properties of the skin in imaging. of ordinary terahertz reflection, you have the thickness and the refractive index combined as a single parameter.Making measurements at multiple angles can separate the two.

“Hydrated skin will have a different refractive index than dehydrated skin. For people with skin disorders, we will be able to probe the hydration of their skin quantitatively, more than existing techniques. If you are looking to improve care products. For people with conditions such as eczema or psoriasis, we would potentially be able to make quantitative assessments of how the skin is improving with different products or to differentiate skin types.

“For skin cancer patients, THz imaging can also be used to probe the skin before surgery begins, to get a better idea of ​​how far a tumor has spread. Skin cancer affects skin cancer. properties of the skin and some of these are not visible since you are under the surface. “

Dr Xuequan Chen, first author of the study and postdoctoral fellow in the Department of Electronics Engineering at CUHK, said, “T-rays are known to be sensitive to the skin’s moisture level. However, we report that cellular structure stratum corneum also reacts to terahertz reflexes. Our technique allows us to sensitively probe this property of the structure, which provides complete information about the skin and is very useful for skin diagnosis. “

To test their method, the researchers asked the volunteers to place their arm over the imaging window of their T-ray equipment for 30 minutes, after acclimating to the ambient temperature and dryness of the laboratory. By holding their skin against the surface of the imaging window, they prevented water from leaking out of their skin in the form of sweat, a process called occlusion.

The researchers then took four measurements perpendicular to each other every two minutes for half an hour, so they could monitor the effect of the occlusion over time. Since T-rays are particularly sensitive to water, they could see a noticeable difference when water builds up in the skin, suggesting that the method could show a product’s effectiveness in keeping skin hydrated, for example.

Further research will look at improving process instrumentation and how it could work as a practical device.

Professor Pickwell-MacPherson said: ‘We have nothing really accurate to measure skin for doctors to use. Dermatologists need better quantitative tools to use and use easily.

“If it works well, you could go to a clinic, put your arm on a scanner, your occlusion curve would be plotted, and a product that fits your skin could be recommended. We could get more personalized medications and develop products for different skin responses. It could really fit the current focus on tailored medicine. ”