Terahertz spectroscopy probes cellular structure of skin

 

Emma MacPherson: versatile THz technology

https://optics.org/news/11/12/1

University of Warwick and Chinese University of Hong Kong project could assist in skin cancer diagnosis.

Terahertz radiation, falling between the infrared and microwave regions of the spectrum, is attractive for in vivo applications due to its non-invasive and non-ionizing nature.

The limited penetration depths of THz radiation is thought to make it particularly suitable for analysis of the skin, diagnosing burns, scars and cancers.

However the complicated nature of living systems has to date presented a challenge, preventing current THz platforms from obtaining the accurate reflections from target tissues needed to build up images of the skin.

A project at the University of Warwick and the Chinese University of Hong Kong (CUHK) has now developed a THz platform intended to significantly enhance the characterization capabilities of THz spectroscopy, and published its study in Advanced Photonics Research.

The breakthrough involves a novel ellipsometry technique, providing mutliple complementary sets of spectral ratios and significantly boosting the performance of the technique.

A basic ellipsometry approach involves calculating the refractive index of target tissues measured in two directions at right angles to each other. The difference between these refractive indices is termed birefringence, and this is the first time that the THz birefringence of human skin has been measured in vivo according to the project. These properties can provide valuable information on how much water is in the skin and enable the skin thickness to be calculated.

"We wanted to show that we could do in vivo ellipsometry measurements in human skin and calculate the properties of skin accurately," said project leader Emma Pickwell-MacPherson of CUHK's terahertz research group.

"In ordinary terahertz reflection imaging, you have thickness and refractive index combined as one parameter. By taking measurements at multiple angles you can separate the two."

Tailored medicine from THz spectroscopy

The project's experimental platform employed a double-prism architecture mounted on a motorized stage, to provide two alternative optical paths and effectively allow four complementary sets of spectral ratios to be collected from the target.

After initial trials on a model of skin and its outer layer, or stratum corneum (SC), the project applied its platform to the forearms of five human volunteers, and found that the properties of the SC components and the epidermis could be computationally extracted from the spectral data using an algorithm.

The THz dispersion and birefringence sensitivity parameters are effectively probes for the level of hydration and the cellular inhomogeneity in the skin, according to the project, producing results in good agreement with microscope images and the observed biological processes taking place in the SC layer.

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 inherent sensitivity to water molecules could also allow the technique to detect areas of skin where the water circulation is different from the surrounding areas, potentially an early sign of problems.

"If this works well you could go into a clinic, put your arm on a scanner, your occlusion curve would be plotted and a suitable product for your skin could be recommended," commented Emma Pickwell-MacPherson. "We could get more tailored medicine and develop products for different skin responses. It could really fit in with the current focus on tailored medicine.”

Faster detection of hidden objects by new terahertz sensor

http://phys.org/news/2015-07-faster-hidden-terahertz-sensor.html#jCp
by Tom Frew

A new type of sensor, that is much faster than competing technologies used to detect and identify hidden objects, has been developed by scientists at the University of Warwick.

Called 'Q-Eye', the invention senses radiation across the spectrum between microwaves and infra-red, known as the Terahertz (THz) region of the spectrum – a goal that has challenged scientists for over 30 years. It works by detecting the rise in temperature produced when electromagnetic radiation emitted by an object is absorbed by the Q-Eye sensor, even down to the level of very small packets of quantum energy (a single photon).

The device could help address the weaknesses reported earlier this month in America's airport security, where mock weapons and explosives were smuggled through airports, undetected in 95% of cases. It may also prove useful in discovering concealed goods in the retail industry or for non-destructive monitoring, for example quality control in drugs or food. Other applications include astronomical and climate science observations and medical diagnosis.

Professors in Warwick's Nano-Silicon Group, Physics Department, Evan Parker and Terry Whall, led the team which developed the device. Professor Parker commented, "We were very surprised when our first very crude prototype showed such impressive speed and detection performance  and our initial calculations indicated world-beating detector capability – all this and using silicon."

Made using standard silicon processes, large numbers of detector chips containing designs matched to a particular application can easily be fabricated on large (300mm) wafers with great uniformity, setting it apart from existing technologies.

The patented device involves a thin film of aluminum deposited on top of a silicon layer placed under strain, used to create an electronic cooling (e-cooling) process. The electrons in the silicon layer are so isolated from the silicon lattice they become highly sensitive to incoming radiation. This revolutionary e-cooling process is the secret to Q-Eye sensor's exceptional performance, enabling fast imaging and material identification.

Professors Parker and Whall are currently working on a demonstrator of the device, having been awarded a £100,000 Smart award from Innovate UK. The work is moving out of academic research into the commercial world, offering opportunities for partnership and investment. Companies involved in the personnel screening market have already expressed interest in the Q-Eye device.

Warwick Ventures, Warwick's technology transfer business, has helped the professors to create a spin-out company, Q-Eye Ltd, to develop and market the technology. Melody Stokes, Warwick Ventures Business Development Manager, and Phil O'Donovan, Warwick alumnus and a Cambridge based business angel, are working with the academics to build the commercial team, secure commercial partners and raise funding to develop the first commercial prototypes.

Melody Stokes adds: "We're delighted to have distinguished Warwick alumnus Phil O'Donovan advise the team. He brings invaluable experience of developing early-stage technology into scalable businesses. The global market for devices that operate in the THz region is growing at around 26% year on year, so Q-Eye is well placed to support the UK's strategic lead in the sector. A longer term opportunity lies in quantum computing, set to revolutionize the way we handle and encrypt data."