Scanner goes skin deep to reveal the secrets of psoriasis

The scanner is said to provide clinically relevant information, such as the structure of skin layers and blood vessels, without the need for contrast agents or radiation exposure.

A team of researchers from Helmholtz Zentrum München and the Technical University of Munich (TUM) describe the technology in Nature Biomedical Engineering.

Psoriasis is an inflammatory skin disease that is characterised by patches of severely scaling skin. The disease is estimated to affect between ten and fifteen million people in the European Union.

Currently, doctors assess the severity of the disease based on visual assessment of features of the skin surface, such as redness or thickness of the flaking skin.

"Unfortunately, these standards miss all parameters that lie below the surface of the skin, and may be subjective," said Dr Juan Aguirre, group leader at the Institute of Biological and Medical Imaging (IBMI) at the Helmholtz Zentrum München. "Knowing the structure of the skin and vessels before treatment can provide the physician with useful information.”

With the raster-scan optoacoustic mesoscopy (RSOM) technique, a weak laser pulse excites the tissue of interest, which then absorbs energy and heats up minimally. This causes momentary tissue expansion, which generates ultrasound waves. The scientists then measure these ultrasound signals and use this information to reconstruct a high resolution image of what lies under the skin. While developing the method, the scientists were able to reduce the size of the scanner to a handheld device.

"This technology, which is easy to use and does not involve any radiation exposure or contrast agent, is allowing us to acquire the first new insights into the disease mechanisms. It also facilitates treatment decisions for the physicians," said Prof Dr Vasilis Ntziachristos, director of the IBMI at the Helmholtz Zentrum München and Chair of Biological Imaging at the Technical University of Munich.

In their paper, the scientists are said to have demonstrated RSOM's performance by examining cutaneous and subcutaneous tissue from psoriasis patients. RSOM allowed them to determine several characteristics of psoriasis and inflammation, including skin thickness, capillary density, number of vessels, and total blood volume in the skin.

They compiled these to define a novel clinical index (a value that includes several diagnostic parameters that allow estimates of the severity of a disease) for assessing psoriasis severity that may be superior to the current clinical standard because the new index also takes into account characteristics below the skin surface.

The researchers now plan to use the same imaging method to assess other diseases such as skin cancer or diabetes.