Poladerme: the device that puts the skin in the light

The skin is the largest organ in the human body, and a key indicator of a person's state of health. Its study can reveal a wide range of conditions, from benign lesions to melanomas. However, dermatological diagnosis is still very often based on conventional technologies. Jihad Zallat, Christian Heinrich and researchers from the ICube laboratory's "Optical Imaging" theme, supported by SATT Conectus Alsace, have developed an imaging device to aid dermatological diagnosis.

Complementary expertise

Operating such a device requires a wide range of scientific skills, as the data from the imager must be processed and analyzed. " At the ICube laboratory, I developed polarimetric optical imaging devices, while Christian worked on data processing and statistical learning," recalls Jihad Zallat.

After considering a number of applications, it was finally decided to focus on dermatology. This project was supported by SATT Conectus, and led to the Dermapol prototype.

The research team was then joined by an industrial partner, the French company ARCHOS, which helped accelerate the development of the solution. This collaboration led to the creation of the Poladerme start-up in 2021.

Going beyond the limits of the traditional dermatoscope

The approach used in dermatological examinations is essentially based on visual examination, using a dermatoscope. This device is a magnifying glass, equipped with light sources, and in some cases polarizing filters to improve contrast by eliminating unwanted reflections. The doctor may then decide to perform a biopsy, if necessary.

" This approach can be perfected, as it is based on observation of the skin's surface. No information from the deeper layers of the skin is directly taken into account," emphasizes Jihad Zallat. " The practitioner bases his diagnosis on the appearance (shape, color, size, etc.) of the lesion and its evolution. Poladerme aims to enrich the information available to the practitioner.

High-tech skin imaging devices have also been developed, but these are often expensive, complex and analyze a restricted field of view. Their distribution is therefore limited. Poladerme offers affordable, easy-to-use equipment that can analyze a macroscopic field of view. This equipment will eventually be used by general practitioners, speeding up the handling of suspected cases by dermatologists.

Light and skin

The device developed by Poladerme is a new-generation dermatoscope that exploits the light field at different wavelengths. " Varying the wavelength allows us to probe the skin at different depths," explains Jihad Zallat. " Blue light gives surface information, while infrared gives access right down to the dermis. " The images, captured by five on-board cameras, provide information invisible to the naked eye, down to a depth of just a few millimeters.

Poladerme is a spectropolarimetric instrument. It measures the polarization state of light as a function of wavelength, polarization being defined by the orientation of the electric field of the light wave. The device includes different light sources, each polarized in a specific way, as well as sensors, each with its own polarization analysis state. This structure makes it possible to exploit a wide range of skin probing states.

How can dermatologists benefit from spectropolarimetry? " Light-tissue interaction modifies the polarization state of the incident wave, " explains Jihad Zallat. " This change bears the signature of the skin structure, and therefore of the lesion. The first clinical trials thus enabled us, by means of a complete survey of the area studied, to highlight different polarimetric signatures between healthy tissue and lesioned tissue, on the one hand, but also between lesions of distinct types.

A unique database under construction

The images collected need to be processed and analyzed. This is wheremachine learning algorithms, a branch of artificial intelligence, come into play. " The database will be made up of Poladerme images, each associated with a biopsy," explains Christian Heinrich. " When new data arrives, it will be compared with the reference database. This will enable us to suggest probable pathologies.

Poladerme is based on an innovative imaging method. No such database exists. " That's precisely what we're going to do now: produce a database linking biopsies and spectropolarimetric images ", says Christian Heinrich. " In the long term, this database will represent considerable added value for dermatologists.

This crucial stage in the life of Poladerme has now begun. After more than a year's joint work with the ARCHOS engineering team, and the filing of a patent for the device, the first functional devices have been produced and delivered. The database is now being built up, thanks to the first practitioners using the equipment.

From dermatology to cosmetology

In addition to applications in medical dermatology, spectral polarization imaging can be a relevant tool in cosmetics. In this context, the aim is to establish a personalized assessment of the skin's state of health, in order to propose appropriate skin care products. " In the longer term, we hope to be able to provide a 3D image of the skin, its relief and its different layers ", reveal Jihad Zallat and Christian Heinrich. A promising new application, which we'll be coming back to in greater detail shortly, on the Carnot Télécom & Société numérique website.