Skin cancer is one of the most commonly diagnosed type of cancer. Its early diagnosis is essential for effective treatment. Nowadays in the clinical environment visual inspection followed by histological examination is state of the art. A large number of surgical procedures are still performed unnecessary. Hence an efficient and easy-to-use diagnostic tool can help to reduce this number.
Two methods which match the requirements on the resolution of some microns and penetration depth of some hundreds of microns are confocal microscopy and optical coherence tomography (OCT). Both methods can deliver a non-invasive 3D visualization of the human skin. While confocal microscopy offers a higher resolution, OCT has a higher penetration depth along with a short data acquisition time.
The EU project VIAMOS proposes a miniature, low cost, 3D OCT system, which combines swept-source OCT detection and MOEMS1 technologies, providing cross-sectional 3D tomograms of a skin volume of 8 x 8 x 0.5 mm³ with a resolution of 6 µm. To achieve this objectives, VIAMOS brings together academic institutions, research institutes and industrials partners, experienced in the field of MEMS2 & MOEMS, photonics & OCT, microscopy, system integration and dermatology. VIAMOS’s approach will enable a cheaper, portable OCT microsystem for early diagnosis of skin cancer.
Since 1991 OCT is one of the most investigated fields of non-invasive imaging techniques for medical applications. It is based on low coherence interferometry reaching a axial and lateral resolution of 3 to 15 µm and a penetration depth of 1 mm, in consequence OCT is a trade-off between ultrasound and confocal microscopy. The first approaches of OCT system were based on point-scanning system, allows to integrate the sensor via an optical fiber into an endoscopic and catheter-based imaging system. A fiber coupler splits the light into the sample and reference path. By scanning of a mirror in the reference path the zero delay plane of the low coherence interference is scanned through the sample, which gives the depth information of the sample. More recent OCT, called spectral or frequency domain OCT, provides advantages in higher sensitivity and faster signal acquisition, because of the full depth is scanned at one single shot. The depth information of the sample is than calculated by the inverse Fourier-Transform of the spectrally resolved interference fringes.
The current investigation fields in OCT are to decrease the measurement time while the sample volume increases. The concept of the VIAMOS project is the parallelization of the measurement system, which will be realized a micro lens array, each images a defined field of view within each pixel of the camera corresponds to on Z-Scan through the sample. The potential of MEMS and micro-optical technologies, exploited by VIAMOS, will open the possibility to perform similar instrumental tasks in a hand-held instrument.
1 MOEMS: Micro-Opto-Electro-Mechanical Systems
2 MEMS: Microelectromechanical systems
- Institute FEMTO-ST, UFR Sciences Médicales et Pharmaceutiques, Université de Franche-Comté, Besançon, France.
- VTT Technical Research Centre of Finland.
- Institut für Technische Optik, University Stuttgart, Germany.
- Fraunhofer-Einrichtung für Elektronische Nanosysteme, ENAS, Chemnitz, Germany
- Swiss Center for Electronics and Microtechnology, CSEM SA, Switzerland
- DermoScan GmbH, Regensburg, Germany
- Statice, Besançon, France
- J. Krauter, T. Boettcher, W. Lyda, W. Osten, N. Passilly, L. Froehly, S. Bargiel, J. Albero, S. Perrin, J. Lullin, C. Gorecki; “Optical design of a vertically integrated array-type Mirau-based OCT system”, Proc. SPIE 9132, 91320L, 2014; doi:10.1117/12.2054573