OCT images blood vessels beneath skin that feed cancer

Ashley N. Rice, ashley.rice@photonics.com

A noninvasive optical coherence tomography method that maps the network of tiny blood vessels in the epidermis in three dimensions might soon help doctors better diagnose, monitor and treat skin cancer.

Medical University Vienna scientists are the first to use the high-resolution imaging technique – previously used by ophthalmologists to image different parts of the eye – to visualize the network of blood vessels beneath the outer layer of skin that feed cancerous lesions. A laser light source developed at Ludwig Maximilian University was used to maximize image quality, enabling unprecedented high-speed imaging and operation at a near-infrared wavelength for better skin penetration.

“The condition of the vascular network carries important information on tissue health and its nutrition,” said Rainer Leitgeb, a Medical University Vienna researcher and the study’s principal investigator. “Currently, the value of this information is not utilized to its full extent.”

Healthy versus diseased skin vasculature: (a) A healthy network of blood vessels in the lower layer of skin on the palm of a hand. (b) Blood vessels supplying a basal cell carcinoma on the forehead. The effects of disease on the vascular system are evidenced by the branching pattern of vessels in image (b), with abnormally large vessels for a depth range similar to image (a). Both images show a 2 x 2-mm area. Courtesy of Medical University Vienna/Biomedical Optics Express.

Current techniques for skin disease diagnostics include visual inspection, dermatoscopy and/or high-resolution photography, and invasive biopsy followed by a histopathological exam.

“Contrary to our technique, visual inspection and photography do not provide depth-resolved information about the tissue structure, and their imaging depth range is limited,” Medical University Vienna doctoral candidate and the OCT system’s developer Cedric Blatter told BioPhotonics. “Our technique provides complementary functional information about the tissue health.”

“Our system combines high-speed imaging with a special illumination scheme for extended focus imaging based on Bessel beams,” Leitgeb told BioPhotonics. Such beams can reform, or heal, their shape, even if portions of them are blocked. “Standard imaging systems rely on Gaussian optics that impose a trade-off between axial resolution and depth of focus. Bessel beams, on the other hand, have the advantage that they do keep the transverse extension of the axial intensity distribution over a large depth range.” In this case, approximately 1 mm.

“After passing obstacles along the optical axis, the beam[s] recover their shape,” Leitgeb said. “In [the] case of imaging skin, it allows [one] to look past obstacles such as hairs that would otherwise obscure structures below.”

The system was tested on a variety of skin conditions, including a healthy human palm, dermatitis on the forehead, allergy-induced eczema on the forearm and two cases of basal cell carcinoma – the most common type of skin cancer – on the face. The network of vessels supplying blood to the tested lesions showed significantly altered patterns in comparison with healthy skin.

“We are currently in phase one of studying our system on selected patients for its diagnostic potential in a preclinical setting,” Leitgeb said. “It is difficult to give exact dates, but we are currently raising project money for translation of our system from bench to bedside.”

The method also could be used to diagnose other diseases that affect the perfusion and the vascular system in the skin.

“It is known, for example, that the microcirculation is altered in diabetes patients, and regular controls of periphery limbs such as toes are important to avoid amputation,” Leitgeb said. “The direct and easy access to the tissue perfusion and the vascular structure would, in this case, be of great help for early detection of suspicious alterations.”

The team is now working to increase the field of view “because we believe that the border of the lesion might give further insight on the tumor stage and growth,” Blatter said. Next, the researchers hope to improve the instrument’s portability so that they can reach any area of the body.

The research appeared in Biomedical Optics Express (doi: 10.1364/BOE.3.002636).