Medical physicists at the Medical University of Vienna have invented a non-invasive optical technique for detecting skin cancer or other skin diseases, which improves the diagnostic process and could ultimately reduce or even eliminate the necessity to take invasive tissue biopsies.
According to Cedric Blatter, PhD student at the Medical University of Vienna, the problem with taking tissue biopsies is that the tissue and tumour region is altered, meaning that cell proliferation occurs and scars remain. The new approach, based on a technique called optical coherence tomography (OCT), uses an advanced optics system to non-invasively map out the network of tiny blood vessels beneath the outer layer of patients’ skin, potentially revealing tell-tale signs of disease.
"Visualizing the blood supply to tumour regions in-situ could help for a better and early diagnosis as well as for treatment monitoring. Knowing the pathways, over which the tumour is fed, together with the total blood-supply, allows for an efficient target of the malignant tissue," says Blatter.
OCT uses an advanced optics system to non-invasively map out the network of tiny blood vessels beneath the outer layer of patients’ skin, potentially revealing tell-tale signs of disease
Optical coherence tomography
OCT is a non-invasive optical imaging technique that works on the principle of the “optical echolocation of backscattered infrared light.” As Blatter explains, the distance travelled by reflected light rays maps the structure of the sample under investigation.
The distance travelled by reflected light rays maps the structure of the sample under investigation.
"It is in fact the optical analogue to ultrasound imaging. However, OCT uses low-coherence interferometry to distinguish reflections occurring in depth or along the beam direction, such as to image a reflectivity depth-profile, also called A-Scan," he says.
As part of the European Commission project, the team collaborated with Ludwig Maximillian University in Munich, where a group led by Dr. Robert Huber built the fast wavelength tuning laser source, based on the concept of Fourier Domain Mode Locking.
"The centre wavelength of this source is 1300nm, which is less scattered in skin. The speed of this source reaches 440 000 A-scans per second, which helps to significantly reduce motion artefacts, such as loss of contrast for fine vascular details," says project leader Rainer Leitgeb, Professor of Medical Physics at the Medical University of Vienna.
"The light source, being of a super luminescent diode or a fast wavelength tuning laser, is of paramount importance in OCT…"
The team are currently performing preclinical testing of the method and are in the process of submitting new project funding applications.
"There are several improvements possible to the first prototype system in our lab. First, a larger field of view is desirable to cover larger lesion sites. Then, the display of the vasculature could be updated in real time employing fast graphic processing units. This is important for providing better guidance for the medical doctor to select the region of interest," explains Leitgeb.
"In current systems the information content provided by OCT is not fully exploited. We are convinced that the complementary metabolic information will significantly enhance the potential of OCT in medical diagnostics of skin diseases," he adds.
Written by Andrew Williams, Contributing Editor, Novus Light Technologies Today