Images from light

The topic

Patients' quality of life can be improved if diseases can be detected at a very early stage, when treatments are most likely to be successful and pathological organ changes are still reversible: ideally, detection should be non-invasive to avoid complications – such as using light waves!

The starting point for the research conducted by Rainer Leitgeb and his team was optical coherence tomography (OCT), a technique that was significantly co-developed and refined by several Christian Doppler Laboratories. The CD Laboratory for Innovative Optical Imaging and its Translation to Medicine, headed by Head of Laboratory Leitgeb, conducted research into improving medical, non-invasive diagnostic methods with the aid of light, in particular OCT. In the process, new imaging diagnostic methods with great advantages for doctors and patients were researched and developed for various medical fields: ‘Light for an improved quality of life’ is the laboratory's motto.

Example: Retinal diseases

OCT is particularly well suited for the early detection of retinal diseases: it can be used to generate high-resolution depth-cut images of the tissue – without contact! Leitgeb and his team worked towards achieving even higher resolution of the images obtained using this method: high enough to make individual photoreceptor cells in the living eye visible.

This is a very difficult task, as on the one hand the retina must be viewed through the small pupil of a moving eye, and on the other hand the eye itself is often affected by visual impairments such as myopia or astigmatism, which makes imaging even more difficult. However, the combination of fast parallel imaging of multiple points in the eye and new digital signal processing techniques made it possible to overcome all these obstacles.

Example: Cataracts

Eye measurement using OCT allows the length of the eye to be determined without contact, precisely, easily and with a low risk of infection, for example for planning cataract surgery, in which the cloudy lens of the eye is replaced with an artificial lens. But although easily preventable through simple surgery, cataracts are the leading cause of blindness worldwide – often due to a lack of availability of modern, often bulky and expensive equipment in medically underserved regions of the world.

The CD Laboratory therefore investigated alternative, far more cost-effective light sources that could also be used in very compact devices. And indeed, the CD Laboratory was able to develop a method that uses an easily available light source that is already used for facial recognition in mobile phones, with annual sales in the millions: this enables point-of-care testing in eye measurement (e.g. directly in the ophthalmologist's office or in the patient's home).

Example: Tumours brought to light

The successful removal of brain tumours is also crucial for patients' prognosis and quality of life. An important development in this area is the use of fluorescent markers that contrast tumour areas with healthy tissue. Unfortunately, low-grade tumours are difficult to distinguish from healthy tissue, which is why (in collaboration with neurosurgeon Georg Widhalm) research was conducted in the CD Laboratory to refine this method.

To this end, the suitability of fluorescence lifetime for contrasting tumours in brain tissue was investigated using tissue biopsies: When fluorescent dyes are illuminated, the light emission decreases at a characteristic rate after the illumination is switched off. It was shown that measuring this decay time allows tumours to be distinguished from healthy tissue with high sensitivity – and can even differentiate between different types of tumours: an invaluable advantage for surgeons!