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13 Jun 2016
Combination of silicon photonics and III-V laser source in coin-sized system could even end up on supermarket shelves, suggests principal investigator.
Advances in silicon photonics development for datacom applications are set to be applied in biophotonics, with a new €4.9 million European project aiming to create a tiny and low-cost system for optical coherence tomography (OCT).
While OCT has become widely used for ophthalmic diagnosis and is gaining traction in cardiovascular imaging, the technique still relies on relatively expensive and bulky combinations of laser, optical and electronic equipment.
Now a team led by Wolfgang Drexler from the Medical University of Vienna is aiming to shrink the core technology to no more than the size of a coin, primarily to diagnose eye diseases including diabetic retinopathy and glaucoma.
Industry collaboration
Officially the “OCTCHIP” (short for ophthalmic OCT on a chip) project began at the start of the year, and runs through the end of 2019 as part of the Photonics21-co-ordinated public-private partnership (PPP) funding scheme under Horizon 2020. Drexler and colleagues are aiming to have an initial prototype ready by the end of next year, and believe that mass production could be achieved by 2020.
Partnering the Vienna research team on the project are industry collaborators in the form of major player and medical imaging giant Carl Zeiss, Austrian sensor firm AMS, and the Swiss company Exalos, which has previously developed compact OCT “engines” based around a wavelength-swept source.
Other project contributors include University College Cork in Ireland, the Austrian Institute of Technology, and the Fraunhofer network in Germany.
According to the official abstract describing the four-year project, the plan is to exploit recent advances in silicon photonics and CMOS electronics for a healthcare application that is expected to grow in significance as the global population ages and diabetes becomes more prevalent.
The key difference compared with datacoms applications is that in biophotonics a visible-range light source is typically required and most silicon-on-insulator (SOI) waveguides are not compatible with wavelengths shorter than 1.1 µm.
“To this end, a novel CMOS-compatible, low-loss silicon nitride waveguide based [on a] photonic integrated circuit (PIC) technology platform will be developed in OCTCHIP and directly applied in the field of OCT for ophthalmology,” states the team, adding:
“The PIC technology developed in OCTCHIP will make a new generation of OCT systems possible with step-changes in size and cost beyond state-of-the-art. The monolithic integration of silicon nitride optical waveguides, silicon photodiodes and electronics combined with the hybrid integration of a III-V laser source will enable a compact, low-cost and maintenance-free solution.”
Supermarket OCT?
Drexler himself even envisages a time in the future when the ultra-compact technology could feature on supermarket shelves and be purchased by consumers for self-diagnosis.
“State-of-the-art OCT technology has its limitations: it is bulky, the size of a desktop and quite expensive, costing anything in the region of €100,000 per unit,” he said in an announcement about the project from Photonics21. “It can detect abnormalities but at the present moment, compact, cost-effective versions that can be used outside of hospitals and in private practice in a hand-held mode do not exist.”
However, with diabetic retinopathy now thought to be the cause of 200 million cases of blindness worldwide, including 60 million people in Europe, there is a clear case for a lower-cost, point-of-care diagnostic platform.
That said, the retina is an extremely complex part of the body, composed of more than ten layers of tissue despite being only 0.25 mm thick, and is very difficult to access.
Drexler said that the core component under development via the project will be no larger than the size of a 1 cent coin. “It will reduce costs and is maintenance-free,” he added. “OCTCHIP fosters widespread use to visualize and quantify the retina in more definition, so we can diagnose diseases better, quicker, and cheaper.”
The researcher even thinks that the core technology may extend to use in battery-powered capsules that patients could swallow for gastrointestinal diagnosis.
“Perhaps in the future this will be available in supermarkets, for self-diagnosis" he said.
Meanwhile, the start-up company Compact Imaging - which is based in California but has strong connections with researchers in Ireland - is developing similarly compact multiple-reference (MR) OCT and envisages commercializing a DVD drive-sized system.
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