"The value proposition for ophthalmic OCT is really clear – it's the only way to see the interior of the retina in a non-destructive and non-contact fashion," Eric Buckland, Bioptigen's president and CEO, told medicalphysicsweb. "The market for ophthalmic OCT is fairly well developed, but it's still growing."
This continued growth is due, at least in part, to the recent hike in performance enabled by the development of Fourier-domain OCT. First-generation technology – time-domain OCT – used a moving-mirror-based interferometer to generate images. But imaging in this manner will always be limited by the speed at which the mirror can be moved.
"We have adopted a Fourier-domain technique that has no moving parts in the interferometer," Buckland explained. "We acquire the signal in the wavelength space and Fourier-transform it to get the spatial information." Bioptigen's OCT system is based on the spectral-domain variety of this Fourier technology, in which a broadband source is employed and the entire signal (at all wavelengths) is recorded in parallel by a spectrometer.
The spectral-domain approach offers a signal-to-noise-ratio advantage of around 20 dB over time-domain OCT. That advantage translates into significantly faster imaging speeds. Bioptigen claims that its OCT system delivers non-invasive 3D imaging of the retina and cornea 50 times as fast asprevious technologies. The instrument, which uses a wavelength band centred on 840 nm, boasts an axial resolution of less than 6 μm and an imaging speed of 20 frames per second.
This high-speed imaging is essential when examining living subjects. "Previously, it could take a second or more to capture one frame of an image, so that required the use of image registration to remove motion artefacts," Buckland explained. "Our system captures 20 frames per second, so we freeze out artefacts of motion on a frame-wise basis. It also increases the resolution of the image by minimizing low-level blurring."
Timely approach
Buckland admits that Bioptigen, a spin-off from Duke University in Durham (NC), was not the very first to receive FDA approval for a spectral-domain OCT system, but he says that it was received "within 60 days of the first approval" following a race between several companies. He notes that Bioptigen has a slightly different approach to many others in the market, targeting research applications rather than diagnostics.
Bioptigen's OCT systems are designed to support advanced research in eye disease, including glaucoma, macular degeneration and diabetic retinopathy. The systems are offered with multiple scanning interfaces for in vivo imaging in humans and animals, as well as ex vivo tissue imaging.
"Our focus is on maximizing the image quality and also on subject flexibility," Buckland explained. "We have systems with a variety of scanning interfaces, as well as hand-held probes that provide extra versatility and a microscopy system for ex vivo use."
Furthering the progress of its OCT technology, Bioptigen has just been awarded two Phase II SBIR grants from the US National Institutes of Health. The first award is specifically to support development of an advanced retinal-imaging system and the company plans to use the cash to enhance two key areas of its device.
"Because our system uses a Fourier-domain approach, it's very heavy in signal processing, so we are advancing the signal processing to optimize real-time image processing and associated measurements," said Buckland. "We are also building scanning systems that optimize the non-standard applications."
He continued: "We are really pushing the signal processing, not just to create images but to extract information and do it in real time. Our competitors are focusing on the image-acquisition speed advantage as the number-one selling point. But in our view there is so much more. We can use this information to analyse ophthalmic disease at its earliest stage, not just as a diagnostic tool for symptomatic patients."
Ophthalmology accounts for about half of Bioptigen's OCT business. "It's not clear what else will offer long-term growth potential, but we are seeing tremendous pull across a variety of applications, from oncology to orthopaedics to vascular disease, and even dentistry, dermatology and tissue engineering," added Buckland.
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