January 2015
Spotlight Summary by Robert J. Zawadzki
Adaptive optics optical coherence tomography at 1 MHz
Almost 25 years after the first demonstration of optical coherence tomography (OCT), it is clear that the image acquisition speed offered by this now mature technology is one of the main parameters defining its present and future usefulness in bio-medical and industrial applications. The current work presented by Kocaoglu, Turner, Liu and Miller focuses specifically on this aspect of OCT technology and explores in a very elegant way the acquisition speed limit achievable by state-of-the-art CMOS line-scan cameras. This type of detector is very common in several modern spectrometer-based Fd-OCT systems, making the results in this paper of wide interest across the OCT community.
To achieve 1MHz A-line acquisition rate (which is the fastest ophthalmic OCT system operating in the 700 to 915 nm spectral band) the authors used a novel detection channel design based on four high-speed spectrometers that receive light sequentially from a 1 × 4 optical switch assembly. This manner of control makes use of all available light in the detection channel and avoids camera dead time, both of which are critical for maintaining imaging system sensitivity. To demonstrate the benefits of such increase in acquisition speed, the authors applied it to a novel multi-camera adaptive optics (AO-) OCT system for ophthalmologic use operating at a wavelength of 790 nm, with 5.3 μm axial resolution in retinal tissue and light power incident on the subject’s cornea of only 430 μW. The application of AO allowed the utilization of a larger numerical aperture and therefore more efficient detection of backscattered light, yielding retinal images of comparable dynamic range to those of clinical OCT. The system’s performance was validated by a series of experiments that included imaging in both model and human eyes. The authors demonstrated the capability of this new MHz AO-OCT system for capturing detailed images of individual retinal nerve fiber bundles and cone photoreceptors.
I believe that increases in the acquisition speed of AO-OCT technology will help to reduce degrading effects of retinal movements present in AO-OCT volumetric data sets. This should result in increased usefulness of this modality for studying cellular-level volumetric retinal morphology in healthy and diseases retinas.
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To achieve 1MHz A-line acquisition rate (which is the fastest ophthalmic OCT system operating in the 700 to 915 nm spectral band) the authors used a novel detection channel design based on four high-speed spectrometers that receive light sequentially from a 1 × 4 optical switch assembly. This manner of control makes use of all available light in the detection channel and avoids camera dead time, both of which are critical for maintaining imaging system sensitivity. To demonstrate the benefits of such increase in acquisition speed, the authors applied it to a novel multi-camera adaptive optics (AO-) OCT system for ophthalmologic use operating at a wavelength of 790 nm, with 5.3 μm axial resolution in retinal tissue and light power incident on the subject’s cornea of only 430 μW. The application of AO allowed the utilization of a larger numerical aperture and therefore more efficient detection of backscattered light, yielding retinal images of comparable dynamic range to those of clinical OCT. The system’s performance was validated by a series of experiments that included imaging in both model and human eyes. The authors demonstrated the capability of this new MHz AO-OCT system for capturing detailed images of individual retinal nerve fiber bundles and cone photoreceptors.
I believe that increases in the acquisition speed of AO-OCT technology will help to reduce degrading effects of retinal movements present in AO-OCT volumetric data sets. This should result in increased usefulness of this modality for studying cellular-level volumetric retinal morphology in healthy and diseases retinas.
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Article Information
Adaptive optics optical coherence tomography at 1 MHz
Omer P. Kocaoglu, Timothy L. Turner, Zhuolin Liu, and Donald T. Miller
Biomed. Opt. Express 5(12) 4186-4200 (2014) View: Abstract | HTML | PDF