High-speed Optical Coherence Tomography System Research Articles

Three-dimensional Imaging of Macular Holes with High-speed Optical Coherence Tomography

To demonstrate the advantages of 3-dimensional imaging of macular hole pathology using new-generation high-speed optical coherence tomography (OCT). Prospective observational case series. Twenty-one eyes from 20 consecutive patients diagnosed with a macular hole. A prototype high-speed OCT system was built based on a Fourier-domain OCT (FD OCT) technology for patient examination. The system has achieved sensitivity of approximately 98 decibels, axial resolution of approximately 4.3 mum in tissue, and an acquisition rate of approximately 18,700 axial scans per second. Three-dimensional imaging of macular hole pathology was performed based on a raster scan protocol consisting of 256x256 axial scans. All patients were imaged with 3-dimensional OCT, Stratus OCT, and OCT Ophthalmoscope C7. Images of macular hole pathologies obtained by 3-dimensional OCT and standard OCT instruments. The 3-dimensional OCT imaging successfully generated realistic 3-dimensional images of the vitreofoveal interface and intraretinal microstructures associated with a macular hole. The 3-dimensional overview of the vitreofoveal interface was helpful in gaining an immediate understanding of the dynamic interactions of the vitreous and fovea. Observations of consecutive en face images in combination with conventional longitudinal images and of cross-sectional images in combination with sectioned volume images enabled identification of intraretinal microstructures and their 3-dimensional extension associated with a macular hole, such as subfoveal structural changes after vitreous traction, connection of the flap to intraretinal structures, the external limiting membrane (ELM) and its disruption, and elevated photoreceptor inner and outer segments delineated by the ELM. The appearance of inner-wall images of a macular hole produced by photoreceptor inner and outer segment backreflection varied throughout macular hole stages. Three-dimensional imaging of macular holes with high-speed OCT based on FD OCT technology offers 3-dimensional overviews that facilitate understanding of the abnormalities in the vitreofoveal interface. It also provides consecutive orthogonal images that allow much more precise and minute observation of 3-dimensionally extending intraretinal structural changes associated with a macular hole than conventional OCT imaging, especially in the photoreceptor inner and outer segments.

Clinical Application of Rapid Serial Fourier-Domain Optical Coherence Tomography for Macular Imaging

To introduce and examine the utility of a retinal imaging technique using high-speed optical coherence tomography (OCT) for creating a more complete retinal structural map to aid in the evaluation of patients with macular pathology. Prospective observational case series. Five patients with a variety of macular pathologies. Patients were imaged with a Fourier-domain high-speed high-resolution OCT system built at our institution. A sweeping serial OCT B-scan of the macula was acquired to create a detailed retinal structural map. The data were then used to make individual clinical observations. Rapid serial OCT B-scans produced detailed macular maps for all 5 patients. Diagnoses of imaged patients included macular hole, lamellar macular hole, regressed macular hole or macular microhole, choroidal neovascular membrane (CNV) from age-related macular degeneration, and CNV from presumed ocular histoplasmosis syndrome. Reconstructed B-scans and C-scans are shown for selected patients to illustrate the additional perspectives gained by obtaining a detailed retinal map. Rapid serial Fourier-domain OCT B-scanning can be used to create a detailed retinal structural map. This technique provides additional information that can be missed on single OCT images and provides an accurate way to image large or complex lesions, and allows B-scan and C-scan reconstructions to be made that provide additional perspectives into retinal structures that may be missed using traditional imaging methods.

Dynamic focus control in high-speed optical coherence tomography based on a microelectromechanical mirror

In high-resolution optical coherence tomography (OCT), a high numerical aperture sample lens is required to achieve high lateral resolution. This situation leads to a limited depth of focus, which can yield sub-optimal lateral resolution outside the focal zone for deep-imaging OCT systems. To maintain high transverse resolution over the entire depth scan, we designed a high-speed dynamic focus control system based on a microelectromechanical mirror. The silicon nitride deformable mirror shifted the focus of the sample beam of the OCT interferometer in synchrony with the coherence-gate scan in the reference arm. As a result, the coherence gate remained at the beam focus during the whole imaging process. The prototype focus control setup was integrated into a high-speed (8 kHz depth scan frequency) OCT system. Improvement to the image quality was demonstrated with a standard resolution target.

Rapid acquisition of in vivo biological images by use of optical coherence tomography

The development of techniques for high-speed image acquisition in optical coherence tomography (OCT) systems is essential for suppressing motion artifacts when one is imaging living systems. We describe a new OCT system for performing micrometer-scale, cross-sectional optical imaging at four images/s. To achieve OCT image-acquisition times of less than 1 s, we use a piezoelectric fiber stretcher to vary the reference arm delay. A Kerr-lens mode-locked chromium-doped forsterite laser is employed as the low-coherence source for the highspeed OCT system. Dynamic, motion-artifact-free in vivo imaging of a beating Xenopus laevis (African frog) heart is demonstrated.