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Jeff Fingler, Aldo Arturo Oregon-Miranda, Srinivas R Sadda, Scott Fraser; Phase variance OCT angiography for three-dimensional vascular visualization in AMD. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4536.
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Phase variance optical coherence tomography (pvOCT) angiography is a novel data processing method which can visualize three-dimensional vasculature from the phase of repeated, sequential B-scans of OCT imaging data. The purpose of this study is to evaluate the capabilities of pvOCT to visualize vascular abnormalities within cases of age-related macular degeneration (AMD), while improving the technique for vascular screening.
Selected normal and AMD subjects were imaged with a variety of pvOCT scan patterns using a modified Zeiss Stratus OCT scan head, adapted to run at an acquisition rate of 80kHz. Using a range of scanning densities and imaging statistics, pvOCT angiography retinal imaging rates ranging from 2 x 2 mm2 to 8 x 10 mm2 with acquisition times of less than 5 seconds were performed and evaluated. The processing of the pvOCT data sets was varied for each set to optimize for vascular visualization and feature resolution while reducing extraneous phase noise contributions and artifacts. Multiple segmentations and visualizations of the three-dimensional pvOCT data were computed, to provide en face visualizations of retinal and choroidal vasculature at different depths for comparison with clinical fluorescein angiography.
Successful visualization of retinal and anterior choroidal vascular features was achieved for a wide range of scanning densities and imaging statistics chosen for the pvOCT scan patterns. Optimal scan patterns depended on the required resolution of vascular features, but in general vascular visualization was able to be maintained for scan sizes of 4x4 mm2 to 6x6 mm2. For the en face visualizations, anterior boundary segmentations were successfully used to view the retinal vasculature, the anterior choroidal vasculature, and possible instances of choroidal neovascularization (CNV).
Vascular imaging with pvOCT has the potential to be used for non-invasive screening for abnormal vasculature changes in the retina and choroid, such as the appearance of CNV in AMD. With the additional implementation of eye tracking and image registration, this technique can be applied to imaging vasculature over even wider fields of view than currently demonstrated.
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