OCT angiography with optimized numerical k-sampling

Abstract

Purpose : This study aims to achieve high-quality structural imaging and angiography using a 200-kHz Optical Coherence Tomography Angiography (OCTA) device by addressing the challenges associated with k-clock instability.

Methods : Healthy eyes were imaged with a custom-built OCTA system incorporating optimized numerical k-sampling. The system utilized a laser with a central wavelength of 1050 nm, a tunable range of 100 nm, and a rapid 200-kHz sweep rate, enabling a lateral optical resolution of 19 µm and an axial resolution of 6.2 µm in tissue. To eliminate the need for expensive external k-clocks and high-speed digitizers, a numerical k-sampling algorithm guided by sidelobe suppression value was proposed, extending imaging depth while maintaining a balance between resolution and sensitivity (5 dB roll-off at 6 mm). A high signal-to-noise ratio for flow signal was achieved through split-spectrum amplitude-decorrelation angiography (SSADA). A median subtraction algorithm minimized bulk motion artifacts. We removed projection artifacts in the deep capillary plexus (DCP) using slab subtraction with the superficial vascular complex (SVC). A single scan was completed within 4 seconds to minimize eye fatigue. Image segmentation utilized COOLART software.

Results : A healthy volunteer was imaged. Cross-sectional OCT images of the macular region revealing the optimized numerical k-sampling could efficiently improve the resolution. En face DCP and SVC angiograms further demonstrated the effectiveness of our methodology.

Conclusions : Our study demonstrates that a 200-kHz OCTA device employing optimized numerical k-sampling enables high-quality structural OCT and capillary-scale OCTA imaging without external k-clock.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.