Swept Source OCT Angiography in Different Diseases

Swept source optical coherence tomography angiography (SS-OCTA) devices are the latest OCT technology to become commercially available. These units feature scan rates of 100,000 A-scans per second. In this chapter, the use of an ultra-high speed SS-OCTA prototype device developed at Massachusetts Institute of Technology (Cambridge, MA, USA) and deployed to New England Eye Center, Boston, MA will be discussed. The prototype SS-OCT system has been described previously, so only key attributes are considered for the purposes of this chapter [1]. This device utilizes a vertical-cavity surface-emitting laser (VCSEL) with a light source operating at a 1050 nm wavelength and a scan rate of 400,000 A-scans per second. Images are obtained by acquiring five repeated B-scans from 500 sequentially uniformly spaced locations on the retina, with each B-scan consisting of 500 A-scans. Thus a total of 5 × 500 × 500 A-scans are acquired per SS-OCTA volume with a total acquisition time of approximately 3.8 s. The imaging range is approximately 2.1 mm in tissue, and the axial and transverse resolutions in tissue are approximately 8–9 μm and approximately 15 μm, respectively. A post-processing registration step merges the orthogonally scanned “X-fast” and “Y-fast” volumes to patient motion artifacts [2].