title: Angiography of the retina and the choroid with phase-resolved OCT using interval-optimized backstitched B-scans.
abstract: In conventional phase-resolved OCT blood flow is detected from phase changes between successive A-scans. Especially in high-speed OCT systems this results in a short evaluation time interval. This method is therefore often unable to visualize complete vascular networks since low flow velocities cause insufficient phase changes. This problem was solved by comparing B-scans instead of successive A-scans to enlarge the time interval. In this paper a detailed phase-noise analysis of our OCT system is presented in order to calculate the optimal time intervals for visualization of the vasculature of the human retina and choroid. High-resolution images of the vasculature of a healthy volunteer taken with various time intervals are presented to confirm this analysis. The imaging was performed with a backstitched B-scan in which pairs of small repeated B-scans are stitched together to independently control the time interval and the imaged lateral field size. A time interval of ≥ 2.5 ms was found effective to image the retinal vasculature down to the capillary level. The higher flow velocities of the choroid allowed a time interval of 0.64 ms to reveal its dense vasculature. Finally we analyzed depth-resolved histograms of volumetric phase-difference data to assess changes in amount of blood flow with depth. This analysis indicated different flow regimes in the retina and the choroid.
authors.affiliation: Rotterdam Ophthalmic Institute, Schiedamse Vest 160, 3011 BH Rotterdam, The Netherlands. b.braaf@eyehospital.nl
authors.forename: Boy
authors.initials: B
authors.lastname: Braaf
authors.forename: Koenraad A
authors.initials: KA
authors.lastname: Vermeer
authors.forename: Kari V
authors.initials: KV
authors.lastname: Vienola
authors.forename: Johannes F
authors.initials: JF
authors.lastname: de Boer
mesh_terms: D000465:Algorithms; D000792:Angiography / Q000295:instrumentation*; D019842:Ciliary Arteries / Q000033:anatomy & histology*; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods*; D015203:Reproducibility of Results; D012171:Retinal Vessels / Q000033:anatomy & histology*; D042261:Retinoscopes; D012680:Sensitivity and Specificity; D041623:Tomography, Optical Coherence / Q000295:instrumentation*