Projection-resolved optical coherence tomographic angiography

Abstract

Shadowgraphic projection artifacts from superficial vasculature interfere with the visualization of deeper vascular networks in optical coherence tomography angiography (OCT-A). We developed a novel algorithm to remove this artifact by resolving the ambiguity between in situ and projected flow signals. The algorithm identifies voxels with in situ flow as those where intensity-normalized decorrelation values are higher than all shallower voxels in the same axial scan line. This "projection-resolved" (PR) algorithm effectively suppressed the projection artifact on both en face and cross-sectional angiograms and enhanced depth resolution of vascular networks. In the human macula, the enhanced angiograms show three distinct vascular plexuses in the inner retina and no vessels in the outer retina. We demonstrate that PR OCT-A cleanly removes flow projection from the normally avascular outer retinal slab while preserving the density and continuity of the intermediate and deep retinal capillary plexuses.

Visualization of micro-capillaries using optical coherence tomography angiography with and without adaptive optics

“…However, using OCTA these studies are limited to the evaluation of the integrative vessel pattern consisting of several vessel beds which is not ideal. This problem can be reduced by using algorithms that remove projections artifacts [47]. A comparison with such algorithms and AO-OCTA on the retina is still missing and could be further investigated.…”

Angiographic and structural imaging using high axial resolution fiber-based visible-light OCT

“…Although four retinal capillary plexuses in human retina have been reported [52], a projection-resolved algorithm [51,53] has to be applied. By using vis-OCT, projection artifacts of superficial capillary flow were not discerned in the deeper plexuses, presumably because of the combination of stronger reflectance in capillaries located at deeper layers and larger attenuation of the projected superficial flow at visible light wavelengths.…”

“…3(C)). Inspection of the angiographic z-profile showed three distinct retinal plexuses: superficial vascular plexus (SVP), intermediate capillary plexus (ICP) and deep capillary plexus (DCP), resembling the axial vascular distribution of the human retina [51][52][53] and mouse retina [54]. Below Bruch's membrane, the flow signal from the choriocapillaris was detected.…”

Diabeteses kisér-károsodás vizsgálata optikai koherencia tomográfián alapuló angiográfiával

“…Ugyanakkor az OCT-angiográfia nem alkalmas az erekből történő folyadékszivárgás vizualizálására, és jelenleg nem képes a perifériás retinaterületek leképezésére sem [37]. Jelen tanulmányunkban a macula területén a felszíni kapillárisér-hálózat sűrűségét elemeztük, miután a mély kapillárisér-hálózat sűrűségének vizsgálata jelenleg még nem kellően megbízható a projekciós műtermé-kek miatt [38,39].…”