Vessel Centripetality: A New Indicator for Morphological Analysis of Arteries And Veins

It is well known that arteries and veins play different roles in retina, and the retinal arteriolar-to-venular ratio may hint at some retinal diseases. Tortuosity of retinal vessels has been identified as one of earliest indicators to a number of vascular and nonvascular diseases. Therefore, it is essential for quantitative analysis of morphological differences between arteries and veins. Retinal arteries and veins have a clear tendency toward the center of foveal avascular zone (FAZ) during the extension process. In order to quantitatively describe this morphological feature, we propose a new indicator, vessel centripetality (VC), to distinguish retinal arteries and veins in optical coherence tomography angiography (OCTA) images. In order to reflect the centripetality, the arteries and veins are graded separately, mainly divided into first-level and second-level vessels. The experimental results on a manually annotated artery-to-vein (AV) dataset with 100 OCTA cubes demonstrate that VC is an effective indicator to describe the morphological differences of arteries and veins, and the utilization of global retinal vessel position information makes VC more stable than existed morphological indicators that only consider the local position information.