Abstract
Purpose :
3D image analysis may be beneficial to analyze a detail of the choroidal vasculature. Although a whole vascualar structure must be delineated for this purpose, commercially aveilable OCT angiography could not detect a whole choloidal vessel. OCT angiography provide two types of the vessel images in the choroid, i.e. heigh intensity flow information in OCT angiography (OCT-A) and silhouette images of the large vessels in stractural OCT (OCT-S). We attempted to make hybrid 3D models of the choroidal vessel from two different types of vessel images and examined the characteristics of the 3D models.
Methods :
Design: Prospective observational case series. Subjects:20 eyes of 20 healthy individuals The images were taken by using swept source (SS)-OCT (Elite 9000, Zeiss, Carl Zeiss Meditec, Dublin, California, USA). 6 x 6 mm square images of OCT-S and OCT-A were exported separately as stack images. A OCT-S image stack was inverted to white vessel images to black background. Vessel images of OCT-A and inverted OCT-S were segmented and visualized three dimensionally by using open-source software 3D slicer, which was an open-source software platform for biomedical research (ver. 4.10; https://www.slicer.org/). Vessel volume of the choroid was measured. Similarity of segmented choroidal vessel between OCT-S and OCT-A was calculated.
Results :
The ages of the subject was 28 ± 4.3 (mean ± SD). The axial length was 24.6 ± 1.0 mm.The choroidal vessel was successfully segmented and visualized three dimensionally in all eyes. The vessels visualized from OCT-A arranged surround a large choroidal vessels visualized from OCT-S. Total volume of the choroidal vessel at the fovea the choroid was 3.01 mm3, which decreased with the axial length.The vessel ratio to the volume of the choroidal tissue was 40%. Of the total vessel volume, 73% were vessels visualized from OCT-S and 27% were vessels visualized from OCT-A. The mean of Dice similarity coefficient between the vessel volume from OCT-S and OCT-A was low (0.05 ± 0.02).
Conclusions :
More than 40% of the choroidal tissues at the fovea may be composed of blood vessels in the hybrid 3Dmodel in healthy subjects.The choroidal vessel volume calculated from the silhouette image of OCT-S may be 27% or more less than the actual vessel volume.
This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.