In vivo rotational three-dimensional OCTA analysis of microaneurysms in the human diabetic retina

Abstract

The aim of this study was to explore whether rotational three-dimensional (3D) visualization of optical coherence tomography angiography (OCTA) volume data may yield valuable information regarding diabetic retinal microaneurysm (MA) characteristics. In this retrospective, observational study, we collected data from 20 patients (20 eyes) with diabetic retinopathy. Subjects were imaged with the SS-OCTA system (PLEX Elite 9000, Carl Zeiss Meditec Inc., Dublin, CA, USA). The OCTA volume data were processed with a volume projection removal algorithm and then exported to imageJ in order to obtain a 3D visualization of the analyzed MAs. The rotational three-dimensional OCTA images were qualitatively and quantitatively investigated. A total of 52 MAs were included in the analysis. On rotational 3D OCTA images, the number of vessels associated with each MA varied between 1 and 4, and most MAs (59.6%) were associated with 2 vessels. Moreover, in 20 MAs (38.4%) these vessels seem to originate from the SCP, while 26 MAs (50.0%) had associated vessels originating from the DVC, and 6 MAs had associated vessels arising from both the SCP and DVC (11.6%). Most MAs (31/52) had a ‘saccular’ shape. The number of retinal layers occupied by each MA ranged between 1 and 3 and the inner nuclear layer was the retinal layer most frequently occupied by MAs. In conclusion, this study used an algorithm to obtain rotational three-dimensional visualization of retinal MAs. The MAs’ architecture is complex and 3D visualization may clarify the true vascular origin of these lesions, which is often mistaken using en face OCTA images.

Quantification of diabetic macular ischemia using novel three‐dimensional optical coherence tomography angiography metrics

“…A previously semi-automated and validated algorithm was employed to obtain 3D visualization of OCTA data [22,25]. To mitigate the influence of projection artifacts, we used a volume projection removal algorithm which was described in our previously published studies [22,25].…”

“…A previously semi-automated and validated algorithm was employed to obtain 3D visualization of OCTA data [22,25]. To mitigate the influence of projection artifacts, we used a volume projection removal algorithm which was described in our previously published studies [22,25]. Successively, the obtained corrected OCTA volume scans were exported as uncompressed 8-bit raw-data file and imported into Fiji distribution of ImageJ (software version 2.0.0, National Institutes of Health, Bethesda, MD; available at http://rsb.info.nih.gov/ij/ index.html) [29] and re-oriented in space so that the first dimension corresponded to the axial direction with increased pixel number as increasing depth, and the second and third dimensions corresponded to the horizontal and vertical directions, respectively [22,25].…”

“…This may have important consequences eventually resulting in an underestimation of the flow: (a) overlapping vessels in the same slab may appear as merged; and (b) vessels crossing multiple retinal layers and connecting different vascular beds may not be detected [6]. In addition, the 2D en face visualization may also overestimate perfusion in cases where retinal vessels or vascular abnormalities (eg, microaneurysms) cross two consecutive slabs and are thus visualized twice (on two different en face images) [22,23]. Finally, en face images may be altered because of segmentation errors which may limit their utility, especially in pathological tissue [6,24].…”

“…Finally, en face images may be altered because of segmentation errors which may limit their utility, especially in pathological tissue [6,24]. Conversely, a 3D illustration does not require flattening of flow data and also permits rotation of the vessels on the three axes which further reduces limitations by vessel foreshortening and overlapping anatomy [22,25]. 3D visualization has proven to be beneficial in different macular affections, including macular edema due to retinal vascular disturbances [26], type 3 macular neovascularization associated with age-related macular degeneration [25], and DR [22].…”

“…Conversely, a 3D illustration does not require flattening of flow data and also permits rotation of the vessels on the three axes which further reduces limitations by vessel foreshortening and overlapping anatomy [22,25]. 3D visualization has proven to be beneficial in different macular affections, including macular edema due to retinal vascular disturbances [26], type 3 macular neovascularization associated with age-related macular degeneration [25], and DR [22]. However, although these studies provided an accurate description of 3D visualization in these disorders, they failed to provide quantitative metrics.…”