Abstract
Purpose :
The usefulness of optical coherence tomography angiography (OCTA) in clinical practice is heavily influenced by the scan resolution. Angio 3x3 mm scans provide best commercially available scan resolution, however, due to its limited field of view (FOV), it is commonly complemented with an Angio 6x6 mm scan with a lower resolution. In this study we compare the image quality of a traditional Angio 3x3 mm scan with a High Definition (HD) 6x6 mm Angio scan.
Methods :
A modified PLEX® Elite 9000 (ZEISS, Dublin, CA) was used to image 10 subjects (5 healthy and 5 diseased eyes) with the following protocol:
Pattern 1: 3x3 mm FOV consisting of 300 A-lines/B-scan and 300 B-scans acquired at 100kHz with 4 repetitions for angiography processing.
Pattern 2: 6x6 mm FOV consisting of 600 A-lines/B-scan and 600 B-scans acquired at 200kHz with 3 repetitions for angiography processing. HD 6x6 mm OCTA volumes are generated by processing clusters of three B-scan repetitions each for a shorter acquisition time, and the processing algorithm has been modified to enhance sensitivity to lower blood flow velocity.
An experienced grader compared quality and details of two scan patterns by grading the en-face slabs on a scale of 1-5 in a blind study. 6x6 mm images for every subject were cropped to a 3x3 mm FOV before comparison.
Results :
As expected from the fact that the same sampling resolution was used in both patterns, HD 6x6 mm en-face views of the retinal slabs reveal comparable details and similar quality as seen in 3x3 mm scans (Figure 1). However, HD 6x6 mm scans also provide a larger FOV (Figure 1c), which is often necessary to visualize the extent of vascular lesions, for example in patients with macular neovascularization (MNV). Figure 2 shows the outer retina to choriocapillaris (ORCC) slab. Although both patterns provide the same resolution, the extent of MNV is only fully captured in the HD 6x6 mm en face projection.
Conclusions :
We demonstrated that HD 6x6 mm scans provide a larger FOV while maintaining the same quality and detail as Angio 3x3 mm scans, and thus might be a suitable replacement for the Angio 3x3 mm scan in clinical practice.
This is a 2021 ARVO Annual Meeting abstract.