Fig 1.
Retinal image quality criteria (3x3-mm angiograms) in the superficial capillary plexus (SCP) and deep capillary complex (DCC).
A.B. Vessel sharpness, SCP (A: 0 = poor; B: 2 = good); C.D. FAZ visibility, SCP (C: 0 = poor; D: 2 = good); E.F. Artery-vein distinction, SCP (E: 0 = poor; F: 2 = good); G.H. Vortex visibility, DCC (G: poor; H: 2 = good); I.J. Peripheral image quality, SCP (I: poor; J: 2 = good); K.L. Segmentation errors, DCC (K: poor; L: 2 = good); M.N. Background noise, SCP (M: poor; N: 2 = good); O.P. Motion artifacts, SCP (G: poor; H: 2 = good). The orange arrow on image O is showing the discontinuity of vessel course (motion artifact).
Fig 2.
Choriocapillaris image quality assessment (3x3-mm angiograms).
The overall image quality seems greater in B compared to A with higher uniformity and capillary sharpness, and fewer artifacts (for example, one projection artifact is showed by the white circle) (A: medium overall image quality; B: good overall image quality). The visualization of flow voids is enhanced in D compared to C with a better contrast in flow and no-flow areas (C: medium visualization of flow voids; D: good visualization of flow voids).
Fig 3.
Comparison of quantitative measurements in 3x3-mm angiograms (A, B, C, D) and 2.25x2.25-mm angiograms (D, F, G, H). A and E: Superficial capillary plexus angiograms. B and F: Perfusion trace allowing measuring perfusion density, and showing the inner ring used to compare the measurements. This inner ring is delimited by a 2-mm diameter circle, and a 1-mm diameter circle (in red). C and G: Vessel trace allowing measuring perfusion density. D and H: The foveal avascular zone is delineated in red.
Fig 4.
Comparison between 3x3-mm standard angiograms (A, D), the same 3x3 mm angiograms cropped to a 2.25x2.25 mm field of view (B, E) and 2.25x2.25-mm angiograms (C, F) acquired with the Beam Expander (BE). A, B and C: Superficial capillary plexus; D, E and F: Deep capillary complex (DCC). The vessels are more continuous (as circled on the images A, B and C) in the BE scans, resulting in a higher uniformity of image quality. Some vessels are more visible (white arrow), contributing to improve the visualization of the foveal avascular zone. The radial organization of the vortex in the DCC is better defined in F than in E (white asterisk).
Table 1.
Comparison of the qualitative criteria used for the single scans acquired with and without the beam expander (BE) module.
Table 2.
Comparison of the qualitative criteria used for the average scans acquired with and without the beam expander (BE) module.
Fig 5.
Comparison of choriocapillaris images from the same healthy subject.
A. 3x3-mm standard angiogram. B. Same 3x3-mm angiogram cropped to match the scan area of the corresponding 2.25x2.25-mm angiogram. C. 2.25x2.25-mm angiogram acquired with the Beam Expander and registered using the superficial slab of the to the 3x3 mm angiogram for comparison. The flow voids are more distinct in C and the capillary structures are better defined.
Table 3.
Comparison of the quantitative criteria used for the single whole retina scans acquired with and without the beam expander (BE) module.
Fig 6.
Comparison between single (A, C, E) and average (B, D, E) 2.25x2.25-mm angiograms (performed with Beam Expander). A and B: Superficial capillary plexus (SCP); C and D: Deep capillary complex; E and F: Choriocapillaris.
Table 4.
Qualitative criteria: comparison between single BE and averaged 3x3 mm scans.
Table 5.
Comparison of the quantitative criteria used for the single superficial scans acquired with and without the Beam Expander (BE) module.