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Thomas Callan, Sophie Kubach, Simon Antonio Bello, Warren Lewis, Nolleisha Graves, Mary Durbin, Roger A. Goldberg; Neighboring B-scan averaging for improved visualization of retinal substructures with SS-OCT. Invest. Ophthalmol. Vis. Sci. 2020;61(9):PB0024.
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Image quality is one of the most important factors when using optical coherence tomography (OCT) as a diagnostic tool. Speckle artifacts and signal-to-noise ratio (SNR) heavily influence the appearance of B-scans. This study analyzed the effectiveness of averaging neighboring B-scans for improving image quality and the visualization of retinal substructures in the B-scans from volume images.
Images were acquired from both healthy and diseased eyes with a prototype PLEX® Elite 9000 (ZEISS, Dublin, CA) swept-source OCT that acquired scans at both 100 kHz and 200 kHz scan speeds. A minimum of 25 scans were included from the following list of scan types: Angio 3x3 mm with a B-scan spacing (BSS) of 10 microns, 6x6 (BSS:12um), 9x9 (18), 12x12 (24), HD 12x12 (15) 15x9 (18) and Cube 1024x1024 (12), 800x800 (15) and 512x512 (24) structure scans.Two sets of scans were created. One set used the traditional processing for an individual B-scan. The second set was processed by averaging the primary B-scan with all neighbors acquired within 36um, Averages included either 3 or 2 B-scans. For grading, both the original and the neighbor-averaged B-scans were displayed side-by-side to an expert grader. A rating scale of 1-5 was used to assess the image quality comparison. A minimum of 6 B-scans were selected from each volume and compared between the two formats prior to determining a single grade for each comparison.
A total of 283 scans (49 healthy, 234 disease) were processed and the pairs compared and graded. At least 73% or more of the averaged-neighbor scans were preferred (grade 4 or 5) in all scan categories except for the HD Angio 12x12 mm (see Table 1). The remaining averaged neighbor B-scans were as good or better than the single scan but did not show the overwhelming preference as the other scans. The benefit from enhancing the B-scans is most pronounced for the Angio 6 x 6 mm ONH scans followed by the 1024x1024 mm cube scans.
Utilizing the neighboring B-scan was shown to improve most B-scans in this comparison study. There did not appear to be any detriment to visualizing small features with neighbor averaging. The averaged B-scan showed greater detail, less graininess, and improved clarity of the layers (see Figure 1).
This is a 2020 Imaging in the Eye Conference abstract.
Table 1: Comparison grades showing average scores and percentages
Figure 1 a-d: Two examples of the single B-scan (left) and neighbor B-scan averaging (right)
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