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Wei Chieh Huang, Ying Dong, Ben Turley, Robert Gibson, Charles A Reisman; Signal-to-Noise Ratio Comparisons Between Spectral-Domain and Swept-Source OCTs. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1318.
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© ARVO (1962-2015); The Authors (2016-present)
Swept-source (SS) OCT utilizing a laser with wavelength centered at 1050 nm has smaller sensitivity falloffs and deeper penetration compared to spectral domain (SD) OCT with light centered at 850 nm. SS-OCT can produce images with clearer structural details from vitreous to choroid simultaneously. This study demonstrated the image quality differences by comparing between SD- and SS-OCTs the signal-to-noise ratio (SNR) of different retinal layers.
60 eyes from 30 healthy volunteers (age ranged 23-67 years) were imaged by an SD-OCT and an SS-OCT (3D OCT1 Maestro and DRI OCT Triton, Topcon Corp, Japan). At least one high quality retinal image was captured per image mode, macula, disc, and wide, per machine. The machine-generated SNRs, expressed as TopQ scores, were estimations of the degree of overlap and distribution similarity between background (noise) and foreground (retina + choroid) signals. The OCT scans were also divided into different retinal regions and the SNRs were estimated similarly: SNRretina, where foreground consisted of the regions between inner limiting membrane to Bruch’s Membrane (BM), and SNRchoroid, whose foreground consisted of the regions from the BM to 350 mm scleral of BM. TopQ, SNRretina, and SNRchoroid were compared between the devices. Sensitivity falloffs were examined with SNRs from different retinal layers that were normalized to their overall TopQ score.
The average SD-OCT TopQ scores were 49.8 ± 5.1, 52.9 ± 4.5, 40.4 ± 5.6 for disc, macula, and wide scans respectively. The average SS-OCT TopQ were higher for all scan modes, at 62.3 ± 4.7, 66.8 ± 3.6, and 62.2 ± 4.1 (p < 0.001). Comparisons in different retinal regions showed higher SNRs in SS-OCT in all scan patterns (p<0.001). The average SD-OCT SNRretina were 49.3 ± 5.2, 54.6 ± 5.4, and 42.5 ± 6.7, whereas the average SS-OCT SNRretina were 63.7 ± 5.0, 67.8 ± 3.6, and 64.0 ± 4.4. The average SNRchoroid for SD-OCT were 16.8 ± 5.4, 18.7 ± 4.7, and 13.3 ± 3.7, whereas for SS-OCT the average SNRchoroid were 49.1 ± 4.6, 52.2 ± 6.2, 49.0 ± 5.5. Signal falloffs in choroid were 66 ± 9%, 64 ± 10%, and 67 ± 8% in SD-OCT, which were greater than in SS-OCT, 23 ± 8%, 21 ± 10%, and 21 ± 8% (p<0.001).
Overall there were higher SNRs in SS-OCT images. SS-OCT provided images with a deeper imaging depth and clearer lamination of the choroid without losing signal in the vitreous.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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