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Toshiaki Nakagawa, Yoshitsugu Matsui, Masaharu Mizuochi, Mineo Kondo; A simple estimation method for visualization quality in retinal OCT images. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4780.
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© ARVO (1962-2015); The Authors (2016-present)
To describe a simple estimation method for visualization quality in retinal optical coherence tomography (OCT) images and to evaluate the validity in the three hyperreflective outer retinal bands seen in ultrahigh-resolution spectral-domain OCT.
In our proposed method, the visualization quality of the external limiting membrane (ELM), the inner segment/outer segment (IS/OS) junction, and the cone outer segment tips (COST) line was evaluated based on intensity profile obtained through an OCT image along the depth axis. The profile was taken from a rectangle area around the three bands with median filtering along the x-axis. The visualization quality of the band was estimated by peak height score (PHS) defined as the ratio of peak height to peak tail. PHS was standardized with display grayscale ranging from 0.0 to 1.0. The estimation method was used to a prototype OCT system with an axial resolution of 2 μm and an imaging speed of 37,000 single axial scans (A-scans) per second. A comparison of PHS was performed on OCT images obtained under three types of the number of B-scans for image averaging: 10, 50, and 100 B-scans, and two types of averaging technique based on area pattern matching algorithm (averaging algorithm 1: AA1) and line-divided pattern matching algorithm (averaging algorithm 2: AA2 ).
PHS obtained on OCT images averaged from 10, 50, and 100 B-scans using AA1 were 0.42, 0.34, 0.27 for ELM, 0.25, 0.21, 0.16 for IS/OS, and 0.2, 0.15, 0.09 for COST, and those obtained using AA2 were 0.42, 0.42, 0.39 for ELM, 0.25, 0.3, 0.26 for IS/OS, and 0.19, 0.18, 0.15 for COST, respectively. PHS varied depending on the number of B-scans used for image averaging and averaging algorithm. It was tended PHS became lower when the number of B-scans used for image averaging was increased and PHS of AA2 was higher than that of AA2.
PHS may assist in estimation procedure for visualization quality of the three hyperreflective outer retinal bands in retinal OCT images.
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