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Yashila Marie Permeswaran, Jui-Kai Wang, Randy H Kardon, Mona Garvin; An En-Face OCT Registration Approach for Locating the Center of Bruch’s Membrane Opening in Longitudinal Papilledema Cases. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3593.
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© ARVO (1962-2015); The Authors (2016-present)
In cases of papilledema, the exact center of Bruch’s membrane opening (BMO) in an optical coherence tomography (OCT) volume can be difficult to locate due to obscuration from optic disc swelling. However, in longitudinal datasets, OCT volumes from future timepoints are often available with clearer BMO visibility due to the resolution of swelling. In this study, we propose an automated method to detect the BMO center (and corresponding central B-scan) in severe swelling cases using corresponding longitudinal OCT volumes with less swelling.
An OCT en-face image of the retinal pigment epithelium (RPE) complex was created for each subject at baseline and 6 months in the OCT substudy of the Idiopathic Intracranial Hypertension Treatment Trial (IIHTT). Meanwhile, the BMO contour in each RPE en-face image was segmented by a graph-based algorithm (Wang et al., SPIE 2015), and the BMO center was also estimated (Fig. 1A/1B). To register these longitudinal OCT en-face pairs, an approach similar to previous multimodal registration works was used (Miri et al., BOE, 2016). Potential landmark points in both RPE en-face images were automatically identified and paired based on calculated feature descriptors for each point (Fig. 1C), and the en-face images registered together based on these points (Fig. 1D). Following registration, the estimated BMO center in the 6-month en-face image was projected to the baseline en-face image (Fig. 1E). In addition, the central B-scan was determined in each image based on the y-location of the estimated center.
Of the 126 subjects, 78 had baseline and 6-month OCT scans for the study eye. The average distance from the initial baseline center to the 6-month center transformed back to the baseline en-face image was 189.3 microns, with the maximum distance reaching 576.0 microns. The new central B-scans (Fig. 2C) determined from the transformed centers were an average of 136.1 microns (4.5 slices) from the initial baseline central B-scans (Fig. 2A). Qualitative differences in these B-scans can be seen in Fig. 2.
Registration of 6-month OCT scans to their baseline counterparts leads to better alignment of central scans. Future work will explore using this registration for better BMO segmentation in severely swollen cases.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Steps of automated en-face registration and center transfer
Central B-scans based on respective centers
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