Abstract
PurposeTo investigate the effect of B-spline-based elastic image registration on adaptive optics scanning laser ophthalmoscopy (AO-SLO)-assisted capillary visualization.MethodsAO-SLO videos were acquired from parafoveal areas in the eyes of healthy subjects and patients with various diseases. After nonlinear image registration, the image quality of capillary images constructed from AO-SLO videos using motion contrast enhancement was compared before and after B-spline-based elastic (nonlinear) image registration performed using ImageJ. For objective comparison of image quality, contrast-to-noise ratios (CNRS) for vessel images were calculated. For subjective comparison, experienced ophthalmologists ranked images on a 5-point scale.ResultsAll AO-SLO videos were successfully stabilized by elastic image registration. CNR was significantly higher in capillary images stabilized by elastic image registration than in those stabilized without registration. The average ratio of CNR in images with elastic image registration to CNR in images without elastic image registration was 2.10 ± 1.73, with no significant difference in the ratio between patients and healthy subjects. Improvement of image quality was also supported by expert comparison.ConclusionsUse of B-spline-based elastic image registration in AO-SLO-assisted capillary visualization was effective for enhancing image quality both objectively and subjectively.
Highlights
Imaging technology in optical coherence tomography (OCT) has advanced rapidly and contributed greatly to progress in ophthalmology during this decade[1,2]
We applied B-spline-based elastic registration to adaptive optics scanning laser ophthalmoscopy (AO-SLO) videos and demonstrated that the registration enhanced the quality of capillary images constructed from AOSLO video both subjectively and objectively in normal eyes and eyes with various retinal diseases
contrast-to-noise ratio (CNR) for regions of interest (ROI) set on capillary visualized images were approximately twice as high in the E(+) group as in the E(-) group, and the mean score assigned by experts was 3.97 ± 0.70, suggesting that the registration played an important role in capillary visualization
Summary
Imaging technology in optical coherence tomography (OCT) has advanced rapidly and contributed greatly to progress in ophthalmology during this decade[1,2]. Multiple B-scan averaging can visualize microstructure in OCT more clearly than single B-scans, this technique is based on high-speed SD-OCT scanning, by which B-scans are generated with minimal scanning distortion variation from one scan to another. Confocal adaptive optics scanning laser ophthalmoscopy (AO-SLO) has enabled imaging of retinal cells such as photoreceptors and blood cells[10,11,12]. As in OCT, multiple scan averaging has been reported as useful in AO-SLO imaging, with averaged AO-SLO images demonstrating photoreceptor microstructure more clearly than single scans[13,14,15]. Hardware and software for eye tracking have been developed that can stabilize the frames, such as crosscorrelation methods[17] and the KLT (Kanade-Lucas-Tomasi)SIFT (Scale-invariant feature transform) algorithm[14], and excellent photoreceptor imaging results have been reported using these systems[18]
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