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Dirk-Uwe G Bartsch, Manuel Amador, Amit Meshi, Kunny C Dans, Tiezhu Lin, William R Freeman; Improvements to manual registration of AOSLO image sequences. Invest. Ophthalmol. Vis. Sci. 2018;59(9):660.
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Adaptive-optics scanning laser ophthalmoscopy (AOSLO) records line-by-line video sequences that are subject to motion artifacts. Strip alignment cross-correlation has been the procedure of choice to correct for eye motion. The procedure requires human interaction in finding a reference frame. We are investigating the use of automated cross-correlation to located a suitable reference frame. We also investigated the influence of strip width and strip spacing on the success of the strip alignment cross-correlation.
AOSLO video sequences were recorded with our custom-built instrument using the design by Dubra [Dubra Biomedical Optics Express (2011)]. Images were exported to a workstation with nVidia multicore graphics card running Matlab and NIH ImageJ. We used a set of 50 video sequences taken from the AOSLO. We used automated cross-correlation algorithm (ACCA) (StackReg plugin to NIH ImageJ) to analyze the correlation between subsequent frames. The maximum ACCA was used a screening tool to increase the detection speed of the optimal reference frame for strip alignment. We compared the result of NIH ImageJ plugin to the decision by a trained operator. For the strip width evaluation we varied the strip width between 8 and 40 pixel in steps of 8. For the strip spacing evaluation we varied the spacing between 8 and 40 pixel in steps of 8.
We found that ACCA increased the speed by finding good candidates for a toggle view by a human operator. The strip width and spacing variation had little influence on the resulting size of the image. The most important variable was image quality of the video sequence.
AOSLO is limited in its clinical application by the low yield and long post-acquisition processing time. , it is estimated that for every hour of imaging between 10-20 hours of processing is needed. This severely limited the ability of clinicians to use AOSLO imaging on a routine basis. The high-resolution of the instrument limits the field-of-view. The small field-of-view entails that a large number of images have to acquired to yield a reasonable mosaic of overlapping individual images. In addition, light safely limits the quality of a single frame making it necessary to acquire a series of sequential frames at the same location. Continued advances in image processing and hardware motion correction are required to transform the operation of AOSLO imaging into a routine clinical device.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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