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Milton Wei; OCT Angiography Volume Image Compression. Invest. Ophthalmol. Vis. Sci. 2016;57(12):457.
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© ARVO (1962-2015); The Authors (2016-present)
Oct angiography scans contain phase information as well as intensity information. The purpose is to reach maximum compression for both phase and intensity volume images without losing any pathology information contained in the original angiography OCT scans.
Different image compression formats including JPEG, JPEG-LS, PNG etc. were used to compress intensity volume and phase volume of OCT angiography scans of eye patients. A variety of compression rate from 5% to 50% were used for each compression format. Segmentation results of processed intensity volumes (recovered or uncompressed from compressed images) and original intensity volumes were compared to make sure that ILM, RPE etc. layers were still correctly segmented. Enface or slab calculation of phase volume were used to judge if any pathology information was lost during compression. Since enface calculation was also based on the segmentation results of intensity volume, to make thing simple, only the segmentation results of original volume were used. And then slabs calculated from the processed phase volume images for each level of compression rate were compared to the results calculated from original phase volumes. Compression time was also recorded and was considered as another factor. However due to the improvement of compression tools and computer speed, the compression performance was not as critical as the quality.
Some types of compression on intensity volume showed artifacts which had impact on segmentation results. The situation became worse when higher compression rates were used for these type of compression formats. So they were not suitable as compression methods for OCT intensity volume images. However, phase volumes compressed by different kind of compression format and rate did not show significant differences on enface or slab results. So we had big freedom to choose compression method and rate on phase volumes.
The compression format and maximum compression rate without losing any important pathology information were decided for both intensity and phase volume of OCT angiography scans.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
Segmentation results comparison - one from compressed intensity volume, the other is from orignal volume
Slabs calcated form compressed phase volume and from orignal phase volume
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