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Jui-Kai Wang, Randy H. Kardon, Mark J. Kupersmith, Mona K. Garvin; Automated SD-OCT Volumetric Estimation Of Severe Papilledema: Overcoming Truncated Scans. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3922.
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Spectral-domain optical coherence tomography (SD-OCT) enables volumetric information of the optic nerve head (ONH) to be acquired. However, in some severe papilledema cases, the optic discs are too swollen to be fully enclosed by the SD-OCT scan window in the z-plane, causing the "top of the iceberg" to be cut off. In such scans, the border of the internal limiting membrane (ILM) is missing from the portion of the nerve projecting the furthest into the vitreous. An automated method was developed to interpolate the missing ILM to more correctly estimate the corresponding disc volume.
Eleven complete 3-D SD-OCT (Zeiss Cirrus) ONH-centered scans of 11 papilledema subjects (from The University of Iowa) were segmented by our 3-D graph-theoretic algorithm and the volume between the ILM and the retinal pigment epithelial (RPE) complex in each scan was computed, where the SD-OCT scans were flattened in 3-D so the RPE complex became a flat reference plane. Then, 50, 100, 150 voxels from the same scans were artificially cut off from the ILM tip of each scan, and the reduced disc volumes were re-computed. Finally, the missing partial ILM in the artificially truncated scans was regenerated by our new thin-plate-spline interpolation approach, and the corrected volumes were computed.
When the SD-OCT scans were artificially truncated by 50, 100, and 150 voxels, the average absolute errors of the truncated volumes were: 0.045, 0.236 and 0.565 mm3. The average absolute errors of the corrected volumes were significantly smaller (p < 0.001): 0.044, 0.035 and 0.120 mm3.
Volumetric quantification of severe papilledema can be inaccurate when the swollen disc will not conform to the dimensions of the OCT measurement window causing them to be truncated. By regenerating the missing ILM by interpolation and computing the corrected disc volume, the volumetric measurement for papilledema becomes more reliable.
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