Hemi-ellipsoid formula enables accurate assessment of carotid plaque volume and atherosclerotic burden

Carotid atherosclerotic plaques have a three-dimensional shape on initial detection and progress in their contour and size in all three directions over time. To estimate the plaque volume, we measured circumferential (c_p) and sagittal (l_p) length, and mean of luminally protruding thickness (t_mean) from axial and sagittal carotid duplex ultrasonography (CDU) images of the carotid plaques. Then, we calculated plaque volume using the hemi-ellipsoid volume formula (π[c_p × l_p × t_mean]/6) with the three axis values. We logically validated that the hemi-ellipsoid volume formula could be applied to estimate the volume of all plaques with smooth or irregular thicknesses and involving the partial or entire axial lumen. The hemi-ellipsoid volume evaluations were a better tool to assess severity and atherosclerotic burden of carotid atherosclerotic plaques on follow-up than one-dimensional diameter ([1-{stenosis/lumen diameter}] × 100%) and two-dimensional area stenosis ([1-{stenosis/lumen area}] × 100%) evaluations. The present study showed successful implementation of the hemi-ellipsoid volume formula to logically measure plaque volume. The logical volume estimation was better for evaluating and monitoring the severity and atherosclerotic burden of carotid plaques.