Role of computed tomography voxel size in detection and discrimination of calcium and iron deposits in atherosclerotic human coronary artery specimens

Objective:: This study evaluated the influence of voxel size on its ability to discriminate calcium from iron deposits in ex vivo coronary arteries. Methods:: Postmortem human coronary arteries underwent multislice computed tomographic scan at (600-μm) voxel size to provide an index of computed tomography (CT) image noise and synchrotron-based micro-CT at (4-μm) voxel size to provide data for generating a range of voxel sizes 4 to (600-μm) after grayscale noise was added to the projection images before reconstruction so as to mimic the effect of retaining the same radiation exposure involved in the multislice computed tomographic scan. Results:: At voxel sizes of (20-μm) or smaller, iron deposits could be identified based on CT grayscale value. Voxels of (100-μm) or larger cannot resolve nor distinguish iron deposits from calcifications by virtue of CT grayscale value. Conclusions:: Clinical CT scanners cannot be expected to discriminate iron deposits from calcifications by their CT value alone in the arterial wall.