Lorenzo Mannelli MD, PhD, Presenter: Nothing to Disclose

Lee M. Mitsumori MD, MS, Abstract Co-Author: Nothing to Disclose

Marina Ferguson MS, Abstract Co-Author: Nothing to Disclose

Dongxiang Xu PhD, Abstract Co-Author: Nothing to Disclose

Baocheng Chu, Abstract Co-Author: Nothing to Disclose

Kelley Branch MD, Abstract Co-Author: Speakers Bureau, Pfizer Inc

William Phelps Shuman MD, Abstract Co-Author: Research grant, General Electric Company

Chun Yuan PhD, Abstract Co-Author: Research grant, Koninklijke Philips Electronics NV

The aims of this study are: 1) Determine if changes occur in the perceived size of plaque calcifications on monochromatic images reconstructed at different keV from dual energy CT scans of human carotid endarterectomy (CEA) specimens. 2) Compare the threshold defined size of the calcifications measured on the different keV images to a histologic standard.

Five ex vivo CEA specimens were scanned with dual energy CT. CT Images were reconstructed at 7 different monochromatic energies (40, 60, 77, 80, 100, 120, and 140 keV). The CT scan parameters were: mA 450, kVp 140, slice thickness 0.625 mm. Cross-sectional area of the plaque calcifications present on each CT image was measured using a density threshold of 130 HU. The histologic calcium areas on each corresponding CEA specimen was manual traced on digitized images from specimen sections prepared with a Toluidine Blue/Basic Fuchsin stain. The CT images and corresponding histology slices were then matched based on location from the edge of the specimen, and the shape and size of the calcified and noncalcified plaque components. The CT derived calcium areas on each keV image were then compared with the plaque calcification areas obtained from histology.

Dual energy CT derived plaque calcification areas showed better correlation with histology when made on monochromatic keV images < 100 keV (0.80 < r < 0.86 and p < 0.001), then when done on the higher values of 120 and 140 keV ( r = 0.53 and r = 0.13). The total calcium area for the analyzed specimens on each monochromatic keV image set (40, 60, 77, 80, 100, 120, and 140 keV) were respectively 397 mm2, 267 mm2, 165 mm2, 149 mm2, 69 mm2, 27 mm2, and 3 mm2. The plaque calcium area determined with histology was 139 mm2. There was a statistically significant difference between the plaque calcium areas measured from images obtained using keV ≤100 vs. keV > 100 (p < 0.05).

Dual energy CT attenuation based measurement of the amount of atherosclerotic plaque calcification can be significantly different depending upon the monochromatic energy image reconstruction evaluated. In this study, the calcium area measured on the 80 keV image set was the most similar to the amount of calcium measured on histology

Dual energy CT with monochromatic keV image reconstruction may allow the reduction of calcium blooming artifacts that can limit CT imaging assessment of atherosclerotic plaques.

Mannelli, L, Mitsumori, L, Ferguson, M, Xu, D, Chu, B, Branch, K, Shuman, W, Yuan, C, Changes in the Measured Size of Atherosclerotic Plaque Calcifications in Dual-Energy CT of ex Vivo Carotid Endarterectomy Specimens: The Affect of Different Monochromatic keV Image Reconstructions.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11003692.html