Vascular calcification in ex vivo carotid specimens: precision and accuracy of measurements with multi-detector row CT.

Abstract

To test the accuracy and precision of multi-detector row computed tomography (CT)-derived measurements of vascular calcification in ex vivo human carotid endarterectomy (CEA) specimens. Sixteen ex vivo CEA specimens were imaged with multi-detector row CT. Multi-detector row CT-derived calcium scoring algorithms (ie, mineral mass and volume score) were compared with the mass and volume of ashed remnants of the CEA specimens. Bland-Altman analysis was performed to assess the mean (ie, bias) and SD (ie, precision) of differences between multi-detector row CT- and ashing-derived measurements. In addition, conventional Agatston score, volume score, mineral mass, and modified Agatston score were calculated for each specimen by using a number of scanning protocols. Images were obtained at a section thickness of 1.25 mm by using different tube energy settings and tube currents. Specimens were also imaged at different section thicknesses with fixed combinations of tube energy and tube current. To compare measurement variability of scoring methods, coefficients of variation for all protocols were calculated. Both mean multi-detector row CT-derived mineral mass and mean ashing-derived mineral mass were 0.129 g +/- 0.173 (r = 0.99, P <.001). Mean multi-detector row CT- and ashing-derived volumes were 339.94 mm3 +/- 395.4 and 39.48 mm3 +/- 55.76, respectively (r = 0.95, P <.001). Measurement bias relative to the reference ashing values was high (2,800.0%) for volume score and low (2.58%) for mineral mass. Measurement precision was 0.6% for volume score and greater than 0.0005% for mineral mass. Mean coefficients of variation for all CT protocols were 5.0% +/- 4.2 and 4.9% +/- 4.2 for mineral mass and modified Agatston score, respectively, and 16.0% +/- 9.2 and 14.5% +/- 3.9 for conventional Agatston and volume scores, respectively (P <.001). Compared with the conventional volume score, multi-detector row CT-derived mineral mass is a less biased and more precise measurement of the mineral content of nonmoving ex vivo CEA specimens. Mineral mass and modified Agatston score are more reproducible than conventional volume and Agatston scores.