Carotid artery calcium: accuracy of a calcium score by computed tomography-an in vitro study with comparison to sonography and histology.

Objectives: The aim of this study was to compare methods of quantifying calcification of the internal carotid artery.
Materials and Methods: We examined 92 internal carotid artery endarterectomy specimens. Grey scale median (GSM) values were calculated from optimized B-mode scans. The degree of calcification was assessed using radiographic calcification grading. Plaques were processed histologically, and classified into: (1) calcium-rich hard plaques, (2) lipid-rich soft plaques, and (3) combined plaques. The specimens were scanned in CT-scanner. The calcium score was determined as described by Agatston.
Results: Histopathology and GSM results concurred in 39 out of 92 cases (kappa=0.088). There was no significant correlation between the calcium score and the median GSM value (R=0.005; P=0.959). Histology and CT morphology showed a significant concordance (P<0.001). Also CT and radiomorphological classification showed close agreement (R=0.628, P<0.001).
Conclusions: Calcium scores calculated using CT morphology enable precise in vitro evaluation of the calcium content of plaques in the internal carotid. In contrast, grey scale median values do not adequately reflect calcification of plaques.