In vivo accuracy of multisequence MR imaging for identifying unstable fibrous caps in advanced human carotid plaques

Purpose: To evaluate the in vivo accuracy of a multisequence MRI technique for prospectively identifying one feature of the vulnerable plaque-an unstable fibrous cap-in human carotid atherosclerosis. Materials and Methods: The carotid arteries of 18 endarterectomy patients were preoperatively imaged in a 1.5T scanner using a multisequence protocol that generated four contrast weightings (3D time of flight (ToF), T1, proton density (PD), and T2) at each slice location. With the use of previously published MR criteria, the images of the vessel wall were first examined for evidence of an unstable fibrous cap. The imaging findings were then correlated with the histology from the surgical specimens. Results: A blinded review of the MR findings with the histologic state of the fibrous cap revealed that 1) assessing the preoperative appearance of the fibrous cap has a high test sensitivity (0.81) and specificity (0.90) for identifying an unstable cap in vivo; and 2) the availability of different contrast weightings facilitated image interpretation when intimal. calcifications or flow artifacts obscured the lumen surface. Conclusion: Multisequence MRI can accurately characterize the in vivo state of the fibrous cap. This finding supports the use of these noninvasive techniques to prospectively identify vulnerable plaques.