Characterization of atherosclerotic plaque of carotid arteries with histopathological correlation: vascular wall MR imaging vs. color Doppler ultrasonography (US).

Purpose: To investigate whether the vessel wall MRI of carotid arteries would differentiate at-risk soft plaque from solid fibrous plaque by identifying liquid components more accurately than color Doppler ultrasonography (US).

Materials And Methods: This study included 54 carotid arteries in 54 consecutive patients who underwent carotid endarterectomy. MRI was performed using black-blood fat-suppressed (FS) T1-and FS T2-weighted TSE sequences. A total of 68 major segments of the 54 carotid plaques were grouped into four MR categories based on signal intensity index (SII). MR criteria used for the diagnosis of plaque vulnerability were: at-risk soft plaque including a segment of liquid component (category A or B), solid fibrous plaque (category C or D). The MR and US findings were compared with histopathological findings of endarterectomy specimens.

Results: Intraoperative findings and microscopic examination of endarterectomy specimens revealed 24 at-risk soft plaques and 30 solid fibrous plaques. The sensitivity, specificity, and accuracy for diagnosing at-risk soft plaque are 96%, 93%, and 94% for MR, and 75%, 63%, and 69% for color Doppler US, respectively. The slice-by-slice MR evaluation of carotid wall also revealed detailed information of plaque segments and correlated well with the features of corresponding histologic sections.

Conclusion: Vessel wall MRI with MRI category could have a potential to more accurately diagnose an at-risk soft plaque predominantly composed of liquid components in comparison with color Doppler US.