Comparison of symptomatic and asymptomatic atherosclerotic carotid plaque features with in vivo MR imaging

Abstract

Purpose: To retrospectively determine if in vivo magnetic resonance (MR) imaging can simultaneously depict differences between symptomatic and asymptomatic carotid atherosclerotic plaque.

Materials and methods: Institutional review board approval and informed consent were obtained for this HIPAA-compliant study. Twenty-three patients (21 men, two women; mean age, 66.1 years +/- 11.0 [standard deviation]) with unilateral symptomatic carotid disease underwent 1.5-T time-of-flight MR angiography and 1.5-T T1-, intermediate-, and T2-weighted MR imaging. Both carotid arteries were reviewed. One observer recorded quantitative and morphologic information, which included measurement of the area of the lumen, artery wall, and main plaque components; fibrous cap status (thick, thin, or ruptured); American Heart Association (AHA) lesion type (types I-VIII); and location (juxtaluminal vs intraplaque) and type of hemorrhage. Plaques associated with neurologic symptoms and asymptomatic plaques were compared with Wilcoxon signed rank and McNemar tests.

Results: Compared with asymptomatic plaques, symptomatic plaques had a higher incidence of fibrous cap rupture (P = .007), juxtaluminal hemorrhage or thrombus (P = .039), type I hemorrhage (P = .021), and complicated AHA type VI lesions (P = .004) and a lower incidence of uncomplicated AHA type IV and V lesions (P = .005). Symptomatic plaques also had larger hemorrhage (P = .003) and loose matrix (P = .014) areas and a smaller lumen area (P = .008). No significant differences between symptomatic and asymptomatic plaques were found for quantitative measurements of the lipid-rich necrotic core, calcification, and the vessel wall or for the occurrence of intraplaque hemorrhage or type II hemorrhage.

Conclusion: This study revealed significant differences between symptomatic and asymptomatic plaques in the same patient.

Figure 1

Transverse MR images of a complicated AHA type VI lesion in the left common carotid artery of an 81-year-old patient who experienced ipsilateral neurologic symptoms 3 months before MR imaging. A surface irregularity and a hyperintense juxtaluminal signal (arrow) visible on the TOF angiogram (23.0/3.5) indicate a fibrous cap rupture or ulcer. A hyperintense area (chevron) visible on TOF, T1-weighted (T1W) (800.0/9.3), intermediate-weighted (IMW) (3500/10), and T2-weighted (T2W) (3500/40) images indicates a necrotic core with type II hemorrhage.

Figure 2

Transverse TOF (23.0/3.5) MR angiogram and T1-weighted (T1W) (800.0/9.3), intermediate-weighted (IMW) (2769/10), and T2-weighted (T2W) (2769/70) MR images of a complicated AHA type VI lesion in the left internal carotid artery of a 48-year-old patient who experienced four episodes of amaurosis fugax in the 4 months before MR imaging. An irregularly shaped intraluminal hyperintense area (arrow) is visible on intermediate-and T2-weighted images in the left internal carotid artery. This finding is indicative of mural thrombus.

Figure 3

Transverse TOF (23.0/3.5) MR angiogram and T1-weighted (T1W) (800.0/9.3), intermediate-weighted (IMW) (3000/10), and T2-weighted (T2W) (3000/70) MR images of an uncomplicated type IV and V lesion in the left internal carotid artery (*) on the asymptomatic side in a 62-year-old patient. The homogeneous appearance of the eccentric plaque (arrow) on T1-, intermediate-, and T2-weighted MR images, with a smooth lumen surface and a dark band on TOF MR angiograms, indicates the presence of a thick fibrous cap.