T1 gadolinium enhancement of intracranial atherosclerotic plaques associated with symptomatic ischemic presentations

Abstract

Background and purpose: Contrast enhancement of intracranial atherosclerotic plaques has recently been investigated using high field and high resolution MR imaging as a risk factor in the development of ischemic stroke. We studied the reliability of conventional MR imaging at 1.5T in evaluating intraplaque enhancement and its relationship with acute cerebrovascular ischemic presentations in patients with severe intracranial atherosclerotic disease.

Materials and methods: We retrospectively identified and analyzed 19 patients with 22 high-grade intracranial atherosclerotic disease plaques (>70% stenosis) in vessels cross-sectionally visualized by neuroanatomic MR imaging. Atherosclerotic plaques were classified as asymptomatic or symptomatic. Two blinded neuroradiologists independently ranked each lesion for the presence of intraplaque enhancement by use of a 5-point scale (1-5). Furthermore, plaque enhancement was quantified as the relative change in T1WI spin-echo signal intensity (postcontrast/precontrast) in the vessel wall at the site of each intracranial atherosclerotic disease lesion.

Results: Intraplaque enhancement was observed in 7 of 10 (70%) symptomatic plaques, in contrast to 1 of 12 (8%) asymptomatic plaques. Interobserver reliability correlated well for intraplaque enhancement (κ = 0.82). The degree of relative plaque enhancement in symptomatic versus asymptomatic lesions (63% versus 23%) was statistically significant (P = .001, t test).

Conclusions: In this pilot study, we determined that intraplaque enhancement could be reliably evaluated with the use of cross-sectional imaging and analysis of vessels/plaques by use of conventional neuroanatomic MR imaging protocols. In addition, we observed a strong association between intraplaque enhancement in severe intracranial atherosclerotic disease lesions and ischemic events with the use of conventional MR imaging. Our preliminary study suggests that T1 gadolinium-enhancing plaques may be an indicator of progressing or symptomatic intracranial atherosclerotic disease.

Figures

Fig 1.

Symptomatic patient with MR DWI (A) demonstrating focal infarcts in the bilateral distributions (white arrows). TOF MR angiography MIP (B) and source images (C) confirm severe stenosis in an A2 azygous ACA segment. Axial T1-weighted-pre (D) and T1-weighted-post contrast (E) images identify enhancing ICAD plaque (inset) involving the azygous A2 ACA segment. Methodology of plaque/wall area measurements are demonstrated (F), with solid black line delineating outer wall boundary and dotted line segmenting the vessel lumen denoted as “L.”

Fig 2.

Asymptomatic patient with history of stroke receiving follow-up imaging. TOF MRA reveals severe basilar stenosis in MIP (A) and source images (B). Axial T1WI precontrast (C) and postcontrast (D) demonstrates nonenhancing ICAD plaque.