Characterization of carotid plaques using chemical exchange saturation transfer imaging

The preoperative assessment of carotid plaques is necessary to render revascularization safe and effective. The aim of this study is to evaluate the usefulness of chemical exchange saturation transfer (CEST)-MRI, particularly amide proton transfer (APT) imaging as a preoperative carotid plaque diagnostic tool.

We recorded the APT signal intensity on concentration maps of 34 patients scheduled for carotid endarterectomy. Plaques were categorized into group A (APT signal intensity ≥ 1.90 E-04; n = 12) and group B (APT signal intensity < 1.90 E-04; n = 22). Excised plaques were subjected to histopathological assessment and, using the classification promulgated by the American Heart Association, they were classified as intraplaque hemorrhage-positive [type VI-positive (tVI⁺)] and -negative [no intraplaque hemorrhage (tVI⁻)].

Of the 34 patients, 22 (64.7%) harbored tVI⁺- and 12 (35.3%) had tVI⁻ plaques. The median APT signals were significantly higher in tVI⁺- than tIVI⁻ patients (2.43 E-04 (IQR = 0.98–4.00 E-04) vs 0.54 E-04 (IQR = 0.14–1.09 E-04), p < .001). Histopathologically, the number of patients with tVI⁺ plaques was significantly greater in group A (100%, n = 12) than group B (45%, n = 22) (p < .01). The number of symptomatic patients or asymptomatic patients with worsening stenosis was also significantly greater in group A than group B (75% vs 36%, p < .01).

In unstable plaques with intraplaque hemorrhage and in patients with symptoms or progressive stenosis, the ATP signals were significantly elevated. CEST-MRI studies has the potential for the preoperative assessment of the plaques’ characteristics.