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For imaging of atherosclerotic disease, lumenography using computed tomography, ultrasonography, or invasive angiography is still the backbone of evaluation. However, these methods are less effective to predict the likelihood of future thromboembolic events caused by vulnerability of plaques. PET and MR imaging have been used separately with success for plaque characterization. Where MR imaging has the ability to reveal plaque composition, PET has the ability to visualize plaque activity. Together this leads to a comprehensive evaluation of plaque vulnerability. In this review, the authors go through data and arguments that support increased use of PET/MR imaging in atherosclerotic imaging., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Objective: A feature of vulnerable atherosclerotic plaques of the carotid artery is high activity and abundance of lesion macrophages. There is consensus that this is of importance for plaque vulnerability, which may lead to clinical events, such as stroke and transient ischemic attack. We used positron emission tomography (PET) and the novel PET ligand [(64)Cu] [1,4,7,10-tetraazacyclododecane-N,N',N″,N‴-tetraacetic acid]-d-Phe1,Tyr3-octreotate ((64)Cu-DOTATATE) to specifically target macrophages via the somatostatin receptor subtype-2 in vivo., Approach and Results: Ten patients underwent simultaneous PET/MRI to measure (64)Cu-DOTATATE uptake in carotid artery plaques before carotid endarterectomy. (64)Cu-DOTATATE uptake was significantly higher in symptomatic plaque versus the contralateral carotid artery (P<0.001). Subsequently, a total of 62 plaque segments were assessed for gene expression of selected markers of plaque vulnerability using real-time quantitative polymerase chain reaction. These results were compared with in vivo (64)Cu-DOTATATE uptake calculated as the mean standardized uptake value. Univariate analysis of real-time quantitative polymerase chain reaction and PET showed that cluster of differentiation 163 (CD163) and CD68 gene expression correlated significantly but weakly with mean standardized uptake value in scans performed 85 minutes post injection (P<0.001 and P=0.015, respectively). Subsequent multivariate analysis showed that CD163 correlated independently with (64)Cu-DOTATATE uptake (P=0.031) whereas CD68 did not contribute significantly to the final model., Conclusions: The novel PET tracer (64)Cu-DOTATATE accumulates in atherosclerotic plaques of the carotid artery. CD163 gene expression correlated independently with (64)Cu-DOTATATE uptake measured by real-time quantitative polymerase chain reaction in the final multivariate model, indicating that (64)Cu-DOTATATE PET is detecting alternatively activated macrophages. This association could potentially improve noninvasive identification and characterization of vulnerable plaques., (© 2015 The Authors.)

Noninvasive imaging of atherosclerosis could potentially move patient management towards individualized triage, treatment, and followup. The newly introduced combined positron emission tomography (PET) and magnetic resonance imaging (MRI) system could emerge as a key player in this context. Both PET and MRI have previously been used for imaging plaque morphology and function: however, the combination of the two methods may offer new synergistic opportunities. Here, we will give a short summary of current relevant clinical applications of PET and MRI in the setting of atherosclerosis. Additionally, our initial experiences with simultaneous PET/MRI for atherosclerosis imaging are presented. Finally, future potential vascular applications exploiting the unique combination of PET and MRI will be discussed.

Background: Knowledge of the natural course after an ST-elevation myocardial infarction (STEMI) treated according to guidelines is limited because comprehensive serial magnetic resonance imaging (MRI) of systolic left ventricular function, edema, perfusion, and infarct size after STEMI has not been undertaken. The aim of this study was to evaluate effects of therapy for STEMI on left ventricular function and perfusion and to test the hypothesis that myocardial perfusion by MRI predicts recovery of left ventricular function., Methods: Cine MRI, edema, first-pass perfusion, and late enhancement imaging were performed in 58 patients at day 2 and at 1 and 6 months after successful primary percutaneous coronary stent intervention for STEMI., Results: Ejection fraction increased 6.3% during the first month (P < .001) and 1.9% from 1 to 6 months (P < .06), indicating a maximal recovery very early after the infarction. The systolic wall thickening in the infarct area almost doubled (P < .001), the perfusion of infarcted myocardium increased approximately 50% (P = .02), and perfusion improved in 72% of patients. Edema decreased with a mean of 2 segments (P < .001) during the first month and another 2.5 segments from 1 to 6 months (P < .001). Infarct size decreased to 1 month (P = .01) and was unchanged from 1 to 6 months (P = .5). Baseline perfusion did not predict improvement in ejection fraction (r = 0.2, P = .2) but did predict regional systolic function (P = .03)., Conclusions: Left ventricular function, perfusion, and infarct mass recovered substantially after STEMI, with the main part of the change within the first month. First-pass perfusion at rest appeared to predict regional ventricular recovery.