Hochauflösende Bildgebung atherosklerotischer Gefäßwandläsionen der Karotiden durch die Magnetresonanztomografie

Zusammenfassung

Der Schlaganfall ist die dritthäufigste Todesursache in Deutschland mit einer Inzidenz von nahezu 150 000 Todesfällen pro Jahr. Um zerebrovaskuläre Ereignisse zu verhindern, gilt derzeit die Karotisendarterektomie oder alternativ das Stenting der Karotiden als Verfahren der Wahl. Allerdings wird allgemein angenommen, dass der Schweregrad einer Stenose als alleiniges Kriterium nur ein schlechter Prädiktor des klinischen Outcomes und somit eine schlechte Grundlage zur Indikationsstellung operativer oder interventioneller Maßnahmen ist. So profitieren symptomatische und asymptomatische Patienten in einem unterschiedlichem Ausmaß von der Karotisendarterektomie: Um einen Schlaganfall in symptomatischen Patienten mit > 70 % Stenose zu verhindern, müssen 3 - 6 Patienten mit einer Karotisendarterektomie therapiert werden, während es 14 - 17 solcher Operationen bedarf, um einen Schlaganfall in asymptomatischen Patienten mit > 50 % Stenose zu verhindern. Es gilt heutzutage allgemein als akzeptiert, dass neben dem Stenosegrad auch die Zusammensetzung und die Oberflächenbeschaffenheit atherosklerotischer Plaques die Vulnerabilität und damit die Wahrscheinlichkeit, ein zerebrovaskuläres Ereignis zu erleiden, maßgeblich mitbestimmen. In diesem Beitrag soll der derzeitige Stand der Plaque-Bildgebung in den Karotiden durch die Magnetresonanztomografie (MRT) dargestellt werden. Dabei sollen die für die Bildgebung relevante Pathophysiologie der Atherosklerose sowie das Konzept des „vulnerablen Plaques” erläutert werden. Die technischen Aspekte der Plaque-Bildgebung, inklusive der Voraussetzungen der Hard- und Software, sowie die MRT-Sequenzen bzw. -Protokolle werden dargestellt. Der aktuelle Stand der Forschung hinsichtlich des Vergleichs von MRT und Histopathologie, Nachweis der Progression der Atherosklerose und der Auswirkung verschiedener Risikofaktoren wird vorgestellt.

Abstract

Stroke is the third most common cause of mortality in the United States with an incidence rate of approximately 700 000 deaths per year. As a means to prevent cerebrovascular events, current concepts advocate endarterectomy or carotid stenting in patients with advanced carotid disease. Arterial stenosis alone has been shown to be a poor predictor of cardiovascular events and therefore both arterial stenosis and patient symptom status are taken as indications for interventional therapy. Several studies have shown that symptomatic subjects benefit more from a carotid endarterectomy than asymptomatic subjects: 3 - 6 carotid endarterectomies are needed to prevent one stroke per year in symptomatic subjects with > 70 % stenosis compared to 14 - 17 carotid endarterectomies in asymptomatic patients with > 50 % stenosis. It is commonly accepted today that factors other than the degree of luminal stenosis can determine a patient’s symptom status, such as the composition or the superficial structure of atherosclerotic plaque. High-resolution magnetic resonance imaging has overcome the limitations of current angiographic techniques and has emerged as a leading non-invasive imaging modality for atherosclerotic disease, especially within carotid arteries and other large vessels. In this review, the state of the art in MRI of atherosclerosis is presented in terms of hardware and image acquisition protocols. Also, the results of validation studies for measuring lesion size, composition and inflammation will be summarized. Finally, the status of several clinical trials involving MRI of atherosclerosis will be reviewed.

Key words

carotid arteries - vascular - MR imaging - atherosclerosis - vulnerable plaque

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