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Giant cell (temporal) arteritis is a diagnostic challenge. Blindness is a dreaded complication, especially if high-dose steroid treatment is delayed. With an optimized MR protocol, noninvasive diagnosis of giant cell arteritis is facilitated. Submillimeter in-plane resolution makes it possible to distinguish healthy segments from inflamed segments. The lumen and arterial wall can be depicted in high detail. Post-contrast high-resolution MRI visualizes the superficial cranial arteries bilaterally and simultaneously, allowing assessment of the cranial involvement pattern. In combination with MR angiography of the aortic arch and supra-aortic arteries, the extracranial involvement pattern can be demonstrated in a single comprehensive MR examination assessing the cranial, cervical and thoracic vasculature. Good diagnostic image quality can be achieved at 1.5 Tesla and at 3 Tesla. However, due to higher signal-to-noise ratios, image quality seems to be superior at 3 Tesla. Over the course of successful long-term treatment, MR signs of mural inflammation decrease significantly and eventually vanish entirely. In contrast to color-coded Duplex sonography, which is a comparatively cost-efficient imaging modality, acquisition of high-resolution MRI is almost independent of the investigator's expertise. Compared to positron emission tomography with 18F-fluoro-2-deoxy-D-glucose, which is a very sensitive whole-body screening tool for detecting extracranial involvement of large vessel vasculitis, MRI allows visualization and assessment of both the superficial cranial arteries in high detail and the extracranial large artery involvement in the same investigation.

Modern phase contrast MR imaging at 3 Tesla allows the depiction of 3D morphology as well as the acquisition of time-resolved blood flow velocities in 3 directions. In combination with state-of-the-art visualization and data processing software, the qualitative and quantitative analysis of hemodynamic changes associated with vascular pathologies is possible. The 4D nature of the acquired data permits free orientation within the vascular system of interest and offers the opportunity to quantify blood flow and derived vessel wall parameters at any desired location within the data volume without being dependent on predefined 2D slices. The technique has the potential of overcoming the limitations of current diagnostic strategies and of implementing new diagnostic parameters. In light of the recent discussions regarding the influence of the wall shear stress and the oscillatory shear index on the genesis of arteriosclerosis and dilatative vascular processes, flow-sensitive 4D MRI may provide the missing diagnostic link. Instead of relying on experience-based parameters such as aneurysm size, new hemodynamic considerations can deepen our understanding of vascular pathologies. This overview reviews the underlying methodology at 3T, the literature on time-resolved 3D MR velocity mapping, and presents case examples. By presenting the pre- and postoperative assessment of hemodynamics in a thoracic aortic aneurysm and the detailed analysis of blood flow in a patient with coarctation we underline the potential of time-resolved 3D phase contrast MR at 3T for hemodynamic assessment of vascular pathologies, especially in the thoracic aorta.

Ziele: Es war das Ziel, mittels fluss-sensitiver 4D MRT und farbkodierter Visualisierung die Abhangigkeit der aortalen Hamodynamik vom Aortendurchmesser auszuwerten und nachzuweisen, dass ektatische Aorten einen deutlichen veranderten Blutfluss zeigen. Methode: Die Messungen wurden an einem 3T-Scanner (TRIO, Siemens) mit einer 8-Kanal Oberflachenspule nach Aufklarung und Einverstandnis an 62 Patienten (50,6±18,9 Jahre, 73,1±10,6kg, 25 Frauen) durchgefuhrt. Eine 3-direktional fluss-sensitive 3-dimensionale Gradientenechosequenz wurde mit den Parametern: Geschwindigkeitssensitivitat=150cm/s, Ortsauflosung=(2.71–2.93×1.58–1.69×2.60–3.0)mm3, zeitliche Auflosung=48.8ms angewendet. Die Visualisierung und Platzierung von 8 Auswerteschichten in der Aorta erfolgte mittels Ensight (CEI, USA). Ermittelt wurden: Durchmesser der Aorta ascendens (AAo), Helizitat des Fluss, Vortexbildung, -dauer und –lokalisation, Lokalisation und Zeit zum maximalen arteriellen Fluss (TTP) je positionierter Schicht und Dauer des retrograden Fluss. Als Gruppierungsmerkmal diente der Durchmesser der AAo in kleine Aortendiameter (KAD-Gruppe ≤3,5cm, MW 2,8±0,4cm) und erweiterte Diameter (EAD-Gruppe >3,5cm, MW 3,8±0,4cm) Ergebnis: Die KAD-Gruppe zeigte eine signifikant geringere Zahl an deutlich kurzer nachweisbaren Vortices (KAD=1,3±1,1; EAD 2,3±0,9; p3,5cm) signifikante Anderungen der Hamodynamik erfahren. Mit Hinblick auf das flussinduzierte arterielle Remodeling wird damit verdeutlicht, dass der Analyse der Hamodynamik bei geometrischen Veranderungen der Aorta zukunftig eine grosere Bedeutung zum therapeutischen Prozedere zukommen konnte. Korrespondierender Autor: Frydrychowicz A Universitatsklinikum Freiburg, Diagnostische Radiologie, Hugstetter Str. 55, 79106 Freiburg E-Mail: alex.frydrychowicz@uniklinik-freiburg.de