Zeitaufgelöste MR-Angiografie der Becken-Bein-Etage: ein Lösungsansatz für das Problem der venösen Überlagerungen

Zusammenfassung

Ziel: Ziel dieser Studie war die Evaluation einer 3-stufigen MRA-Technik mit zeitaufgelösten Messungen an Ober- und Unterschenkeln hinsichtlich unerwünschter venöser Überlagerungen. Material und Methoden: In dieser retrospektiven Studie wurde bei 150 Patienten an einem 1,5 T System eine Becken-Bein-MRA nach einem 3-stufigen Protokoll mit 3 KM-Teilinjektionen (Menge: je 0,1 mmol/kg eines 1-molaren KM) durchgeführt. An der Ober- und Unterschenkeletage kamen zeitaufgelöste Messungen zum Einsatz. Die Auswertung erfolgte hinsichtlich Vorhandensein und Ausprägung unerwünschter venöser Überlagerungen bzw. des Auftretens inadäquaten Kontrastmittel-Timings. Ergebnisse: Generell war die MRA technisch erfolgreich durchführbar, die allgemeine Bildqualität in 127 / 150 Fällen exzellent (84,7 %), in 21 Fällen (14,0 %) leicht eingeschränkt bzw. in 2 Fällen (1,3 %) noch ausreichend. Eine unzureichende Bildqualität lag in keinem Fall vor. In den meisten Fällen wurde keine venöse Überlagerung gefunden (139 / 150, 92,7 %). Geringfügige bzw. moderate Überlagerungen, diagnostisch nicht relevant, wurden in 7 Fällen (4,6 %) bzw. in 4 Fällen (2,7 %) gefunden. Eine relevante Überlagerung lag in keinem Fall vor. In den 11 Fällen leichter Überlagerung trat diese in 8 Fällen isoliert am Unterschenkel, in 2 Fällen am Ober- und Unterschenkel und in einem Fall isoliert am Oberschenkel auf. Klinisch lag in 10 der 11 Fälle mit venöser Überlagerung eine schwere pAVK im klinischen Stadium IV vor. Schlussfolgerung: Die 3-stufige MRA der Becken-Bein-Etage mit dynamischer Messung von Ober- und Unterschenkeln ist ein suffizientes Verfahren für die Praxis, wobei neben dem Problem von Laufzeitunterschieden die Problematik einer eingeschränkten diagnostischen Sicherheit durch venöse Überlagerungen und Verfehlen des arteriellen Bolus nicht mehr besteht.

Abstract

Purpose: The aim of this retrospective study was to evaluate peripheral MRA using time-resolved measurements at the femoral as well as the calf level with regard to the presence of unwanted venous overlap. Materials and Methods: 150 patients were examined using a 1.5 T MRI unit for a three-step CE MRA approach with three partial injections of contrast agent (0.1 mmol/kg body weight of 1 molar contrast agent). Dynamic time-resolved measurements were used at the femoral as well the calf level. The images were analyzed with respect to the presence and grade of unwanted venous overlap as well as inadequate bolus timing. Results: In all cases, MRA was technically successful. The overall image quality was assessed as excellent in 127 / 150 cases (84.7 %), as mildly limited in 21 cases (14 %) and as moderately limited, but still diagnostic in 2 cases (1.3 %). No obvious overlap was found in 139 of 150 cases (92.7 %). Non-diagnostically relevant minor overlap was found in 7 cases (4.6 %) and non-diagnostically relevant moderate overlap in 4 cases (2.7 %). Relevant venous overlap did not occur. Those 11 cases with minor or moderate overlap occurred at the calf level in 8 cases, at the calf and femoral level in 2 cases and at the femoral level only in one case. In 10 out of 11 cases, peripheral artery occlusive disease was classified as category IV (Fontaine). Conclusion: Three-step time-resolved CE MRA with dynamic measurements at the calf as well the femoral level can be considered as a safe and accurate technique for MRA of the lower limbs without significant venous overlap and without risk of inadequate bolus timing. Furthermore, it solves the problem of run time differences.

arteries - CE MRA - peripheral arterial occlusive disease - single-step technique - time-resolved MRA - venous overlap

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