On contrast-enhanced magnetic resonance angiography of the aortoiliac arteries

Abstract: In contrast-enhanced magnetic resonance angiography (CE-MRA),vascular signal is produced by the acquisition of a T1-weighted magnetic resonance imaging scan while the presence of a contrast agent induces a low T1 in blood. In this thesis,CE-MRA of the aortoiliac arteries was evaluated.Different contrast agents and techniques for synchronisation of the scan with the contrast bolus passage were assessed.In 30 patients with clinically suspected iliac artery stenoses,contrast-enhanced magnetic resonance angiography was compared with duplex ultrasound scanning and digital subtraction x-ray angiography (DSA),with intraarterial pressure measurements as reference method. No statistically significant differences in sensitivity or specificity were observed between the techniques regarding the detection of hemodynamically significant iliac stenoses. The use of multiplanar reformats and source images in the MRA examinations was of value for the differentiation between high-grade stenoses and occlusions. With DSA as reference method, MRA had significantly higher sensitivity and specificity than duplex for the detection of ≥50% stenoses.In fourteen patients examined with iliac artery MRA, differences in contrast arrival time of up to 7 s was observed between the aorta and the common femoral artery.A dual-station timing technique adjusting for this difference was found feasible. Compared with a fluoroscopically triggered technique (n=13),which is used in clinical rotine, the dual-station technique was more reliable for the visualisation of distal vessels.In a clinical phase II study comparing different doses of t he contrast agent gadobenate dimeglumine for the enhancement of iliac artery MRA, a significant improvement in subjective diagnostic quality compared with time-of-flight MRA was found at all doses from 0.025 mmol/kg.An increasing trend with dose was observed up to a dose level of 0.05-0.1 mmol/kg.In a phase I clinical study on the intravascular, iron oxide contrast agent NC100150 Injection, a positive dose response was observed for abdominal vascular enhancement, with the highest contrast-to-noise ratio observed at 4.0 mg Fe/kg bw at 1.5 T and at 2.5-4 mg Fe/kg bw at 0.5 T.At 1.5 T higher R2'values were calculated for the aorta than for the IVC.