Magnetic resonance angiography of the peripheral vessels with automatic moving bed infusion tracking

PURPOSE: To investigate the actual diagnostic reliability of the Mobitrack technique with a slow intravenous infusion of paramagnetic contrast agent (CA) in MR Angiography of the peripheral arterial district. MATERIAL AND METHODS: Twelve healthy volunteers (mean age: 34) with no personal or family history of peripheral arterial pathologic conditions, underwent MR Angiography of the peripheral vascular district. A 1.5 T superconductive magnet equipped with automatic table feed was used. In the preliminary phase, the circulation time at the abdominal aorta was optimized and customized for each patient. This was done by performing a pre-targeting Fast Field Echo 2D (FFE 2D) sequence with intravenous administration of 1-2 mL CA by an injector, to evaluate the delay time. A 2D Time of Flight (2D TOF) sequence was then performed for topographic purposes. The partially overlapping volumes were acquired using Fast T1-weighted sequences, intravenous CA administration and an automatic table feed of 10 mm/s. A Fast Field Echo 3D (FFE 3D) T1-weighted sequence with TR/TE/FA: of 6.3/1.6/40 degrees and a slice thickness of 1.5 mm were also performed. Thirty to forty mL CA were slowly administered intravenously at a rate of 0.3-0.6 mL/s. Two blinded readers independently evaluated the images giving one of three diagnostic judgements: 1) arteries were well visualized, 2) heterogeneous arteries with(out) the presence of veins, and 3) arteries seen poorly or not at all. The first two judgements were considered diagnostic. The readers considered 19 different anatomical districts for each patient, giving a total of 190 evaluations. RESULTS: A blinded evaluation of the readers judgements did not indicate a statistically significant difference (agreement: 100%). Overall, 82% of the images were rated as 1, 8.5% as 2 and 8.4% as 3. DISCUSSION: In 174/190 judgements the vessels were rated as 1 or 2, that is of diagnostic value. Judgement 3 was always due to the inability to visualize the medial and/or distal third of the arterial circulation of the leg. CONCLUSIONS: The results of this technique optimization study confirm the overall validity of the Mobitrack technique. However they also indicate that further technical advances are required to ensure maximum diagnostic accuracy in this vascular district.