A new type of susceptibility-artefact-based magnetic resonance angiography: intra-arterial injection of superparamagnetic iron oxide particles (SPIO) A Resovist in combination with TrueFisp imaging: a feasibility study.

The goal of this study was to evaluate the use of super paramagnetic particles of iron oxide (SPIO) as a dark blood contrast agent, in combination with a bright blood steady-state free precession sequence for magnetic resonance angiography (MRA), in an animal model. The original concentration of the SPIO of 500 mmol Fe/l and dilutions to 250, 125, 60, 30, 10 and 5 mmol Fe/l were intra-arterially injected into the aorta of a pig. Then the dilution of 10 mmol Fe/l was chosen for repeated intra-arterial injections into two pigs. During these intra-arterial SPIO injections MR images were acquired with a 1.5 T scanner. Signal intensity measurements were performed in the aorta. The signal-to-noise ratio during SPIO bolus passage was significantly less than during baseline conditions (Fisher's F-ratio 159.8, p < 0.005) or the recovery signal-to-noise ratio (Fisher's F-ratio 144.6, p < 0.005). Also, confirmation of flow distal to the catheter-tip position was possible. The use of SPIO as a dark blood agent in combination with a bright blood MR imaging sequence is feasible. Temporary loss of intraluminal signal occurs due to local decrease of the signal because of induction of local inhomogeneities after mixture the present blood and SPIO solution. It provides immediate information about blood flow distal to the catheter and is a potentially useful to guide intravascular MR-interventional procedures.