Current status of renal artery magnetic resonance imaging: theoretical and practical considerations and the potential role of blood-pool contrast agents.

There has been controversy over whether the newer minimally invasive diagnostic tests for renovascular hypertension can provide an accurate diagnosis of disease. Two recent meta-analyses showed that gadolinium-enhanced 3-D magnetic resonance angiography (MRA) had a sensitivity and specificity of >90%, whereas a large prospective clinical trial showed much lower sensitivity. The most important contributing factors to the poor sensitivity were insufficient spatial resolution, motion artefacts due to long acquisition times and a large number of cases of fibromuscular dysplasia. Spatial resolution has significantly improved over the past few years with the introduction of high-performance gradient systems, parallel imaging and high parallel-imaging acceleration factors and improved surface coil technology. The new techniques facilitate isotropic, submillimetre spatial resolution, with high signal-to-noise ratios while allowing shorter scan times and reducing the amount of time the patient needs to hold his/her breath. These technologies have considerably improved the diagnosis of renal artery stenosis using minimally invasive MRA and enhanced therapeutic decision-making. In the current article, we review the potential added value of using new higher-relaxivity blood-pool contrast agents (such as gadofosveset trisodium [Vasovist, Schering AG, Berlin, Germany]) for combined first-pass and steady-state imaging in patients with suspected renovascular hypertension.