Non-contrast-enhanced MR angiography of the renal arteries with inversion-prepared b-SSFP: A comparison of different imaging protocols

INTRODUCTION: Inversion-prepared b-SSFP imaging is a common technique for non-contrast-enhanced (non-CE) MR angiography (MRA) of the renal arteries [15]. With this method, a slab-selective inversion of the volume of interest is followed by a delay TI and subsequent data acquisition. While inverted stationary tissues recover during TI and appear with low signal, non-inverted blood enters the labeled region and is captured with high signal. Typically, a transverse inversion slab is used for spin-labeling of both kidneys. With this scheme, a fraction of arterial blood in the aorta is inverted that will flow into the renal arteries. Since only those parts of the vasculature will exhibit high signal that are reached within TI by non-inverted blood, we propose to move the labeling edge closer to the vasculature of interest. In the context of renal non-CE MRA, different approaches are reported to deal with respiratory motion. These include the use of navigator MR signals to detect the position of the diaphragm [1-3] or the use of an external belt to monitor the respiratory motion [4-5]. The aim of this abstract is twofold: First, to compare the standard labeling approach with a single transverse inversion slab with a targeted scheme that uses multiple inversion slabs. Second, to compare a strategy that uses ECGtriggering, navigators and shorter TI values versus a respiratory triggered approach with longer TI.