MR Angiography and Phase-Contrast MRI: Measuring Blood Flow in the Kidney

The assessment of renal vasculature and renal blood flow (RBF) is extremely relevant in the diagnosis and monitoring of a range of renal diseases. Phase-contrast (PC) MRI, which does not require contrast media, allows non-invasive measurement of RBF in each renal artery in a single two-dimensional (2D) slice (2D PC-MRI), and recently also in the branches of the vessel of interest (four-dimensional (4D) flow MRI). Renal PC-MRI is not yet being routinely used in clincial practice, but several studies support its clinical potential. MR angiography (MRA) is routinely used to diagnose renal artery stenosis. Although usually requiring contrast agent administration, promising contrast-free sequences for MRA have recently been developed. This chapter provides a comprehensive overview of PC-MRI and MRA of the renal arteries, including patient preparation, physics and acquisition protocols, post-processing and data analysis methods, common issues and artifacts, and clinical applications, with the aim of fostering their wider adoption. Future multicenter studies are needed to define reference ranges, to provide additional evidence of renal PC-MRI and MRA clinical validity, and to demonstrate their clinical potential as part of a multiparametric renal MRI protocol, ultimately allowing their transfer to clinical practice.