Non ContrastEnhanced Renal MRA

Many renal MR angiography techniques have been described. Standard non-contrast, flow sensitive sequences include time-of-flight (TOF) and phase contrast (PC) MRA. The image quality of these flow-based techniques is limited by diminished flow in patients with vascular stenosis or parenchymal disease and by motion artifacts due to respiration during acquisition times that are too long for breath-holding. Proximal stenoses (where there is less respiratory motion) are better depicted than distal disease [6]. It is possible to excite blood proximal to the renal arteries and then image the blood after it flows into the renal arteries but this is also limited in patients with slow flow. Black blood MRA [7] and navigator-gated, balanced fast field echo projection MRA with aortic

Renal Vasculature

Fig. 6. Normal variants of renal vasculature

I Right renal artery

II Left renal artery a Accessory right renal artery b Right lower polar artery c Early left renal artery branching

Fig. 6. Normal variants of renal vasculature

I Right renal artery

II Left renal artery a Accessory right renal artery b Right lower polar artery c Early left renal artery branching

Polar Arteries Kidney

Fig. 5a-c. CE-MRA study of a potential living kidney donor with an accessory renal artery on the right and early branching of the left renal artery (a-c). On the whole volume MlP the additional renal artery is hard to detect (a) whereas on the subvolume reconstructions (b, c) it is clearly depicted (arrows). Note that the origin of the accessory renal artery on the left is much better appreciated on the surface rendered image (black arrow in c). (Gd-BOPTA, 0.1 mmol/kg) [Image courtesy of Dr. G. Schneider]

spin labeling [8] offer better visualization of the renal arteries without requiring contrast agents, but again these techniques are limited in patients with disease that disturbs normal renal blood flow.

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