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Renal Contrast-enhanced MR Angiography: Timing Errors and Accurate Depiction of Renal Artery Origins¹

¹ From the Departments of Medical Physics (M.A.S.) and Radiology (R.M.), St George's Hospital NHS Trust, London, England. Received August 14, 2007; revision requested October 5; revision received February 7, 2008; accepted March 6; final version accepted April 10. Address correspondence to M.A.S., MRI Unit, Royal Marsden NHS Foundation Trust, Downs Rd, Sutton SM205PT, England (e-mail: maria.schmidt{at}stgeorges.nhs.uk).

Purpose: To investigate bolus timing artifacts that impair depiction of renal arteries at contrast material–enhanced magnetic resonance (MR) angiography and to determine the effect of contrast agent infusion rates on artifact generation.

Materials and Methods: Renal contrast-enhanced MR angiography was simulated for a variety of infusion schemes, assuming both correct and incorrect timing between data acquisition and contrast agent injection. In addition, the ethics committee approved the retrospective evaluation of clinical breath-hold renal contrast-enhanced MR angiographic studies obtained with automated detection of contrast agent arrival. Twenty-two studies were evaluated for their ability to depict the origin of renal arteries in patent vessels and for any signs of timing errors.

Results: Simulations showed that a completely artifactual stenosis or an artifactual overestimation of an existing stenosis at the renal artery origin can be caused by timing errors of the order of 5 seconds in examinations performed with contrast agent infusion rates compatible with or higher than those of hand injections. Lower infusion rates make the studies more likely to accurately depict the origin of the renal arteries. In approximately one-third of all clinical examinations, different contrast agent uptake rates were detected on the left and right sides of the body, and thus allowed us to confirm that it is often impossible to optimize depiction of both renal arteries. In three renal arteries, a signal void was found at the origin in a patent vessel, and delayed contrast agent arrival was confirmed.

Conclusion: Computer simulations and clinical examinations showed that timing errors impair the accurate depiction of renal artery origins.

© RSNA, 2008