Contrast Enhanced MRA

Due to its non-invasive character, MRI has become an attractive alternative for the evaluation of the visceral vessel system. Meaney et al. examined 65 patients with suspected mesenteric ischemia using a 3D CE MRA technique [16]. Overall significant stenoses of the celiac artery and the superior mesenteric artery were identified in 14 patients and correlated with catheter-based angiography. A total of 28 of 30 arteries with correlation were correctly graded; therefore, despite disagreement between MRA and catheter-based arteriography in two patients, the sensitivity of CE MRA was 100% for the diagnosis of mesenteric ischemia while the specificity was 95%. The authors concluded that 3D CE MRA is accurate for the evaluation of the origins of the mesenteric and celiac arteries, but that the spatial resolution is too low for reliable assessment of the IMA. In addition, delineation of the small mesenteric branch vessels was shown to be hampered by the limited spatial resolution of MRA [29].

To be considered also is that development of a strong collateral circulation can prevent major abdominal symptoms in patients with severe alterations of the mesenteric arteries [25,26,29-30]. Thus, other parameters need to be defined for the assessment of chronic mesenteric ischemia (see below).

In a study aimed at optimizing an "all-in-one" imaging protocol for the assessment of potential living donors for liver transplants [31] 3D MRA was shown to be useful in depicting vascular anomalies with regard to the aortic branch vessels. In this study 3D FLASH data sets of the hepatic vasculature were collected before and after intravenous administration of Gd-BOPTA (Multi-HanceĀ®, Bracco Imaging SpA, Milan/Italy) at a dose of 0.2 mmol/kg bodyweight in 38 potential liver donors. After exclusion of patients as potential donors because of insufficient liver mass of the left hepatic lobe (n=5), presence of hepatic pathologies (n=9) or dilated biliary ducts (n=4), 20 patients were available for assessment. 3D CE MRA depiction of the hepatic arterial morphology was shown to correlate with conventional DSA in each of these 20 patients. Specifically, 3D CE MRA correctly identified 3 left hepatic arteries originating from the left gastric artery, 3 aberrant right hepatic arteries originating from the SMA, 2 aberrant origins of both hepatic arteries and one common hepatic artery originating from the SMA.

Vascular complications of liver transplantation are another indication for visceral artery imaging. Stafford-Johnson et al [32] reported on the utility of a contrast-enhanced 3D MRA technique for the evaluation of vascular complications following liver transplantation. In 9 of 11 patients MR-based findings could be confirmed by surgery or catheter-based arteriography. In the remaining two patients, 3D CE MRA overestimated a hepatic artery stenosis in one patient while in the other patient a severe stenosis on 3D CE MRA was subsequently shown to represent three discrete tandem lesions.

In patients with intra-abdominal neoplasms CE MRA can be used for staging purposes prior to surgery. Gaa et al [33] reported promising results using a comprehensive "all-in-one" approach for assessing patients with pancreatic cancer.

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