In this study, we will assess the image quality and accuracy of MRA studies acquired using these two contrast agents. In the cases where Digital Subtraction Angiography (DSA) or CT angiography images are available, the results of the study using both contrast agents will be compared to the DSA or CTA findings. All MRA images will be assessed independently by two readers. The readers will be blinded to the clinical symptoms, contrast agent and DSA/CTA results. A five-level system rating for image quality of each arterial segment will be used (1 = non-diagnostic images, 2 = poor image quality, significant blurring/artefacts, diagnosis suspected but not established, 3 = fair quality with established diagnosis, 4=good quality with definite diagnosis, minimal blurring/artefacts, 5 = sharply defined borders, excellent quality image information). Vascular lesions will also be graded on a 1-5 scale. Vessel segment stenoses will be graded using a five-point grading scale as follows: (1) normal; (2) mild (\<50% diameter stenosis); (3) moderate (50% to 74%), severe (75% to 99%); and (5) total occlusion.
Grades 1 and 2 will be considered insignificant, while grades 3 to 5 will be interpreted as significant for diagnostic accuracy testing.
