Spurious absence of signal on 3D time-of-flight MR angiograms on 1 and 3 tesla magnets in cerebral arteries associated with a giant ophthalmic segment aneurysm: the need for alternative techniques.

There are many high-resolution MR angiographic techniques available today for the evaluation of circle of Willis. We report a case of bilateral aneurysms of the carotico-ophthalmic segment, the left one being a giant aneurysm, in a 41-year-old woman. She underwent different MRA sequences on both 1 and 3Tesla magnets and a digital subtraction angiography. 3D time-of-flight angiograms can give spurious information on giant aneurysms and other techniques like phase contrast and dynamic contrast enhanced angiographies can supplement if not replace it. High field strength improves the objective quality of MR angiograms, but in the case of large aneurysms, intra aneurysmal and distal vessel signal loss can be a significant problem.