Artefact on MRA following aneurysm clipping: an in vitro study and prospective comparison with conventional angiography

Using both an experimental model and clinical cases, we looked at the artef act produced by Aesculap titanium-ahoy aneurysm clips on MRA. Experimentall y, the volume affected by artefact was 50 % less when the clip was imaged l ying parallel to the main ferromagnetic field than when lying perpendicular to it. Clinically, MRA was prospectively compared with digital subtraction angiography (DSA) in nine patients who had undergone aneurysm clipping. On e patient with a non-diagnostic MRA due to movement artefact was excluded. In all other cases there was an area of signal loss surrounding the clips, obscuring the immediately adjacent vessel segments. There was good demonstr ation of the adjacent bifurcations in five cases and the contralateral circ ulation was seen well in all patients. In three cases in which the adjacent bifurcations were not seen, considerable vasospasm was suggested by MRA an d confirmed with DSA. In one patient an unclipped contralateral ophthalmic artery aneurysm was identified using both modalities. In this series there were no adverse events relating to clips in either static or time-varying m agnetic fields.