Figure 1. Re-circulation artefact. (a) An ill-defined filling defect is noted at the bulb of the internal carotid artery, appearing as an ambiguous shadow (arrows) with preservation of posterior wall contour on two-dimensional Fourier transformation time-of-flight MR angiography (2D-FT TOF MRA). The common carotid artery is not involved. (b) No filling defect is noted on film–screen X-ray contrast angiography.