Figure 2. Re-circulation artefact. (a) At the bulb of the internal carotid artery, a filling defect with ill-defined margin is noted (black arrow), showing ambiguous darkness and preservation of posterior wall contour (white arrows) on two-dimensional Fourier transformation time-of-flight MR angiography (2D-FT TOF MRA). (b) No defect is noted on film–screen X-ray contrast angiography.