Contrast-enhanced MR Angiography of Intracranial Giant Aneurysms

77-year-old man with giant basilar artery aneurysm. A–C, On T2-weighted FSE image (A) (5182/99/1), a giant basilar artery aneurysm is mainly of high signal. Patency of its lumen can therefore not be assumed. Targeted MIP projection of the posterior circulation from the 3D-TOF (B) (35/6/1/20°) sequences, acquired with overlapping slabs, shows the entering vessels, only a small part of the aneurysm sac, and no exiting vessels. Aneurysm and exiting vessels are well seen on dynamic contrast-enhanced MRA sequence (C) (5/2/1/25°)

62-year-old woman with giant aneurysm of left cavernous carotid artery (CCA). A–F, early (A) and late (B) frames of DSA run after left CCA injection. Early frame (A) shows entering vessel and high-velocity inflow jet. Full extent of aneurysm sac and exiting vessels are only shown on late frame of DSA run (B) where visualization of distal vessels is faint owing to turbulent flow and contrast dilution in the aneurysm sac. MIP of 3D-TOF (C) (40/6.9/1/20°) and contrast-enhanced 3D-TOF (D) (40/6.9/1/45°). Precontrast 3D-TOF (C) shows only entering vessels and high-velocity inflow jet, similar to early frame of the DSA (A), accounting for different projection angle, whereas contrast-enhanced 3D-TOF (D) also shows aneurysm sac and distal vessels. Axial source images of 3D-TOF (E) and contrast-enhanced 3D-TOF (F) show intraluminal clot. Low signal clot adherent to posterolateral wall of aneurysm is visible on 3D-TOF axial source images (E), but dropout of signal from nonlaminar flow anteriorly does not allow exclusion of additional clot. Interface between patent aneurysm lumen and low signal clot is much clearer on axial source images of contrast-enhanced 3D-TOF (F)