Digital subtraction angiography (DSA) was indicated if there was a diffuse aneurysmal pattern of aSAH, and repeat delayed DSA was required if the initial DSA findings were negative, which led to the detection of a small aneurysm in 14% of cases. When the blood is located in the sulci, CTA should be scrutinized for vasculitis, and DSA is recommended for confirmation.109 Others have shown that CTA may not reveal small aneurysms and that 2- and 3-dimensional cerebral angiography should be performed, especially when the hemorrhage is accompanied by loss of consciousness.110 In cases of diffuse aSAH pattern, most agree that negative CTA should be followed by 2- and 3-dimensional cerebral angiography. In older patients with degenerative vascular diseases, CTA can replace catheter cerebral angiography in most cases if the image quality is excellent and analysis is performed carefully.111 Overlying bone can be problematic with CTA, especially at the skull base. A new technique, CTA-MMBE (multisection CTA combined with matched mask bone elimination), is accurate in detecting intracranial aneurysms in any projection without superimposed bone.112 CTA-MMBE has limited sensitivity in detecting very small aneurysms. The data suggest that DSA and 3-dimensional rotational angiography can be limited to the vessel harboring the ruptured aneurysm before endovas- cular treatment after detection of a ruptured aneurysm with CTA. Another new technique, dual-energy CTA, has diag- nostic image quality at a lower radiation dose than digital subtraction CTA and high diagnostic accuracy compared with 3-dimensional DSA (but not 2-dimensional DSA) in the detection of intracranial aneurysms.113 Cerebral angiography is still widely used in the investiga- tion of aSAH and the characterization of ruptured cerebral aneurysms. 