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 endovascular
treatment after detection of a ruptured aneurysm with
CTA. Another new technique, dual-energy CTA, has diagnostic
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