Imaging description

Computerized tomographic angiography (CTA) has become the most commonly used first-line imaging exam for detection and characterization of aneurysms of the circle of Willis, although MRA is also used for similar purposes and DSA remains the gold standard in many centers [1]. With its multiplanar reformatting, bone subtraction, and 3D volume rendering capabilities, CTA offers very high sensitivity for detection and accuracy for characterization of intracranial aneurysms, although there remain some limitations [2]. Small aneurysms and aneurysms that are in close proximity to bones can be missed by CTA. Also, venous contamination can pose interpretive difficulties by mimicking or hiding aneurysms and other abnormalities such as dissections or stenoses [3]. A less common problem is mistaking a dural-based mass for an aneurysm. This occurs when a meningioma or other extra-axial mass is in close proximity to the vessels and shows enhancement similar to vessels (Figs. 55.1, 55.2, 55.3). Many, but not all, of the missed findings on CTA can retrospectively be correctly identified, emphasizing the need for improving the interpretive skills of radiologists and the CTA techniques that would allow easier interpretation.