Subtraction helical CT angiography of intra- and extracranial vessels: technical considerations and preliminary experience.

Background And Purpose: Reported CT angiographic (CTA) subtraction methods are not simple, robust, or real time. We investigated a novel technique for semiautomated digital subtraction CTA of the intracranial and extracranial arteries.

Methods: Thirty patients underwent precontrast (low milliampere-seconds) and postcontrast (pitch, 1.