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FIG 2. Example of a DSA false-positive finding for basilar occlusion in a patient with a low- or balanced-flow state due to a severe stenosis of the basilar artery.
A and B, Frontal (A) and lateral (B) middle arterial phase DSA images show selective injection of a dominant left vertebral artery (DSA images shown in anatomic orientation). Note absent cephalad flow in the basilar artery distal to the midbasilar segment (arrow), suggesting basilar artery occlusion.
C, Lateral projection, right ICA injection, middle arterial phase DSA image shows minimal retrograde filling of the distal basilar artery (arrow) through the posterior communicating artery. The midbasilar segment is not visualized, suggesting segmental occlusion of the midbasilar artery.
D, CTA was performed 12 days before DSA. This volume-rendered 3D CTA image, in anatomic orientation, shows a severe, eccentric, focal midbasilar stenosis (arrow); however, the basilar artery is clearly patent. This was verified on the gray-scale 2D source image.
E, Axial 2D curved oblique CTA reformation image, frontal projection, shows focal midbasilar artery stenosis (arrow) with 79% stenosis severity.
F, TOF MRA image with frontal oblique MIP shows a focal flow gap in the midbasilar artery (arrow).
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