These images were aquired by rapid injection of iodinated contrast material through a catheter placed into the right internal carotid artery, with rapid sequential radiographs obtained.
The image is aquired in an antero-posterior (AP) projection, which optimizes viewing of the internal carotid artery bifurcation. The cavernous segment of the carotid artery is superimposed, and the bifurcation of the middle cerebral artery is not well visualized in this projection.
On this image, the bones are included. On the subsequent images, the bones have been 'subtracted', which increases the conspicuity of the opacified vessels.