Figure 10c. Intracranial embolic materials. (a) Frontal radiograph of the skull shows a platinum coil (arrow) in a small, distal middle cerebral artery branch. It does not look circular, because it has conformed to the shape of the artery. (b) Massive hemorrhage not controlled by surgery in a 61-year-old man who had undergone radiation therapy for unresectable squamous cancer of the neck. Frontal view from angiography shows that the right external carotid artery has been occluded by multiple platinum coils. (c) Lateral view from angiography shows cyanoacrylate glue (arrow) that occludes an arterial venous malformation. (Courtesy of Gary Duckwiler, Los Angeles, Calif.) (d) On a CT scan, polyvinyl alcohol is difficult to see. If the patient undergoes imaging immediately after embolization, as in this case, the clot produced by polyvinyl alcohol may be seen as a linear area of increased attenuation (arrow).