These images were aquired with CT following rapid injection of iodinated contrast material through an arm vein. The scan was obtained while the contrast was located in the arterial circulation.
The data has been reformatted into a 3D image with a volume rendering technique. Only high density structures, like the contrast opacified vessels and the skull base, are displayed in this image. View the image as though the calvarium has been removed and you are looking down onto the skull base and circle of Willis.