CT angiography is a regular CT scan with dye injected into the arteries and veins to also illuminate these vessels. This test is not a CT myelogram where dye is injected into the nerve sac (dural sac) to illuminate the nerves and spinal cord.
CT scans a very good for looking at the bone of the spine. You can see vertebra, changes in the bone from wear (bone spurs and cysts), the foramen (the exits of the nerve root), the facets and the spinal canal.
You cannot see with clarity the spinal cord or any disc herniations as these are not made of bone.
The vertebral arteries are well visualized with the angiogram and if injury or compression are present, these will be seen.