Intracranial applications of digital subtraction angiography.

Digital subtraction angiography (DSA) is becoming an important method of studying the intracranial vascular structures. In patients being evaluated for cervicocerebral atherosclerosis, patency of and flow patterns in the major intracranial arteries can be determined. Quantitative as well as qualitative data on relative hemispheric contrast transit times are obtainable. Intracranial aneurysms and vascular malformations can be demonstrated by intravenous DSA, but this technique is unlikely to replace selective intraarterial catheter angiography for the definitive work-up of these conditions. In selected cases, vascular tumors of the intracranial compartment and skull base can be satisfactorily evaluated by intravenous DSA, particularly if precise and intricate anatomic detail is not required. The dural venous sinuses are optimally demonstrated by this modality. Postoperative intravenous DSA is useful for determining the results of surgical treatment of certain conditions, and is suitable for assessing the patency of surgical bypass grafts. The disadvantages of using intravenous DSA for intracranial studies include poorer spatial resolution as compared to conventional angiography, superimposition of vessels, and serious degradation of image quality by patient motion. When greater selectivity and better resolution are required, intraarterial DSA can be performed. Advantages of intraarterial DSA over conventional angiography include the availability of immediate subtraction images, the ability to use dilute concentrations of contrast agent, and lesser film cost. Intraarterial DSA shortens procedure time when therapeutic embolization is performed.