Functional applications of CT of the central nervous system.

Although CT has developed as a morphologic technique, its anatomic specificity may be used to map physiologic events. Using intravenously infused iodinated contrast media, CT offers unique analysis of the integrity of the blood-brain barrier. If the barrier is not disrupted, the same iodinated indicators may be used to estimate vascular transit time and cerebral blood volume. Nonradioactive xenon, a freely diffusible indicator, enhances the brain substance and may be used to evaluate both cerebral blood flow and tissue integrity in well defined anatomic locales. However, these functional determinations have distinct limitations. Future use of CT, including providing more sophisticated tissue characterization, indicator development, and advances in scanner technology, are discussed.