Pitfalls in the measurement of cerebral blood volume with computed tomography.

The use of contrast material and computed tomography (CT) to measure cerebral blood volume (CBV) is valid only if the agent does not egress into cerebral tissue. Since disruption of the blood/brain barrier is common in cerebral disease states, this raises serious doubt as to the validity of this technique. Studies in experimental animals and patients with cerebral lesions demonstrate that contrast material does egress into the extravascular space. In normal brain tissue, contrast enhancement is comparable to the error in CT. Contrast material also causes transient changes in autoregulation, blood pressure, cerebral blood flow, and CBV.