[CT X-ray measurement of cerebral blood flow by stable xenon. Methodology and applications]

The measurement of cerebral blood flow by stable xenon computerized tomography is a tridimensional method that offers an excellent spatial resolution. The quantitative estimation of the cerebral blood flow is based on Fick's principle, transformed by Kety and Schmidt, using stable xenon as indicator, which is an inert and freely diffusible gas. The limitations of this method are related to the necessity for the patient to remain completely immobile during the examination, the low signal/noise ratio and the impossibility of measuring cerebral metabolism. By contrast, this method represents a real advantage in the diagnosis and prognosis of cerebral pathology: it allows the acquisition of a precise cartography of superficial and deep regional blood flows; it can reveal zones under the functional perfusion threshold thank to its capacity to measure very low blood flows; it allows the obtention of additional information in pathologies of tumoral, ischemic or degenerative origin by measuring the partition coefficient. Moreover, this technique is reliable, non invasive and reproducible. Advantages of such measurement are illustrated in revealing epileptic foci in partial seizures resistant to medical treatment, in the prognosis of cerebrovascular accidents and in the therapeutic evaluation of drugs used in animal experiments.