Regional Cerebral Blood Flow in Stroke by 133Xenon Inhalation and Emission Tomography

A rapidly rotating single-photon emission tomograph was used to study regional cerebral blood flow by 123Xeoon inhalation. Using a rotation speed of 180°/5 sec a tomographic picture of the arerage Xenon concentration in 3 slices is obtained. By taking a sequence of 4 one-minute tomograms during and after a oneminute 123Xenon inhalation period, a flow-dependent variation in local isotope concentration is seen. This sequence is used for calculating CBF by a deconvolution procedure. The CBF maps hare a spatial resolution of approximately 1.7 cm (FWHM). This preliminary study comprises normal subjects and 10 unselected patients with stroke. The CBF tomograms localized appropriate ischemic areas in all 10 patients. In one patient the conventional x-ray tomogram was negative, while the flow toraogram clearly showed a decreased flow in consonance with the clinical findings. Regional cerebral blood flow measured tomographically by 123Xenon inhalation circumvents the extracranial contamination and the superposition of intracranial tissues that hamper 123Xenon inhalation flow studies using stationary detectors.