Basis and clinical study of cerebral blood flow dynamics using non-radioactive xenon

Xe-CT is useful for cerebral blood flow studies as quantitative procedure. It is economical and can be repeated easily. CT scans were performed at every one minute during 3-min inhalation and 3-min exhalation. Xenon gas is used about 5 l at one scan. Exposure dose is 16-28 cGy at each one section. As to reproducibility of blood flow, error was about 12% (5 ml/100 g/min) at vascular field. The error in setting of ROI was less than 2 ml/100 g/min at cerebral hemisphere, but was about 8 ml/100 g/min at deep area such as basal ganglia. Sixty-four percent of 1000 cases examined from 1984 to 1993 were cerebral ischemia patients. Patients' age varied from 1-year to 86-year, and even the patient with disturbance of consciousness could be examined. Xe-CT could detect low condition of blood flow which could not be observed by CT scan in acute stage of brain infarction. Because of the good depth resolution, images of thalamus, high blood flow of putamen and low blood flow of posterior limb of internal capsule could be obtained dominantly in this method than in others. It is possible to examine reserve ability of cerebral blood flow by acetazolamide test. SPECT is good for imaging of whole brain and freeze on demand is needed, but Xe-CT is good when assessment of deep part of brain and alteration of blood flow of specified range are needed. (K.H.)