Multibolus technique for measuring the distribution of cerebral blood flow over short intervals in man.

Abstract

Repeated measurements of cerebral blood flow distribution were made in man at 1-minute intervals: a 133 xenon solution was injected into the internal carotid artery, and gamma radiation was recorded extracranially in multiple hemispheric regions. In each study, a full-length 133 xenon clearance curve was recorded for 15 minutes and a series of about 15 equal isotope injections separated by 1-minute intervals was given. Following each injection in this multibolus series, a sudden increase in activity was recorded from each brain region. The complete series yielded a slowly rising sawtooth curve for each region; the perpendicular heights of these curves are a measure of the amount of isotope arriving at each region of the brain following each injection and this amount of isotope is proportional to the flow in the region, according to the bolus-fractionation principle. The reproducibility of the method during steady-state conditions was tested in four subjects, and the standard error of measurement was found to be 4%. In four other subjects a visual memory test was given during five of the determinations, and it caused transient flow changes in the occipital regions.