Cerebral Blood Flow Estimated by 33Xe Clearance Technique

Abstract

RADIOACTIVE XENON (¹³³Xe) inhalation and clearance techniques for the measurement of cerebral blood flow have been described previously.^1-3 It is the purpose of this paper to present in detail our experiences with such a method and to examine the limitations of the method more fully. Principle of Method When the inert gas xenon is mixed with air and breathed, it crosses the pulmonary alveolar membrane and is conveyed by the arterial blood to all parts of the body. The isotope of xenon,¹³³Xe, emits a soft γ-ray of energy equal to 81 kiloelectron volts; thus, cerebral radioactivity, due to the presence of this isotope, can be measured by external scintillation counting. It has been stated^4,5 that the blood flow in the scalp and the scattered radiation from the chest do not contribute significantly to the radioactivity detected in this way. It is suggested that cerebral