Imaging local cerebral blood flow by Xenon-enhanced computed tomography ? Technical optimization procedures

Abstract

Methods are described for non-invasive, computer-assisted serial scanning throughout the human brain during eight minutes of inhalation of 27%-30% Xenon gas in order to measure local cerebral blood flow (LCBF). Optimized Xenon-enhanced computed tomography (XeCT) was achieved by 5-second scanning at one-minute intervals utilizing a state-of-the-art CT scanner and rapid delivery of Xenon gas via a face mask. Values for local brain-blood partition coefficients (L lambda) measured in vivo were utilized to calculate LCBF values. Previous methods assumed L lambda values to be normal, introducing the risk of systematic errors, because L lambda values differ throughout normal brain and may be altered by disease. Color-coded maps of L lambda and LCBF values were formatted directly onto CT images for exact correlation of function with anatomic and pathologic observations (spatial resolution: 26.5 cubic mm). Results were compared among eight normal volunteers, aged between 50 and 88 years. Mean cortical gray matter blood flow was 46.3 +/- 7.7, for subcortical gray matter was 50.3 +/- 13.2 and for white matter was 18.8 +/- 3.2. Modern CT scanners provide stability, improved signal to noise ratio and minimal radiation scatter. Combining these advantages with rapid Xenon saturation of the blood provides correlations of L lambda and LCBF with images of normal and abnormal brain in a safe, useful and non-invasive manner.

Changes in Cardio-Ankle Vascular Index in Smoking Cessation

“…Also, the incidence and mortality of coronary artery disease among smokers can be lowered to the levels of non-smokers within 1 − 5 years from smoking cessation 15,16) . Furthermore, Meyer et al 17) reported an increase in cerebral blood flow 3 months after smoking cessation. We therefore measured the CAVI every 3 months as a yardstick.…”

Patterns of cerebral hypoperfusion compared among demented and nondemented patients with stroke.

“…The time course of arrival of the radiopaque gas through the different cerebral volumes of interest was determined by resulting densitometric changes of local Hounsfield numbers (Xe-CT CBF method). 18 Patients and volunteers fasted for 4 hours before each CBF measurement. Participants reclined on a CT table while inhaling 100% oxygen for 2-4 minutes before xenon inhalation.…”

Benefits of the angiotensin II receptor antagonist olmesartan in controlling hypertension and cerebral hemodynamics after stroke

“…CBF and CRC were measured by Xe-CT 15,16,18 during the screening period, and after 8 weeks' treatment. CBF was measured using the stable Xe-CT technique described by Gur et al 16 The patients lay still on the scanner bed, in a quiet, dimly lit room, with their eyes covered and inhaled 30% Xe gas, which is stable, radio-dense, lipid-soluble, and rapidly and freely diffuses across the bloodbrain barrier, for 4 min.…”

“…Using this approach, we assessed the hemodynamic status of patients before and after olmesartan administration, using Xe-CT and an acetazolamide (ACZ) challenge test. 15,16 We also evaluated rehabilitation outcomes.…”