CBF Change (cbf + change)

Distribution by Scientific Domains
Medical Sciences100%

Selected Abstracts

Perfusion-based functional magnetic resonance imaging,

CONCEPTS IN MAGNETIC RESONANCE, Issue 1 2003
Afonso C. Silva
Abstract The measurement of cerebral blood flow (CBF) is a very important way of assessing tissue viability, metabolism, and function. CBF can be measured noninvasively with magnetic resonance imaging (MRI) by using arterial water as a perfusion tracer. Because of the tight coupling between neural activity and CBF, functional MRI (fMRI) techniques are having a large impact in defining regions of the brain that are activated due to specific stimuli. Among the different fMRI techniques, CBF-based fMRI has the advantages of being specific to tissue signal change, a critical feature for quantitative measurements within and across subjects, and for high-resolution functional mapping. Unlike the conventional blood oxygenation level dependent (BOLD) technique, the CBF change is an excellent index of the magnitude of neural activity change. Thus, CBF-based fMRI is the tool of choice for longitudinal functional imaging studies. A review of the principles and theoretical backgrounds of both continuous and pulsed arterial spin labeling methods for measuring CBF is presented, and a general overview of their current applications in the field of functional brain mapping is provided. In particular, examples of the use of CBF-based fMRI to investigate the fundamental hemodynamic responses induced by neural activity and to determine the signal source of the most commonly used BOLD functional imaging are reviewed. © 2003 Wiley Periodicals, Inc. Concepts Magn Reson 16A: 16,27, 2003 [source]

Effect of cilnidipine vs losartan on cerebral blood flow in hypertensive patients with a history of ischemic stroke: a randomized controlled trial

ACTA NEUROLOGICA SCANDINAVICA, Issue 1 2010
K.-S. Hong
Objectives,,, The aim of this study was to compare the effects of antihypertensive agents on cerebral blood flow (CBF) in hypertensive patients with previous ischemic stroke. Materials and methods,,, In this double-blind, multi-center, non-inferiority trial, 196 patients were randomized to cilnidipine 10,20 mg or losartan 50,100 mg once daily for 4 weeks. Baseline and follow-up CBF as measured by single photon emission computed tomography were obtained in 167. The primary endpoint was the global CBF change. The secondary endpoints were the CBF change in the hemisphere ipsilateral to the index stroke, non-impairment of global CBF and blood pressure (BP) reduction. Results,,, Global CBF increased significantly in the cilnidipine arm (9.0 ± 29.6%, P = 0.0071) and the losartan arm (11.4 ± 31.4%, P = 0.0012), and these changes were not different between the two groups (P = 0.607). However, the estimated difference in percentage global CBF change between the two groups was ,2.43% (97.5% CI, ,13.06% to 8.21%), which crossed the predetermined non-inferiority margin of ,8.6%. Ipsilesional hemispheric CBF change, non-impairment of global CBF and BP reduction were similar in the two groups. Conclusions,,, This trial failed to prove the non-inferiority of cilnidipine to losartan regarding global CBF change. Both the treatments, however, increase the global CBF despite BP lowering. [source]

Brain Blood-flow Alterations Induced by Therapeutic Vagus Nerve Stimulation in Partial Epilepsy: II.

EPILEPSIA, Issue 9 2004
Low Levels of Stimulation, Prolonged Effects at High
Summary:,Purpose: To measure vagus nerve stimulation (VNS)-induced cerebral blood flow (CBF) effects after prolonged VNS and to compare these effects with immediate VNS effects on CBF. Methods: Ten consenting partial epilepsy patients had positron emission tomography (PET) with intravenous [15O]H2O. Each had three control scans without VNS and three scans during 30 s of VNS, within 20 h after VNS began (immediate-effect study), and repeated after 3 months of VNS (prolonged study). After intrasubject subtraction of control from stimulation scans, images were anatomically transformed for intersubject averaging and superimposed on magnetic resonance imaging (MRI) for anatomic localization. Changes on t-statistical maps were considered significant at p < 0.05 (corrected for multiple comparisons). Results: During prolonged studies, CBF changes were not observed in any regions that did not have CBF changes during immediate-effect studies. During both types of studies, VNS-induced CBF increases were similarly located in the bilateral thalami, hypothalami, inferior cerebellar hemispheres, and right postcentral gyrus. During immediate-effect studies, VNS decreased bilateral hippocampal, amygdalar, and cingulate CBF and increased bilateral insular CBF; no significant CBF changes were observed in these regions during prolonged studies. Mean seizure frequency decreased by 25% over a 3-month period between immediate and prolonged PET studies, compared with 3 months before VNS began. Conclusions: Seizure control improved during a period over which some immediate VNS-induced CBF changes declined (mainly over cortical regions), whereas other VNS-induced CBF changes persisted (mainly over subcortical regions). Altered synaptic activities at sites of persisting VNS-induced CBF changes may reflect antiseizure actions. [source]