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Brain Perfusion (brain + perfusion)
Terms modified by Brain Perfusion Selected AbstractsCerebral Hemodynamics Changes During Retrograde Brain Perfusion in DogsJOURNAL OF NEUROIMAGING, Issue 2 2001Alexander Y. Razumovsky PhD ABSTRACT The objective of this study was to examine cerebral hemodynamics changes during hypothermic circulatory arrest (HCA) with and without retrograde cerebral perfusion (RCP). Thirteen colony-bred hound dogs were placed on cardiopulmonary bypass (CPB) and cooled to 18°C. Five dogs underwent 2 hours of HCA without RCP and 8 with RCP. The animals were then rewarmed on CPB until normothermic and weaned. Cerebral blood flow velocity (CBFV) and Gosling Pulsatility Index (PI) in the middle cerebral artery (MCA) were studied using transcranial Doppler (TCD) ultrasound. At baseline and during pre- and postarrest CPB, there was anterograde direction of blood flow in the MCA. During HCA with RCP, there was retrograde direction of blood flow in the MCA. There was no difference in CBFV between pre-, during, and postarrest CPB in the group with RCP; however, there was significantly increased CBFV during postarrest CPB in the group without RCP compared to the dogs with RCP. Later, at 3 hours after postarrest CPB, there was decreased CBFV in all animals accompanied by increased PI (2.4 ± 0.4 and 2.2 ± 0.6 for animals with RCP and without RCP, respectively) and abnormal TCD waveform changes including decreased diastolic compartment and sharp systolic peak. During hypothermic circulatory arrest, RCP provides CBFV in the MCA comparable to MCA CBFV during CPB. HCA dogs without RCP showed immediate hyperemia on reperfusion. The decreased CBFV and increased PI at 1 hour after postarrest CPB could be an indicator of progressive ischemic injury due to the increased intracranial pressure despite the implementation of RCP. [source] Magnesium sulphate treatment decreases blood,brain barrier permeability during acute hypertension in pregnant ratsEXPERIMENTAL PHYSIOLOGY, Issue 2 2008Anna G. Euser Eclampsia is associated with increased blood,brain barrier (BBB) permeability and formation of cerebral oedema. Magnesium sulphate is used to treat eclampsia despite an unclear mechanism of action. This study was to determine the effect of magnesium sulphate on in vivo BBB permeability and formation of cerebral oedema during acute hypertension and on brain aquaporin-4 (AQP4) protein expression. An in vivo model of hypertensive encephalopathy was used in late-pregnant (LP) rats following magnesium sulphate treatment, 270 mg kg,1i.p. injection every 4 h for 24 h. Permeability of the BBB was determined by in situ brain perfusion of Evan's Blue (EB) and sodium fluorescein (NaFl), and dye clearance determined by fluorescence spectrophotometry. Cerebral oedema was determined following acute hypertension by measuring brain water content. The effect of magnesium treatment on AQP4 expression was determined by Western blot analysis. Acute hypertension with autoregulatory breakthrough increased BBB permeability to EB in both brain regions studied (P < 0.05). Magnesium attenuated BBB permeability to EB during acute hypertension by 41% in the posterior cerebrum (P < 0.05) but had no effect in the anterior cerebrum (P > 0.05). Treatment with magnesium did not change NaFl permeability, cerebral oedema formation or AQP4 expression. In summary, BBB permeability to Evan's Blue was increased by acute hypertension in LP rats, and this was attenuated by treatment with magnesium sulphate. The greatest effect on BBB permeability to EB was in the posterior cerebrum, an area particularly susceptible to oedema formation during eclampsia. [source] High transcytosis of melanotransferrin (P97) across the blood,brain barrierJOURNAL OF NEUROCHEMISTRY, Issue 4 2002Michel Demeule Abstract The blood,brain barrier (BBB) performs a neuroprotective function by tightly controlling access to the brain; consequently it also impedes access of proteins as well as pharmacological agents to cerebral tissues. We demonstrate here that recombinant human melanotransferrin (P97) is highly accumulated into the mouse brain following intravenous injection and in situ brain perfusion. Moreover, P97 transcytosis across bovine brain capillary endothelial cell (BBCEC) monolayers is at least 14-fold higher than that of holo-transferrin, with no apparent intra-endothelial degradation. This high transcytosis of P97 was not related to changes in the BBCEC monolayer integrity. In addition, the transendothelial transport of P97 was sensitive to temperature and was both concentration- and conformation-dependent, suggesting that the transport of P97 is due to receptor-mediated endocytosis. In spite of the high degree of sequence identity between P97 and transferrin, a different receptor than the one for transferrin is involved in P97 transendothelial transport. A member of the low-density lipoprotein receptor protein family, likely LRP, seems to be involved in P97 transendothelial transport. The brain accumulation, high rate of P97 transcytosis and its very low level in the blood suggest that P97 could be advantageously employed as a new delivery system to target drugs directly to the brain. [source] Ultrasound Contrast Agents for Brain Perfusion Imaging and Ischemic Stroke TherapyJOURNAL OF NEUROIMAGING, Issue 3 2005Alberto Della Martina PhD ABSTRACT Stroke is one of the major causes of death and disabilities in industrialized countries. Ultrasound imaging is a largely wide spread bedside technique that is easily accessible and valuable in case of emergency but suffers from the fact that the ultrasound wave has to cross the skull for brain imaging. However, ultrasound contrast agents and new contrast-specific imaging modalities have helped to improve the diagnostic quality of transcranial ultrasonography. This review article surveys and discusses the current state of microbubbles technology and the use of contrast-enhanced transcranial ultrasound for the assessment of brain perfusion. Future aspects and expecta tions in contrast agent functionality, such as targeting and drug or gene delivery, acceleration of thrombolysis, and imaging technology, are also discussed. [source] Dynamic NMR spectroscopy of hyperpolarized 129Xe in human brain analyzed by an uptake modelMAGNETIC RESONANCE IN MEDICINE, Issue 4 2004Wolfgang Kilian Abstract Hyperpolarized 129Xe (HpXe) NMR not only holds promise for functional lung imaging, but for measurements of tissue perfusion as well. To investigate human brain perfusion, several time-series of 129Xe MR spectra were recorded from one healthy volunteer after HpXe inhalation. The time-dependent amplitudes of the MR spectra were analyzed by using a compartment model for xenon uptake modified to account for the loss of 129Xe polarization due to RF-excitation and for the breathhold technique used in the experiments. This analysis suggests that the resonances detected at 196.5 ± 1 ppm and 193 ± 1 ppm originate from HpXe dissolved in gray and white matter, respectively, and that T1 relaxation times of HpXe are different in gray and white matter (T1g > T1w). Magn Reson Med 51:843,847, 2004. © 2004 Wiley-Liss, Inc. [source] Theoretical Simulation of Oxygen Transport to Brain by Networks of Microvessels: Effects of Oxygen Supply and Demand on Tissue HypoxiaMICROCIRCULATION, Issue 4 2000T.W. SECOMB ABSTRACT Objective: Simulations of oxygen delivery by a three-dimensional network of microvessels in rat cerebral cortex were used to examine how the distribution of partial pressure of oxygen (PO2) in tissue depends on blood flow and oxygen consumption rates. Methods: Network geometry was deduced from previously published scanning electron micrographs of corrosion casts. A nonlinear least-squares method, using images obtained at three different angles, was used to estimate vessel locations. The network consisted of 50 segments in a region 140 µm × 150 µm × 160 µm. A Green's function method was used to predict the PO2 distribution. Effects of varying perfusion and consumption were examined, relative to a control state with consumption 10 cm3O2/100 g per min and perfusion 160 cm3/100 g per min. Results: In the control state, minimum tissue PO2 was 7 mm Hg. A Krogh-type model with the same density of vessels, but with uniform spacing, predicted a minimum tissue PO2 of 23 mm Hg. For perfusion below 60% of control, tissue hypoxia (PO2 <1 mm Hg) was predicted. When perfusion was reduced by 75%, the resulting hypoxia could be eliminated by a 31% reduction in oxygen consumption rate. Conclusions: The simulations suggest that tissue hypoxia resulting from a severe decrease in brain perfusion, as can occur in stroke, may be avoided by a moderate decrease in oxygen consumption rate. [source] Neural correlates of memory in depression measured by brain perfusion SPECT at restPSYCHIATRY AND CLINICAL NEUROSCIENCES, Issue 5 2009Hideki Azuma md Aim:, Brain metabolism activated studies have indicated associations between memory and the anterior cingulate cortex and hippocampus in patients with depression. The aim of the present study was therefore to investigate memory function, measured as performance on the Wechsler Memory Scale,Revised (WMS-R), and its relationship to brain perfusion using single-photon emission computed tomography (SPECT) at rest in patients with depression. Methods:, The Hamilton Rating Scale for Depression (HAMD) and WMS-R were measured for 17 patients with depression by an independent clinical evaluation team. Voxel-based correlation analyses were performed with statistical parametric mapping at an extent threshold of 200 voxels. Associations were controlled for state and trait factors. Results:, WMS-R measurements of verbal, visual, and general memory were inversely correlated with brain perfusion in the right anterior cingulate cortex, left premotor cortices, and both regions, respectively. The HAMD directly correlated with brain perfusion in the right anterior cingulate cortex. Conclusion:, Brain perfusion SPECT measurements of the anterior cingulate cortex at rest were associated with the severity of depression and immediate memory scores measured with the WMS-R. [source] Relationship between psychiatric symptoms and regional cerebral blood flow in patients with mild Alzheimer's diseasePSYCHOGERIATRICS, Issue 3 2008Keisuke NAKAJIMA Abstract Background:, Behavioral and psychological symptoms of dementia (BPSD) are frequently observed in patients with dementia and often cause serious problems. However, the cause of BPSD has not yet been elucidated. Moreover, the precise evaluation of BPSD in mild dementia has not been studied in any great detail. In the present study, we investigated the relationship between psychiatric symptoms and regional cerebral blood flow (rCBF) in patients with mild Alzheimer's disease (AD). Methods:, The present study included 47 patients (20 men and 27 women) who were diagnosed with mild AD. Mean patient age was 72.8 ± 8.2 years. Single photon emission computed tomography (SPECT) with 99mTc-ethyl cysteinate dimer (99mTc-ECD) was performed in all patients. The SPECT data were analyzed using a three-dimensional stereotactic region of interest template, which evaluated CBF in 24 segments. Psychiatric symptoms were evaluated in patients using the Brief Psychiatric Rating Scale. Each psychiatric symptom was designated as ,symptom present' in cases in which the BPRS item score was more than 3. We compared 10 segments of rCBF in symptom-present patients with those in symptom-absent patients. Results:, Motor retardation was the most common psychiatric symptom (36.2%), followed by depression (19.1%), anxiety (17.0%), emotional withdrawal (17.0%), and somatic concern (14.9%). Alzheimer's disease patients with motor retardation exhibited a tendency towards lower rCBF in seven segments (left callosomarginal, bilateral parietal, bilateral angular, and bilateral temporal). However, no specific tendency was observed in depression, anxiety, and somatic concern. Conclusions:, In the present study, we observed a tendency for decreased brain perfusion in patients with motor retardation. Further studies are necessary to confirm that this trend contributes to the appearance of psychiatric symptoms in patients with mild AD. [source] Microemboli may link spreading depression, migraine aura, and patent foramen ovaleANNALS OF NEUROLOGY, Issue 2 2010Ala Nozari MD Objective Patent foramen ovale and pulmonary arteriovenous shunts are associated with serious complications such as cerebral emboli, stroke, and migraine with aura. The pathophysiological mechanisms that link these conditions are unknown. We aimed to establish a mechanism linking microembolization to migraine aura in an experimental animal model. Methods We introduced particulate or air microemboli into the carotid circulation in mice to determine whether transient microvascular occlusion, insufficient to cause infarcts, triggered cortical spreading depression (CSD), a propagating slow depolarization that underlies migraine aura. Results Air microemboli reliably triggered CSD without causing infarction. Polystyrene microspheres (10,m) or cholesterol crystals (<70,m) triggered CSD in 16 of 28 mice, with 60% of the mice (40% of those with CSD) showing no infarcts or inflammation on detailed histological analysis of serial brain sections. No evidence of injury was detected on magnetic resonance imaging examination (9.4T; T2 weighted) in 14 of 15 selected animals. The occurrence of CSD appeared to be related to the magnitude and duration of flow reduction, with a triggering mechanism that depended on decreased brain perfusion but not sustained tissue damage. Interpretation In a mouse model, microemboli triggered CSD, often without causing microinfarction. Paradoxical embolization then may link cardiac and extracardiac right-to-left shunts to migraine aura. If translatable to humans, a subset of migraine auras may belong to a spectrum of hypoperfusion disorders along with transient ischemic attacks and silent infarcts. ANN NEUROL 2010;67:221,229 [source] Early magnetic resonance imaging findings in patients receiving tissue plasminogen activator predict outcome: Insights into the pathophysiology of acute stroke in the thrombolysis era,ANNALS OF NEUROLOGY, Issue 1 2004Julio A. Chalela MD We measured ischemic brain changes with diffusion and perfusion MRI in 42 ischemic stroke patients before and 2 hours (range approximately 1.5 to 4.5 hours) after standard intravenous tissue plasminogen activator (tPA) therapy. The median time from stroke onset to tPA was 131 minutes. Clinical and MRI variables (change in perfusion and/or diffusion weighted lesion volume) were compared between those with excellent outcome defined as 3-month modified Rankin score (mRS) of 0 to 1 and those with incomplete recovery (mRS >1). In multivariate logististic regression analysis, the most powerful independent predictor for excellent outcome was improved brain perfusion: hypoperfusion volume on mean transit time (MTT) map decrease >30% from baseline to 2-hour post tPA scan (p=0.009; odds ratio [95% confidence interval], 20.7 [2.1-203.9]). Except for age < 70 years, no other baseline clinical or imaging variable was an independent predictor of outcome. We propose MTT lesion volume decrease more than 30% 2 hours after tPA as an early marker of long-term clinical benefit of thrombolytic therapy. [source] Cerebral tissue oxygenation index and superior vena cava blood flow in the very low birth weight infantACTA PAEDIATRICA, Issue 1 2009M Moran Abstract Background: Superior vena cava (SVC) flow assesses blood flow from the upper body, including the brain. Near infrared spectroscopy (NIRS) provides information on brain perfusion and oxygenation. Aim: To assess the relationship between cerebral tissue oxygenation index (cTOI) and cardiac output measures in the very low birth weight (VLBW) infant in the first day of life. Methods: A prospective observational cohort study. Neonates with birth weight less than 1500 g (VLBW) were eligible for enrollment. Newborns with congenital heart disease, major congenital malformations and greater than Papile grade1 Intraventricular Haemorrhage on day 1 of life were excluded. Echocardiographic evaluation of SVC flow was performed in the first 24 h of life. Low SVC flow states were defined as a flow less than 40 mL/kg/min. cTOI was measured using NIRO 200 Hamamatsu. Results: Twenty-seven VLBW neonates had both echocardiography and NIRS performed. The median (range) gestation was 29/40 (25 + 3 to 31 + 5 weeks) and median birth weight was 1.2 kg (0.57,1.48 kg). The mean (SD) TOI was 68.1 (7.9)%. The mean (SD) SVC flow was 70.36(39.5) mLs/kg/min. The correlation coefficient of cerebral tissue oxygenation and SVC flow was r = 0.53, p-value 0.005. There was a poor correlation between right and left ventricular output and cTOI which is not surprising considering the influence of intra- and extracardiac shunts. Conclusion: There is a positive relationship between cerebral TOI values and SVC flow in the very low birth infant on day one of life. [source] | |||||||||||||