scholarly journals Effect of Tissue Heterogeneity on the Measurement of Cerebral Blood Flow with the Equilibrium C15O2 Inhalation Technique

1983 ◽  
Vol 3 (4) ◽  
pp. 407-415 ◽  
Author(s):  
Peter Herscovitch ◽  
Marcus E. Raichle
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
White Matter ◽  
Partition Coefficient ◽  
Region Of Interest ◽  
Compartment Model ◽  
Cortical Activation ◽  
Surrounding Tissue ◽  
Inhalation Technique ◽  
Local Flow

The equilibrium C15O2 inhalation method for measuring cerebral blood flow with positron emission tomography (PET) is based on a one-compartment model for which it is assumed that the local flow and partition coefficient are uniform in the tissue region in which flow is to be determined. However, because of the limited spatial resolution of PET, a region of interest will contain a mixture of gray and white matter. We used a computer simulation to examine the effect of this heterogeneity on flow measurement in both normal and pathological states. With gray and white matter flows of 0.80 and 0.20 ml/min/g, respectively, flow is underestimated by a maximum of 20% in a region that is 30% gray. Errors occur not only because of flow heterogeneity, but also because of heterogeneity of partition coefficient and the sensitivity of the method to errors in partition coefficient. Larger errors occur in the case of cerebral hyperemia, although the method becomes more accurate with ischemia. In the case of simulated brain tumor, the accuracy of flow determination varies considerably, depending on the flow and partition coefficient of the tumor and of the surrounding tissue. Finally, incremental changes in gray matter flow, as would occur with functional cortical activation, are not well reflected. Thus, the equilibrium C15O2 inhalation method is limited in its ability to accurately quantitate local cerebral blood flow in heterogeneous tissue regions.

scholarly journals Effects of Xenon Anesthesia on Cerebral Blood Flow in Humans

2007 ◽  
Vol 106 (6) ◽  
pp. 1128-1133 ◽  
Author(s):  
Ruut M. Laitio ◽  
Kaike K. Kaisti ◽  
Jaakko W. Låangsjö ◽  
Sargo Aalto ◽  
Elina Salmi ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
White Matter ◽  
Animal Studies ◽  
Region Of Interest ◽  
Arterial Blood ◽  
Xenon Concentration ◽  
Cerebral Pathology ◽  
The Mean ◽  
Male Subjects

Background Animal studies have demonstrated a strong neuroprotective property of xenon. Its usefulness in patients with cerebral pathology could be compromised by deleterious effects on regional cerebral blood flow (rCBF). Methods 15O-labeled water was used to determine rCBF in nine healthy male subjects at baseline and during 1 minimum alveolar concentration (MAC) of xenon (63%). Anesthesia was based solely on xenon. Absolute changes in rCBF were quantified using region-of-interest analysis and voxel-based analysis. Results Mean arterial blood pressure and arterial partial pressure for carbon dioxide remained unchanged. The mean (+/-SD) xenon concentration during anesthesia was 65.2+/-2.3%. Xenon anesthesia decreased absolute rCBF by 34.7+/-9.8% in the cerebellum (P<0.001), by 22.8+/-10.4% in the thalamus (P=0.001), and by 16.2+/-6.2% in the parietal cortex (P<0.001). On average, xenon anesthesia decreased absolute rCBF by 11.2+/-8.6% in the gray matter (P=0.008). A 22.1+/-13.6% increase in rCBF was detected in the white matter (P=0.001). Whole-brain voxel-based analysis revealed widespread cortical reductions and increases in rCBF in the precentral and postcentral gyri. Conclusions One MAC of xenon decreased rCBF in several areas studied. The greatest decreases were detected in the cerebellum, the thalamus and the cortical areas. Increases in rCBF were observed in the white matter and in the pre- and postcentral gyri. These results are in clear contradiction with ketamine, another N-methyl-D-aspartate antagonist and neuroprotectant, which induces a general increase in cerebral blood flow at anesthetic concentrations.

scholarly journals Coupling between cerebral blood flow and cerebral blood volume: Contributions of different vascular compartments

2018 ◽  
Author(s):  
Roman Wesolowski ◽  
Nicholas P. Blockley ◽  
Ian D. Driver ◽  
Susan T. Francis ◽  
Penny A. Gowland
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Blood Volume ◽  
Cerebral Blood Volume ◽  
Venous Blood ◽  
Region Of Interest ◽  
Compartment Model ◽  
Neural Activation ◽  
Bold Response ◽  
Coupling Constant

AbstractA better understanding of the coupling between changes in cerebral blood flow (CBF) and cerebral blood volume (CBV) is vital for furthering our understanding of the BOLD response. The aim of this study was to measure CBF-CBV coupling in different vascular compartments during neural activation. Three haemodynamic parameters were measured during a visual stimulus. Look-Locker Flow-sensitive Alternating Inversion Recovery (LL-FAIR) was used to measure changes in CBF and arterial CBV (CBVa) using sequence parameters optimised for each contrast. Changes in total CBV (CBVtot) were measured using a Gadolinium based contrast agent technique. Haemodynamic changes were extracted from a region of interest based on voxels that were activated in the CBF experiments. The CBF-CBVtot coupling constant αtot was measured as 0.16±0.14 and the CBF-CBVa coupling constant αa was measured as 0.65±0.24. Using a two compartment model of the vasculature (arterial and venous), the change in venous CBV (CBVv) was predicted for an assumed value of baseline arterial and venous blood volume. These results will enhance the accuracy and reliability of applications that rely on models of the BOLD response, such as calibrated BOLD.

scholarly journals Multiple Factors Involved in the Pathogenesis of White Matter Lesions

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Jing Lin ◽  
Dilong Wang ◽  
Linfang Lan ◽  
Yuhua Fan
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
White Matter ◽  
Genetic Factors ◽  
Subsequent Development ◽  
White Matter Lesions ◽  
Blood Brain Barrier Disruption ◽  
Fluid Attenuated Inversion Recovery ◽  
Cerebral Blood Flow Autoregulation ◽  
Brain Barrier Disruption

White matter lesions (WMLs), also known as leukoaraiosis (LA) or white matter hyperintensities (WMHs), are characterized mainly by hyperintensities on T2-weighted or fluid-attenuated inversion recovery (FLAIR) images. With the aging of the population and the development of imaging technology, the morbidity and diagnostic rates of WMLs are increasing annually. WMLs are not a benign process. They clinically manifest as cognitive decline and the subsequent development of dementia. Although WMLs are important, their pathogenesis is still unclear. This review elaborates on the advances in the understanding of the pathogenesis of WMLs, focusing on anatomy, cerebral blood flow autoregulation, venous collagenosis, blood brain barrier disruption, and genetic factors. In particular, the attribution of WMLs to chronic ischemia secondary to venous collagenosis and cerebral blood flow autoregulation disruption seems reasonable. With the development of gene technology, the effect of genetic factors on the pathogenesis of WMLs is gaining gradual attention.

scholarly journals Trial of remote ischaemic preconditioning in vascular cognitive impairment (TRIC-VCI): protocol

BMJ Open ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. e040466
Author(s):  
Aravind Ganesh ◽  
Philip Barber ◽  
Sandra E Black ◽  
Dale Corbett ◽  
Thalia S Field ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Cognitive Impairment ◽  
White Matter ◽  
Diffusion Tensor ◽  
Vascular Cognitive Impairment ◽  
White Matter Injury ◽  
White Matter Hyperintensity ◽  
Limb Ischaemia ◽  
Ischaemic Brain

IntroductionCerebral small vessel disease (cSVD) accounts for 20%–25% of strokes and is the most common cause of vascular cognitive impairment (VCI). In an animal VCI model, inducing brief periods of limb ischaemia-reperfusion reduces subsequent ischaemic brain injury with remote and local protective effects, with hindlimb remote ischaemic conditioning (RIC) improving cerebral blood flow, decreasing white-matter injury and improving cognition. Small human trials suggest RIC is safe and may prevent recurrent strokes. It remains unclear what doses of chronic daily RIC are tolerable and safe, whether effects persist after treatment cessation, and what parameters are optimal for treatment response.Methods and analysisThis prospective, open-label, randomised controlled trial (RCT) with blinded end point assessment and run-in period, will recruit 24 participants, randomised to one of two RIC intensity groups: one arm treated once daily or one arm twice daily for 30 consecutive days. RIC will consistent of 4 cycles of blood pressure cuff inflation to 200 mm Hg for 5 min followed by 5 min deflation (total 35 min). Selection criteria include: age 60–85 years, evidence of cSVD on brain CT/MRI, Montreal Cognitive Assessment (MoCA) score 13–24 and preserved basic activities of living. Outcomes will be assessed at 30 days and 90 days (60 days after ceasing treatment). The primary outcome is adherence (completing ≥80% of sessions). Secondary safety/tolerability outcomes include the per cent of sessions completed and pain/discomfort scores from patient diaries. Efficacy outcomes include changes in cerebral blood flow (per arterial spin-label MRI), white-matter hyperintensity volume, diffusion tensor imaging, MoCA and Trail-Making tests.Ethics and disseminationResearch Ethics Board approval has been obtained. The results will provide information on feasibility, dose, adherence, tolerability and outcome measures that will help design a phase IIb RCT of RIC, with the potential to prevent VCI. Results will be disseminated through peer-reviewed publications, organisations and meetings.Trial registration numberNCT04109963.

Abstract T P178: Cerebral Blood Flow and Metabolism Associated with Cerebral Microbleeds in Patients with Non-cardioembolic Stroke Without Major Cerebral Arterial Stenosis

Stroke ◽  
2015 ◽  
Vol 46 (suppl_1) ◽  
Author(s):  
Tetsuya Hashimoto ◽  
Chiaki Yokota ◽  
Ryo Shimomura ◽  
Kazuhiro Koshino ◽  
Toshiyuki Uehara ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
White Matter ◽  
Cerebral Blood Volume ◽  
Cerebral Microbleeds ◽  
Cardioembolic Stroke ◽  
Arterial Stenosis ◽  
Oxygen Extraction Fraction ◽  
Group I ◽  
Group Ii

Background and Purpose: Cerebral microbleeds (CMBs) are associated with not only higher age but also extensive white matter lesions (WMLs), indicating that CMBs could be a reflection of microangiopathy. CMBs have not yet been examined in association with cerebral blood flow (CBF) and metabolism. The purpose of this study was to clarify the relationships of CMBs with WMLs volume, and CBF and metabolism in patients with ischemic stroke. Methods: We enrolled 19 patients who had past history of non-cardioembolic stroke without severe stenosis (>50%) in major cerebral arteries (69±7 years, 9 women). We measured WMLs volume and counted the number of CMBs on a 1.5-T magnetic resonance imaging (MRI) scanner. CBF, cerebral blood volume, oxygen extraction fraction and cerebral metabolic rate of oxygen were measured with 15 O-labeled gas positron emission tomography (PET). We set 36 regions of interest (ROIs) in the cortex-subcortex regions, basal ganglia and centra semiovale in each patient on MRI. MRI was superimposed on PET images and 4 parameters of each ROI were calculated. Results: CMBs existed in 14 out of 19 patients (median 5; range 0-39). Patients were divided into 2 groups according to the number of CMBs; less than 5 as the group I (n=9) and 5 or more as the group II (n=10). WMLs volume of the group II was larger than that of the group I (median 38.4 with range of 25.1-91.5 vs. 10.0 with 4.2-73.4 ml, p=0.020). In the centra semiovale, CBF of the group II was significantly lower than that of the group I (12.5±2.5 vs. 15.7±3.5 ml/100g/min, p=0.031). In the other regions, there were no significant differences in all 4 parameters of PET between the 2 groups. Conclusions: We showed that the increases in the number of CMBs could indicate cerebral ischemia in the deep white matter of patients with non-cardioembolic stroke without major cerebral arterial stenosis.

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