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Blood flow distribution in cerebral arteries
Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Clinical Neuroscience.
Umeå University, Faculty of Medicine, Department of Radiation Sciences. Umeå University, Faculty of Science and Technology, Centre for Biomedical Engineering and Physics (CMTF).
Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics. Umeå University, Faculty of Medicine, Umeå Centre for Functional Brain Imaging (UFBI).
Umeå University, Faculty of Medicine, Department of Radiation Sciences.
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2015 (English)In: Journal of Cerebral Blood Flow and Metabolism, ISSN 0271-678X, E-ISSN 1559-7016, Vol. 35, no 4, p. 648-654Article in journal (Refereed) Published
Abstract [en]

High-resolution phase-contrast magnetic resonance imaging can now assess flow in proximal and distal cerebral arteries. The aim of this study was to describe how total cerebral blood flow (tCBF) is distributed into the vascular tree with regard to age, sex and anatomic variations. Forty-nine healthy young (mean 25 years) and 45 elderly (mean 71 years) individuals were included. Blood flow rate (BFR) in 21 intra-and extracerebral arteries was measured. Total cerebral blood flow was defined as BFR in the internal carotid plus vertebral arteries and mean cerebral perfusion as tCBF/brain volume. Carotid/vertebral distribution was 72%/28% and was not related to age, sex, or brain volume. Total cerebral blood flow (717 +/- 123 mL/min) was distributed to each side as follows: middle cerebral artery (MCA), 21%; distal MCA, 6%; anterior cerebral artery (ACA), 12%, distal ACA, 4%; ophthalmic artery, 2%; posterior cerebral artery (PCA), 8%; and 20% to basilar artery. Deviating distributions were observed in subjects with 'fetal' PCA. Blood flow rate in cerebral arteries decreased with increasing age (P < 0.05) but not in extracerebral arteries. Mean cerebral perfusion was higher in women (women: 61 +/- 8; men: 55 +/- 6 mL/min/100 mL, P < 0.001). The study describes a new method to outline the flow profile of the cerebral vascular tree, including reference values, and should be used for grading the collateral flow system.

Place, publisher, year, edition, pages
2015. Vol. 35, no 4, p. 648-654
Keywords [en]
aging, cerebral blood flow, circle of Willis, cognitive impairment, phase-contrast MRI, stroke
National Category
Clinical Medicine
Identifiers
URN: urn:nbn:se:umu:diva-103545DOI: 10.1038/jcbfm.2014.241ISI: 000352027900015PubMedID: 25564234OAI: oai:DiVA.org:umu-103545DiVA, id: diva2:813926
Available from: 2015-05-25 Created: 2015-05-21 Last updated: 2019-05-09Bibliographically approved
In thesis
1. Cerebral blood flow distribution, collateral function and pulsatility in healthy and in patients with symptomatic carotid stenosis : a magnetic resonance imaging approach
Open this publication in new window or tab >>Cerebral blood flow distribution, collateral function and pulsatility in healthy and in patients with symptomatic carotid stenosis : a magnetic resonance imaging approach
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Cerebralt blodflöde med fokus på blodflödesfördelning, kollateraler och artärpulsationer, hos friska och hos patienter med symtomatisk karotisstenos : en tillämpning med magnetisk resonanstomografi
Abstract [en]

Background: For the detection and treatment of early cerebral vascular disease it is of paramount importance to first understand the normal physiology of the cerebral vasculature, and subsequently, to understand how and when pathology can develop from that. This is especially important as the population above 65 years of age is increasing and aging itself is an established risk factor for the development of cerebral vascular disease. This, however, is not always an easy task, since there is a subtle balance and overlap between age-related physiological and pathophysiological changes in the arterial system. Atherosclerotic changes that lead to the development of carotid artery stenosis are responsible for about one fifth of all ischemic strokes. Today, the current state of evidence and the algorithm for carotid revascularization is mainly focused on the degree of carotid stenosis and not on its impact on cerebral hemodynamics. One reason for this is the lack of a non-invasive method, that allows for repeated investigations and provides accurate and reliable results to study cerebral hemodynamic changes. The overall aim of this thesis was to explore and develop a comprehensive approach to investigate the cerebral blood flow distribution, collateral function and pulsatility in healthy subjects and in patients with symptomatic carotid stenosis using a phase-contrast magnetic resonance imaging (PCMRI) platform. The thesis is based on four scientific papers (papers I—IV). 

Methods: In papers I and II, 49 healthy young (mean 25 years) and 45 healthy elderly (mean 71 years) subjects were included. 2D PCMRI was used to assess cerebral blood flow rate (BFR), pulsatility index (PI) and dampening factor (DF) in 15 cerebral arteries and in the ophthalmic arteries (OA). Thirty-eight patients (mean 72 years) with symptomatic carotid stenosis were included in paper III. Nineteen of these patients (mean 71 years) underwent carotid endarterectomy (CEA) (paper IV). 4D PCMRI was used for BFR assessment in papers III and IV. BFR, its distribution and collateral routes, was measured in 17 cerebral arteries and in the OA. The BFR on ipsilateral side (with symptomatic stenosis) was compared to the contralateral side (papers III and IV). BFR laterality was defined as contralateral BFR minus ipsilateral BFR in paired arteries and, BFR was compared before and after CEA (paper IV).

Results: On average, in healthy subjects, 72% of the total cerebral blood flow (tCBF) was distributed through the anterior circulation and 28% through the posterior circulation. The distribution was symmetrical and not affected by age, sex, or brain volume (paper I). Aging resulted in lower BFRs, increased pulsatility and reduced dampening capacity in cerebral arteries. Anatomical variations in the circle of Willis resulted in an asymmetrical distribution of blood flow (papers I and II). In patients with carotid stenosis, a lower BFR was found in the internal carotid artery (ICA) and its branches on the ipsilateral side. The anterior cerebral artery territory was bilaterally, primarily, supplied by the contralateral ICA. In addition to the supply through the ICA, the middle cerebral artery (MCA) territory on the ipsilateral side was secured by collateral supply from the OA and the posterior communicating arteries, seen as retrograde flow in those arteries. Despite these compensations, BFR in ipsilateral side MCA was lower, and this laterality was more pronounced in patients with severe carotid stenosis (≥70%). After CEA, the distribution of BFR going into the cerebral arteries was found to be symmetrically distributed. Total CBF increased postoperatively in patients with collateral recruitment preoperatively (n=9). The BFR laterality in MCA observed prior to CEA, was found only in the group of patients with collateral recruitment preoperatively (paper IV). The degree of stenosis did not differ between the groups with and without collateral recruitment. 

Conclusions: This thesis provides a new and comprehensive approach to mapping and quantifying normal cerebral blood flow and pulsatility. By presenting the distribution of tCBF going into cerebral arteries, instead of using absolute values, the effect of age could be neutralized and the results can be applicable when describing healthy cerebral blood flow, regardless of age. 4D PCMRI made it possible to describe the altered blood flow distribution and collateral ranking in patients with carotid stenosis prior to CEA and its normalization after the procedure. Our findings highlight the importance of BFR quantification for understanding cerebral hemodynamics in patients with carotid stenosis. 4D PCMRI technique is a promising clinical tool for investigations of cerebral hemodynamics in patients with stroke.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2019. p. 63
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 2023
Keywords
Aging, Arterial pulsatility, Carotid stenosis, Cerebral arteries, Cerebral blood flow, Cerebral collateral blood flow, Circle of Willis, Phase contrast magnetic resonance imaging
National Category
Neurology
Identifiers
urn:nbn:se:umu:diva-158834 (URN)978-91-7855-036-4 (ISBN)
Public defence
2019-06-05, Hörsal B, Unod T9, Norrlands universitetssjukhus, Umeå, 13:00 (English)
Opponent
Supervisors
Funder
Swedish Heart Lung Foundation, 20140592Swedish Research Council, 2015-05616
Available from: 2019-05-15 Created: 2019-05-09 Last updated: 2019-05-14Bibliographically approved

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Zarrinkoob, LalehAmbarki, KhalidWåhlin, AndersBirgander, RichardEklund, AndersMalm, Jan

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Zarrinkoob, LalehAmbarki, KhalidWåhlin, AndersBirgander, RichardEklund, AndersMalm, Jan
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