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Zarrinkoob, L., Ambarki, K., Wahlin, A., Birgander, R., Eklund, A. & Malm, J. (2015). Blood flow distribution in cerebral arteries. Journal of Cerebral Blood Flow and Metabolism, 35(4), 648-654
Open this publication in new window or tab >>Blood flow distribution in cerebral arteries
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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.

Keyword
aging, cerebral blood flow, circle of Willis, cognitive impairment, phase-contrast MRI, stroke
National Category
Clinical Medicine
Identifiers
urn:nbn:se:umu:diva-103545 (URN)10.1038/jcbfm.2014.241 (DOI)000352027900015 ()25564234 (PubMedID)
Available from: 2015-05-25 Created: 2015-05-21 Last updated: 2018-03-15Bibliographically approved
Malm, J. (2015). Improving research and care for patients with idiopathic NPH. Lancet Neurology, 14(6), 561-563
Open this publication in new window or tab >>Improving research and care for patients with idiopathic NPH
2015 (English)In: Lancet Neurology, ISSN 1474-4422, E-ISSN 1474-4465, Vol. 14, no 6, p. 561-563Article in journal, Editorial material (Other academic) Published
National Category
Neurology
Identifiers
urn:nbn:se:umu:diva-106123 (URN)10.1016/S1474-4422(15)00055-1 (DOI)000354829900003 ()25934243 (PubMedID)
Available from: 2015-07-14 Created: 2015-07-09 Last updated: 2017-12-04Bibliographically approved
Farahmand, D., Qvarlander, S., Malm, J., Wikkelsö, C., Eklund, A. & Tisell, M. (2015). Intracranial pressure in hydrocephalus: impact of shunt adjustments and body positions. Journal of Neurology, Neurosurgery and Psychiatry, 86(2), 222-228
Open this publication in new window or tab >>Intracranial pressure in hydrocephalus: impact of shunt adjustments and body positions
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2015 (English)In: Journal of Neurology, Neurosurgery and Psychiatry, ISSN 0022-3050, E-ISSN 1468-330X, Vol. 86, no 2, p. 222-228Article in journal (Refereed) Published
Abstract [en]

Background The association between intracranial pressure (ICP) and different shunt valve opening pressures in relation to body positions is fundamental for understanding the physiological function of the shunt.

Objective To analyse the ICP and ICP wave amplitude (AMP) at different shunt settings and body positions in patients with hydrocephalus.

Methods In this prospective study 15 patients with communicating hydrocephalus were implanted with a ligated adjustable ventriculoperitoneal shunt. They also received a portable intraparenchymatous ICP-monitoring device. Postoperative ICP and AMP were recorded with the patients in three different body positions (supine, sitting and walking) and with the shunt ligated and open at high, medium and low valve settings. In each patient 12 10 min segments were coded, blinded and analysed for mean ICP and mean AMP using an automated computer algorithm.

Results Mean ICP and mean AMP were lower at all three valve settings compared with the ligated shunt state (p<0.001). Overall, when compared with the supine position, mean ICP was 11.5 +/- 1.1 (mean +/- SD) mm Hg lower when sitting and 10.5 +/- 1.1 mm Hg lower when walking (p<0.001). Mean ICP was overall 1.1 mm Hg higher (p=0.042) when walking compared with sitting. The maximal adjustability difference (highest vs lowest valve setting) was 4.4 mm Hg.

Conclusions Changing from a supine to an upright position reduced ICP while AMP only increased at trend level. Lowering of the shunt valve opening pressure decreased ICP and AMP but the difference in mean ICP in vivo between the highest and lowest opening pressures was less than half that previously observed in vitro.

National Category
Surgery Neurology Other Medical Engineering
Identifiers
urn:nbn:se:umu:diva-101344 (URN)10.1136/jnnp-2014-307873 (DOI)000349720700018 ()24963125 (PubMedID)
Available from: 2015-03-27 Created: 2015-03-27 Last updated: 2017-12-04Bibliographically approved
Ambarki, K., Petr, J., Wahlin, A., Wirestam, R., Zarrinkoob, L., Malm, J. & Eklund, A. (2015). Partial Volume Correction of Cerebral Perfusion Estimates Obtained by Arterial Spin Labeling. In: 16th Nordic-Baltic Conference on Biomedical Engineering: 16. NBC & 10. MTD 2014 joint conferences. October 14-16, 2014, Gothenburg, Sweden. Paper presented at 16th Nordic-Baltic Conference on Biomedical Engineering, October 14-16, 2014, Gothenburg, Sweden (pp. 17-19). , 48
Open this publication in new window or tab >>Partial Volume Correction of Cerebral Perfusion Estimates Obtained by Arterial Spin Labeling
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2015 (English)In: 16th Nordic-Baltic Conference on Biomedical Engineering: 16. NBC & 10. MTD 2014 joint conferences. October 14-16, 2014, Gothenburg, Sweden, 2015, Vol. 48, p. 17-19Conference paper, Published paper (Refereed)
Abstract [en]

Arterial Spin labeling (ASL) is a fully non-invasive MRI method capable to quantify cerebral perfusion. However, gray (GM) and white matter (WM) ASL perfusions are difficult to assess separately due to limited spatial resolution increasing the partial volume effects (PVE). In the present study, ASL PVE correction was implemented based on a regression algorithm in 22 healthy young men. PVE corrected perfusion of GM and WM were compared to previous studies. PVE-corrected GM perfusion was in agreement with literature values. In general, WM perfusion was higher despite the use of PVE correction.

Series
IFMBE Proceedings, ISSN 1680-0737 ; 48
Keyword
MRI, cerebral perfusion, gray and white matter, arterial spin labeling and healthy
National Category
Neurosciences
Identifiers
urn:nbn:se:umu:diva-100142 (URN)10.1007/978-3-319-12967-9_5 (DOI)000347893000005 ()978-3-319-12966-2 (ISBN)978-3-319-12967-9 (ISBN)
Conference
16th Nordic-Baltic Conference on Biomedical Engineering, October 14-16, 2014, Gothenburg, Sweden
Available from: 2015-02-26 Created: 2015-02-24 Last updated: 2018-01-11Bibliographically approved
Dunås, T., Wåhlin, A., Zarrinkoob, L., Ambarki, K., Malm, J. & Eklund, A. (2015). Towards Automatic Identification of Cerebral Arteries in 4D Flow MRI. In: Henrik Mindedal, Mikael Persson (Ed.), 16th Nordic-Baltic Conference on Biomedical Engineering: . Paper presented at 16th Nordic-Baltic Conference on Biomedical Engineering, October 14-16, 2014, Gothenburg, Sweden (pp. 40-43). , 48
Open this publication in new window or tab >>Towards Automatic Identification of Cerebral Arteries in 4D Flow MRI
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2015 (English)In: 16th Nordic-Baltic Conference on Biomedical Engineering / [ed] Henrik Mindedal, Mikael Persson, 2015, Vol. 48, p. 40-43Conference paper, Published paper (Refereed)
Abstract [en]

4D flow MRI is a powerful imaging technique which provides an angiographic image with information about blood flow in a large volume, time resolved over the cardiac cycle, in a short imaging time. This study aims to develop an automatic method for identification of cerebral arteries. The proposed method is based on an atlas of twelve arteries, developed from 4D flow MRI of 25 subjects. The atlas was constructed by normalizing all images to MNI-space, manually identifying the arteries and creating an average over the volume. The identification is done by extracting a vascular skeleton from the image, transforming it to MNI-space, labeling it with the atlas and transforming it back to subject space. The method was evaluated on a pilot cohort of 8 subjects. The rate of correctly identified arteries was 97%.

Series
IFMBE Proceedings, ISSN 1680-0737 ; 48
Keyword
Cerebral arteries, automatic labeling, 4D flow MRI, cerebrovascular atlas
National Category
Neurosciences
Identifiers
urn:nbn:se:umu:diva-100149 (URN)10.1007/978-3-319-12967-9_11 (DOI)000347893000011 ()978-3-319-12966-2 (ISBN)978-3-319-12967-9 (ISBN)
Conference
16th Nordic-Baltic Conference on Biomedical Engineering, October 14-16, 2014, Gothenburg, Sweden
Available from: 2015-02-26 Created: 2015-02-24 Last updated: 2018-01-11Bibliographically approved
Johansson, S. B., Eklund, A., Malm, J., Stemme, G. & Roxhed, N. (2014). A MEMS-based passive hydrocephalus shunt for body position controlled intracranial pressure regulation. Biomedical microdevices (Print), 16(4), 529-536
Open this publication in new window or tab >>A MEMS-based passive hydrocephalus shunt for body position controlled intracranial pressure regulation
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2014 (English)In: Biomedical microdevices (Print), ISSN 1387-2176, E-ISSN 1572-8781, Vol. 16, no 4, p. 529-536Article in journal (Refereed) Published
Abstract [en]

This paper reports a novel micro electro mechanical system (MEMS) valve with posture controlled flow characteristics for improved treatment of hydrocephalus, a disease that is characterized by elevated pressure in the cerebrospinal fluid (CSF) that surrounds the brain and spinal cord. In contrast to conventional differential pressure CSF valves, the CSF valve presented here features a third port which utilizes hydrostatic pressure from a pressure compensating catheter to adapt CSF drainage to optimized levels irrespective of body position. Prototypes have been fabricated using standard MEMS manufacturing processes and the experimental evaluation successfully showed that the flow rate was adjustable with a varying hydrostatic pressure on the third port. Measured data showed that flow rate was at near ideal values at laying body position and that the flow rate can be adjusted to optimal values at standing body position by selecting an appropriate length of the pressure compensating catheter. This is the first pressure balanced CSF valve intended for body position controlled CSF pressure regulation.

Place, publisher, year, edition, pages
Springer Netherlands, 2014
Keyword
MEMS, Hydrocephalus, Cerebrospinal fluid (CSF), Normal pressure, Micro fluidic valve, Passive pressure balancing
National Category
Biomedical Laboratory Science/Technology Nano Technology
Identifiers
urn:nbn:se:umu:diva-91817 (URN)10.1007/s10544-014-9855-3 (DOI)000339112600004 ()
Available from: 2014-09-01 Created: 2014-08-18 Last updated: 2017-12-05Bibliographically approved
Qvarlander, S., Malm, J. & Eklund, A. (2014). CSF dynamic analysis of a predictive pulsatility-based infusion test for normal pressure hydrocephalus. Medical and Biological Engineering and Computing, 52(1), 75-85
Open this publication in new window or tab >>CSF dynamic analysis of a predictive pulsatility-based infusion test for normal pressure hydrocephalus
2014 (English)In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 52, no 1, p. 75-85Article in journal (Refereed) Published
Abstract [en]

Disturbed cerebrospinal fluid (CSF) dynamics are part of the pathophysiology of normal pressure hydrocephalus (NPH) and can be modified and treated with shunt surgery. This study investigated the contribution of established CSF dynamic parameters to AMPmean, a prognostic variable defined as mean amplitude of cardiac-related intracranial pressure pulsations during 10 min of lumbar constant infusion, with the aim of clarifying the physiological interpretation of the variable. AMPmean and CSF dynamic parameters were determined from infusion tests performed on 18 patients with suspected NPH. Using a mathematical model of CSF dynamics, an expression for AMPmean was derived and the influence of the different parameters was assessed. There was high correlation between modelled and measured AMPmean (r = 0.98, p < 0.01). Outflow resistance and three parameters relating to compliance were identified from the model. Correlation analysis of patient data confirmed the effect of the parameters on AMPmean (Spearman's ρ = 0.58-0.88, p < 0.05). Simulated variations of ±1 standard deviation (SD) of the parameters resulted in AMPmean changes of 0.6-2.9 SD, with the elastance coefficient showing the strongest influence. Parameters relating to compliance showed the largest contribution to AMPmean, which supports the importance of the compliance aspect of CSF dynamics for the understanding of the pathophysiology of NPH.

Keyword
Cerebrospinal fluid dynamics, Prognostic tests, Intracranial pressure, Normal pressure hydrocephalus
National Category
Medical Engineering
Identifiers
urn:nbn:se:umu:diva-82750 (URN)10.1007/s11517-013-1110-1 (DOI)000329663200008 ()24151060 (PubMedID)
Available from: 2013-11-08 Created: 2013-11-08 Last updated: 2018-02-12Bibliographically approved
Wåhlin, A., Ambarki, K., Birgander, R., Malm, J. & Eklund, A. (2014). Intracranial pulsatility is associated with regional brain volume in elderly individuals. Neurobiology of Aging, 35(2), 365-372
Open this publication in new window or tab >>Intracranial pulsatility is associated with regional brain volume in elderly individuals
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2014 (English)In: Neurobiology of Aging, ISSN 0197-4580, E-ISSN 1558-1497, Vol. 35, no 2, p. 365-372Article in journal (Refereed) Published
Abstract [en]

Excessive intracranial pulsatility is thought to damage the cerebral microcirculation, causing cognitive decline in elderly individuals. We investigated relationships between brain structure and measures related to intracranial pulsatility among healthy elderly. Thirty-seven stroke-free, non-demented individuals (62-82 years of age) were included. We assessed brain structure, invasively measured cerebrospinal fluid (CSF) pulse pressure, and magnetic resonance-quantified arterial and CSF flow pulsatility, as well as arterial pulse pressure. Using both multivariate partial least squares and ordinary regression analyses, we identified a significant pattern of negative relationships between the volume of several brain regions and measures of intracranial pulsatility. The strongest relationships concerned the temporal lobe cortex and hippocampus. These findings were also coherent with observations of positive relationships between intracranial pulsatility and ventricular volume. In conclusion, elderly subjects with high intracranial pulsatility display smaller brain volume and larger ventricles, supporting the notion that excessive cerebral arterial pulsatility harms the brain. This calls for research investigating altered intracranial cardiac-related pulsatile stress as a potential risk factor that may cause or worsen the prognosis in subjects developing cognitive impairment and dementia.

National Category
Neurology
Identifiers
urn:nbn:se:umu:diva-98388 (URN)10.1016/j.neurobiolaging.2013.08.026 (DOI)000328655600011 ()24080175 (PubMedID)
Available from: 2015-01-21 Created: 2015-01-21 Last updated: 2017-12-05Bibliographically approved
Behrens, A., Lenfeldt, N., Qvarlander, S., Koskinen, L.-O., Malm, J. & Eklund, A. (2013). Are intracranial pressure wave amplitudes measurable through lumbar puncture?. Acta Neurologica Scandinavica, 127(4), 233-241
Open this publication in new window or tab >>Are intracranial pressure wave amplitudes measurable through lumbar puncture?
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2013 (English)In: Acta Neurologica Scandinavica, ISSN 0001-6314, E-ISSN 1600-0404, Vol. 127, no 4, p. 233-241Article in journal (Refereed) Published
Abstract [en]

 Objective The aim of this study was to investigate whether pulsations measured in the brain correspond to those measured in lumbar space, and subsequently whether lumbar punctures could replace invasive recordings. Methods In ten patients with normal pressure hydrocephalus, simultaneous recordings of the intracranial pressure (ICP; intraparenchymal) and lumbar pressure (LP; cerebrospinal fluid pressure) were performed. During registration, pressure was altered between resting pressure and 45mmHg using an infusion test. Data were analyzed regarding pulsations (i.e., amplitudes). Also, the pressure sensors were compared in a bench test. Results The correlation between intracranial and lumbar amplitudes was 0.98. At resting pressure, and moderately elevated ICP, intracranial pulse amplitudes exceeded that of lumbar space with about 0.9mmHg. At the highest ICP, the difference changed to 0.2mmHg. The bench test showed that the agreement of sensor readings was good at resting pressure, but reduced at higher amplitudes. Conclusions Compared to intracranial registrations, amplitudes measured through lumbar puncture were slightly attenuated. The bench test showed that differences were not attributable to dissimilarities of the sensor systems. A lumbar pressure amplitude measurement is an alternative to ICP recording, but the thresholds for what should be interpreted as elevated amplitudes need to be adjusted.

Keyword
intracranial pressure, spinal puncture, cerebrospinal fluid pressure, hydrocephalus, normal pressure, pulse pressure waves
National Category
Neurology
Identifiers
urn:nbn:se:umu:diva-68250 (URN)10.1111/j.1600-0404.2012.01701.x (DOI)000316215900004 ()
Available from: 2013-04-18 Created: 2013-04-15 Last updated: 2017-12-06Bibliographically approved
Ambarki, K., Hallberg, P., Jóhannesson, G., Lindén, C., Zarrinkoob, L., Wåhlin, A., . . . Eklund, A. (2013). Blood flow of ophthalmic artery in healthy individuals determined by phase-contrast magnetic resonance imaging. Investigative Ophthalmology and Visual Science, 54(4), 2738-2745
Open this publication in new window or tab >>Blood flow of ophthalmic artery in healthy individuals determined by phase-contrast magnetic resonance imaging
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2013 (English)In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 54, no 4, p. 2738-2745Article in journal (Refereed) Published
Abstract [en]

PURPOSE: Recent development of magnetic resonance imaging (MRI) offers new possibilities to assess ocular blood flow. This prospective study evaluates the feasibility of phase-contrast MRI (PCMRI) to measure flow rate in the ophthalmic artery (OA) and establish reference values in healthy young (HY) and elderly (HE) subjects.

METHODS: Fifty HY subjects (28 females, 21-30 years of age) and 44 HE (23 females, 64-80 years of age) were scanned on a 3-Tesla MR system. The PCMRI sequence had a spatial resolution of 0.35 mm per pixel, with the measurement plan placed perpendicularly to the OA. Mean flow rate (Qmean), resistive index (RI), and arterial volume pulsatility of OA (ΔVmax) were measured from the flow rate curve. Accuracy of PCMRI measures was investigated using a vessel-phantom mimicking the diameter and the flow rate range of the human OA.

RESULTS: Flow rate could be assessed in 97% of the OAs. Phantom investigations showed good agreement between the reference and PCMRI measurements with an error of <7%. No statistical difference was found in Qmean between HY and HE individuals (HY: mean ± SD = 10.37 ± 4.45 mL/min; HE: 10.81 ± 5.15 mL/min, P = 0.655). The mean of ΔVmax (HY: 18.70 ± 7.24 μL; HE: 26.27 ± 12.59 μL, P < 0.001) and RI (HY: 0.62 ± 0.08; HE: 0.67 ± 0.1, P = 0.012) were significantly different between HY and HE.

CONCLUSIONS: This study demonstrated that the flow rate of OA can be quantified using PCMRI. There was an age difference in the pulsatility parameters; however, the mean flow rate appeared independent of age. The primary difference in flow curves between HE and HY was in the relaxation phase of the systolic peak.

Keyword
magnetic resonance imaging, blood flow, ophthalmic artery
National Category
Ophthalmology
Identifiers
urn:nbn:se:umu:diva-73723 (URN)10.1167/iovs.13-11737 (DOI)000319821700039 ()23518769 (PubMedID)
Available from: 2013-06-27 Created: 2013-06-27 Last updated: 2017-12-06Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-6451-1940

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