Umeå University's logo

umu.sePublications
Change search
Link to record
Permanent link

Direct link
Publications (10 of 11) Show all publications
Holmgren, M., Henze, A., Wåhlin, A., Eklund, A., Fox, A. J. & Johansson, E. (2024). Phase-contrast magnetic resonance imaging of intracranial and extracranial blood flow in carotid near-occlusion. Neuroradiology, 66(4), 589-599
Open this publication in new window or tab >>Phase-contrast magnetic resonance imaging of intracranial and extracranial blood flow in carotid near-occlusion
Show others...
2024 (English)In: Neuroradiology, ISSN 0028-3940, E-ISSN 1432-1920, Vol. 66, no 4, p. 589-599Article in journal (Refereed) Published
Abstract [en]

Purpose: Compare extracranial internal carotid artery flow rates and intracranial collateral use between conventional ≥ 50% carotid stenosis and carotid near-occlusion, and between symptomatic and asymptomatic carotid near-occlusion.

Methods: We included patients with ≥ 50% carotid stenosis. Degree of stenosis was diagnosed on CTA. Mean blood flow rates were assessed with four-dimensional phase-contrast MRI.

Results: We included 110 patients of which 83% were symptomatic, and 38% had near-occlusion. Near-occlusions had lower mean internal carotid artery flow (70 ml/min) than conventional ≥ 50% stenoses (203 ml/min, P <.001). Definite use of ≥ 1 collateral was found in 83% (35/42) of near-occlusions and 10% (7/68) of conventional stenoses (P <.001). However, there were no differences in total cerebral blood flow (514 ml/min vs. 519 ml/min, P =.78) or ipsilateral hemispheric blood flow (234 vs. 227 ml/min, P =.52), between near-occlusions and conventional ≥ 50% stenoses, based on phase-contrast MRI flow rates. There were no differences in total cerebral or hemispheric blood flow, or collateral use, between symptomatic and asymptomatic near-occlusions.

Conclusion: Near-occlusions have lower internal carotid artery flow rates and more collateral use, but similar total cerebral blood flow and hemispheric blood flow, compared to conventional ≥ 50% carotid stenosis.

Place, publisher, year, edition, pages
Springer Nature, 2024
Keywords
Carotid near-occlusion, Carotid stenosis, Collaterals, CT angiography, Intracerebral flow, Phase-contrast MRI
National Category
Radiology, Nuclear Medicine and Medical Imaging Neurology
Identifiers
urn:nbn:se:umu:diva-221786 (URN)10.1007/s00234-024-03309-y (DOI)001169859900002 ()38400954 (PubMedID)2-s2.0-85185963642 (Scopus ID)
Funder
Knut and Alice Wallenberg FoundationRegion VästerbottenSwedish Heart Lung FoundationThe Swedish Stroke AssociationHarald Jeanssons stiftelseSwedish Society of Medicine
Available from: 2024-03-19 Created: 2024-03-19 Last updated: 2024-03-19Bibliographically approved
Holmgren, M., Henze, A., Wåhlin, A., Eklund, A., Fox, A. J. & Johansson, E. (2023). Diagnostic separation of conventional ⩾50% carotid stenosis and near-occlusion with phase-contrast MRI. European Stroke Journal
Open this publication in new window or tab >>Diagnostic separation of conventional ⩾50% carotid stenosis and near-occlusion with phase-contrast MRI
Show others...
2023 (English)In: European Stroke Journal, ISSN 2396-9873, E-ISSN 2396-9881Article in journal (Refereed) Epub ahead of print
Abstract [en]

Introduction: The aim of this study was to assess sensitivity, specificity and interrater reliability of phase-contrast MRI (PC-MRI) for diagnosing carotid near-occlusion.

Patients and methods: Prospective cross-sectional study conducted between 2018 and 2021. We included participants with suspected 50%–100% carotid stenosis on at least one side, all were examined with CT angiography (CTA) and PC-MRI and both ICAs were analyzed. Degree of stenosis on CTA was the reference test. PC-MRI-based blood flow rates in extracranial ICA and intracranial cerebral arteries were assessed. ICA-cerebral blood flow (CBF) ratio was defined as ICA divided by sum of both ICAs and Basilar artery.

Results: We included 136 participants. The ICAs were 102 < 50% stenosis, 88 conventional ⩾50% stenosis (31 with ⩾70%), 49 near-occlusion, 12 occlusions, 20 unclear cause of small distal ICA on CTA and one excluded. For separation of near-occlusion and conventional stenoses, ICA flow rate and ICA-CBF ratio had the highest area under the curve (AUC; 0.98–0.99) for near-occlusion. ICA-CBF ratio ⩽0.225 was 90% (45/49) sensitive and 99% (188/190) specific for near-occlusion. Inter-rater reliability for this threshold was excellent (kappa 0.98). Specificity was 94% (29/31) for cases with ⩾70% stenosis. PC-MRI had modest performance for separating <50% and conventional ⩾50% stenosis (highest AUC 0.74), and eight (16%) of near-occlusions were not distinguishable from occlusion (no visible flow).

Conclusion: ICA-CBF ratio ⩽0.225 on PC-MRI is an accurate and reliable method to separate conventional ⩾50% stenosis and near-occlusion that is feasible for routine use. PC-MRI should be considered further as a potential standard method for near-occlusion detection, to be used side-by-side with established modalities as PC-MRI cannot separate other degrees of stenosis.

Place, publisher, year, edition, pages
Sage Publications, 2023
Keywords
Carotid stenosis, CT angiography, near-occlusion, phase-contrast MRI
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:umu:diva-217715 (URN)10.1177/23969873231215634 (DOI)001112325800001 ()38032058 (PubMedID)2-s2.0-85178479481 (Scopus ID)
Funder
Knut and Alice Wallenberg FoundationRegion VästerbottenSwedish Heart Lung FoundationThe Swedish Stroke AssociationHarald and Greta Jeansson FoundationThe Swedish Medical AssociationUmeå University
Available from: 2023-12-14 Created: 2023-12-14 Last updated: 2023-12-14
Johansson, E., Holmgren, M., Henze, A. & Fox, A. J. (2022). Diagnosing carotid near-occlusion is a difficult task - but it might get easier. Neuroradiology, 64, 1709-1714
Open this publication in new window or tab >>Diagnosing carotid near-occlusion is a difficult task - but it might get easier
2022 (English)In: Neuroradiology, ISSN 0028-3940, E-ISSN 1432-1920, Vol. 64, p. 1709-1714Article in journal, Editorial material (Other academic) Published
Place, publisher, year, edition, pages
Springer, 2022
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:umu:diva-198307 (URN)10.1007/s00234-022-03007-7 (DOI)000824283500001 ()35829763 (PubMedID)2-s2.0-85134345823 (Scopus ID)
Available from: 2022-07-29 Created: 2022-07-29 Last updated: 2023-03-24Bibliographically approved
Nilsson, D., Holmgren, M., Holmlund, P., Wåhlin, A., Eklund, A., Dahlberg, T., . . . Andersson, M. (2022). Patient-specific brain arteries molded as a flexible phantom model using 3D printed water-soluble resin. Scientific Reports, 12, Article ID 10172.
Open this publication in new window or tab >>Patient-specific brain arteries molded as a flexible phantom model using 3D printed water-soluble resin
Show others...
2022 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 12, article id 10172Article in journal (Refereed) Published
Abstract [en]

Visualizing medical images from patients as physical 3D models (phantom models) have many roles in the medical field, from education to preclinical preparation and clinical research. However, current phantom models are generally generic, expensive, and time-consuming to fabricate. Thus, there is a need for a cost- and time-efficient pipeline from medical imaging to patient-specific phantom models. In this work, we present a method for creating complex 3D sacrificial molds using an off-the-shelf water-soluble resin and a low-cost desktop 3D printer. This enables us to recreate parts of the cerebral arterial tree as a full-scale phantom model (10×6×410×6×4 cm) in transparent silicone rubber (polydimethylsiloxane, PDMS) from computed tomography angiography images (CTA). We analyzed the model with magnetic resonance imaging (MRI) and compared it with the patient data. The results show good agreement and smooth surfaces for the arteries. We also evaluate our method by looking at its capability to reproduce 1 mm channels and sharp corners. We found that round shapes are well reproduced, whereas sharp features show some divergence. Our method can fabricate a patient-specific phantom model with less than 2 h of total labor time and at a low fabrication cost.

Place, publisher, year, edition, pages
Nature Publishing Group, 2022
National Category
Orthopaedics Other Physics Topics Medical Image Processing Other Medical Engineering
Identifiers
urn:nbn:se:umu:diva-195731 (URN)10.1038/s41598-022-14279-7 (DOI)000812565400068 ()2-s2.0-85132118240 (Scopus ID)
Funder
Swedish Research Council, 2019-04016
Available from: 2022-06-03 Created: 2022-06-03 Last updated: 2023-09-05Bibliographically approved
Holmgren, M., Holmlund, P., Stoverud, K.-H., Zarrinkoob, L., Wåhlin, A., Malm, J. & Eklund, A. (2022). Prediction of cerebral perfusion pressure during carotid surgery: A computational fluid dynamics approach. Clinical Biomechanics, 100, Article ID 105827.
Open this publication in new window or tab >>Prediction of cerebral perfusion pressure during carotid surgery: A computational fluid dynamics approach
Show others...
2022 (English)In: Clinical Biomechanics, ISSN 0268-0033, E-ISSN 1879-1271, Vol. 100, article id 105827Article in journal (Refereed) Published
Abstract [en]

Background: Maintaining cerebral perfusion pressure in the brain when a carotid artery is closed during vascular surgery is critical for avoiding intraoperative hypoperfusion and risk of ischemic stroke. Here we propose and evaluate a method based on computational fluid dynamics for predicting patient-specific cerebral perfusion pressures at carotid clamping during carotid endarterectomy.

Methods: The study consisted of 22 patients with symptomatic carotid stenosis who underwent carotid endarterectomy (73 ± 5 years, 59–80 years, 17 men). The geometry of the circle of Willis was obtained preoperatively from computed tomography angiography and corresponding flow rates from four-dimensional flow magnetic resonance imaging. The patients were also classified as having a present or absent ipsilateral posterior communicating artery based on computed tomography angiography. The predicted mean stump pressures from computational fluid dynamics were compared with intraoperatively measured stump pressures from carotid endarterectomy.

Findings: On group level, there was no difference between the predicted and measured stump pressures (−0.5 ± 13 mmHg, P = 0.86) and the pressures were correlated (r = 0.44, P = 0.039). Omitting two outliers, the correlation increased to r = 0.78 (P < 0.001) (−1.4 ± 8.0 mmHg, P = 0.45). Patients with a present ipsilateral posterior communicating artery (n = 8) had a higher measured stump pressure than those with an absent artery (n = 12) (P < 0.001).

Interpretation: The stump pressure agreement indicates that the computational fluid dynamics approach was promising in predicting cerebral perfusion pressures during carotid clamping, which may prove useful in the preoperative planning of vascular interventions.

Keywords
Carotid stenosis, Computational fluid dynamics, Endarterectomy, Ischemic stroke, Magnetic resonance imaging
National Category
Neurology
Identifiers
urn:nbn:se:umu:diva-201362 (URN)10.1016/j.clinbiomech.2022.105827 (DOI)000926947300006 ()2-s2.0-85142357306 (Scopus ID)
Funder
Swedish Research Council, 2015–05616Swedish Research Council, 2017–04949Region VästerbottenSwedish Heart Lung Foundation, 20140592
Available from: 2022-12-05 Created: 2022-12-05 Last updated: 2023-09-05Bibliographically approved
Holmgren, M. (2021). 4D flow MRI and modelling to assess cerebral arterial hemodynamics: method development and evaluation, with implementation in patients with symptomatic carotid stenosis. (Doctoral dissertation). Umeå: Umeå universitet
Open this publication in new window or tab >>4D flow MRI and modelling to assess cerebral arterial hemodynamics: method development and evaluation, with implementation in patients with symptomatic carotid stenosis
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Blood flow measurements are important for understanding the development of cerebrovascular diseases. With 4D flow magnetic resonance imaging (4D flow MRI), simultaneous velocity measurements are obtained in all cerebral arteries in a scan of about ten minutes. However, 4D flow MRI is a relatively new technique. For usefulness in both clinics and research, detailed knowledge is needed about its accuracy and precision for flow quantification. In patients with stroke or transient ischemic attack (TIA) from a symptomatic carotid stenosis, the stenosis may generate a difference in blood pressure and flow between the left and right cerebral hemispheres. Such a hemispheric pressure difference could be an early marker of to what extent a stenosis is affecting cerebral hemodynamics, which could be useful in the planning of carotid surgery. 

The overall aim of the thesis was to determine the accuracy of 4D flow MRI to measure cerebral arterial blood flow, and to develop and evaluate an approach combining 4D flow MRI and computational fluid dynamics (CFD) to characterize the cerebral arterial hemodynamics, with implementation in patients with symptomatic carotid stenosis. The thesis is based on four papers, investigating two cohorts.

The first cohort consisted of 35 elderly volunteers (mean age 79 years) and was studied in paper I-II. Blood flow rates were measured in nine cerebral arteries with 4D flow MRI and 2D phase-contrast MRI as reference. Three different flow quantification methods for 4D flow MRI were evaluated and optimized: one clustering approach and two threshold-based methods. The proposed new method, based on a locally adapted threshold, outperformed the previously suggested methods in flow rate quantification. For the clustering method, flow rates were systematically underestimated. 4D flow MRI was also evaluated to assess different arterial pulsatility measures, and a Windkessel model was used to estimate reference values for cerebrovascular resistance and cerebral arterial compliance in elderly.

The second cohort consisted of 28 stroke and TIA patients (mean age 73 years) with symptomatic carotid stenosis and was studied in paper III-IV. With 4D flow MRI and CFD, the preoperative hemispheric pressure laterality was quantified in the patients. The pressure laterality was compared to hemispheric flow lateralities. Estimating the hemispheric pressure laterality was a promising physiological biomarker for grading the cerebral arterial hemodynamic disturbances in patients with symptomatic carotid stenosis. A CFD model was also developed to predict carotid stump pressure, i.e., the important pressure measured in the clamped carotid artery during surgical removal of the stenosis. The predicted stump pressures were correlated with the pressures measured during surgery. Stump pressure prediction was promising and could be a potential tool in the preoperative planning in order to avoid hypoperfusion during surgery. 

In summary, post-processing methods were successfully developed and evaluated for accurate assessment of mean and pulsatile cerebral blood flow rates with 4D flow MRI. Thereby, this thesis provided knowledge about possibilities and limitations of how 4D flow MRI can be used with respect to cerebral arterial blood flow rate assessment. By contributing with models combining 4D flow MRI and CFD, specifically developed for analysis of pressure distributions in cerebral arteries, novel methods were proposed for assessing patients with symptomatic carotid stenosis in the planning of carotid surgery.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2021. p. 69
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 2128
Keywords
4D flow MRI, carotid stenosis, cerebral blood flow, cerebral arterial compliance, cerebrovascular resistance, circleof Willis, computational fluid dynamics, magnetic resonance imaging, stroke, vascular disease
National Category
Medical Image Processing Neurology
Research subject
Neurology
Identifiers
urn:nbn:se:umu:diva-182250 (URN)978-91-7855-509-3 (ISBN)978-91-7855-510-9 (ISBN)
Public defence
2021-05-12, Betula, Norrlands universitetssjukhus + Zoom, Umeå, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2021-04-21 Created: 2021-04-14 Last updated: 2021-11-01Bibliographically approved
Holmgren, M., Stoverud, K.-H., Zarrinkoob, L., Wåhlin, A., Malm, J. & Eklund, A. (2021). Middle cerebral artery pressure laterality in patients with symptomatic ICA stenosis. PLOS ONE, 16(1), Article ID e0245337.
Open this publication in new window or tab >>Middle cerebral artery pressure laterality in patients with symptomatic ICA stenosis
Show others...
2021 (English)In: PLOS ONE, E-ISSN 1932-6203, Vol. 16, no 1, article id e0245337Article in journal (Refereed) Published
Abstract [en]

An internal carotid artery (ICA) stenosis can potentially decrease the perfusion pressure to the brain. In this study, computational fluid dynamics (CFD) was used to study if there was a hemispheric pressure laterality between the contra- and ipsilateral middle cerebral artery (MCA) in patients with a symptomatic ICA stenosis. We further investigated if this MCA pressure laterality (ΔPMCA) was related to the hemispheric flow laterality (ΔQ) in the anterior circulation, i.e., ICA, proximal MCA and the proximal anterior cerebral artery (ACA). Twenty-eight patients (73±6 years, range 59–80 years, 21 men) with symptomatic ICA stenosis were included. Flow rates were measured using 4D flow MRI data (PC-VIPR) and vessel geometries were obtained from computed tomography angiography. The ΔPMCA was calculated from CFD, where patient-specific flow rates were applied at all input- and output boundaries. The ΔPMCA between the contra- and ipsilateral side was 6.4±8.3 mmHg (p<0.001) (median 3.9 mmHg, range -1.3 to 31.9 mmHg). There was a linear correlation between the ΔPMCA and ΔQICA (r = 0.85, p<0.001) and ΔQACA (r = 0.71, p<0.001), respectively. The correlation to ΔQMCA was weaker (r = 0.47, p = 0.011). In conclusion, the MCA pressure laterality obtained with CFD, is a promising physiological biomarker that can grade the hemodynamic disturbance in patients with a symptomatic ICA stenosis.

Place, publisher, year, edition, pages
Public Library of Science, 2021
National Category
Medical Image Processing Neurology
Identifiers
urn:nbn:se:umu:diva-182247 (URN)10.1371/journal.pone.0245337 (DOI)000630020100027 ()33417614 (PubMedID)2-s2.0-85099353130 (Scopus ID)
Funder
Swedish Research Council, 2015–05616Swedish Research Council, 2017-04949Swedish Research Council, 2016-07213Swedish Heart Lung Foundation, 20140592
Available from: 2021-04-14 Created: 2021-04-14 Last updated: 2023-09-05Bibliographically approved
Holmgren, M., Wåhlin, A., Dunås, T., Malm, J. & Eklund, A. (2020). Assessment of Cerebral Blood Flow Pulsatility and Cerebral Arterial Compliance With 4D Flow MRI. Journal of Magnetic Resonance Imaging, 51(5), 1516-1525
Open this publication in new window or tab >>Assessment of Cerebral Blood Flow Pulsatility and Cerebral Arterial Compliance With 4D Flow MRI
Show others...
2020 (English)In: Journal of Magnetic Resonance Imaging, ISSN 1053-1807, E-ISSN 1522-2586, Vol. 51, no 5, p. 1516-1525Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Four-dimensional flow magnetic resonance imaging (4D flow MRI) enables efficient investigation of cerebral blood flow pulsatility in the cerebral arteries. This is important for exploring hemodynamic mechanisms behind vascular diseases associated with arterial pulsations.

PURPOSE: To investigate the feasibility of pulsatility assessments with 4D flow MRI, its agreement with reference two-dimensional phase-contrast MRI (2D PC-MRI) measurements, and to demonstrate how 4D flow MRI can be used to assess cerebral arterial compliance and cerebrovascular resistance in major cerebral arteries.

STUDY TYPE: Prospective.

SUBJECTS: Thirty-five subjects (20 women, 79 ± 5 years, range 70-91 years).

FIELD STRENGTH/SEQUENCE: 4D flow MRI (PC-VIPR) and 2D PC-MRI acquired with a 3T scanner.

ASSESSMENT: Time-resolved flow was assessed in nine cerebral arteries. From the pulsatile flow waveform in each artery, amplitude (ΔQ), volume load (ΔV), and pulsatility index (PI) were calculated. To reduce high-frequency noise in the 4D flow MRI data, the flow waveforms were low-pass filtered. From the total cerebral blood flow, total PI (PItot ), total volume load (ΔVtot ), cerebral arterial compliance (C), and cerebrovascular resistance (R) were calculated.

STATISTICAL TESTS: Two-tailed paired t-test, intraclass correlation (ICC).

RESULTS: There was no difference in ΔQ between 4D flow MRI and the reference (0.00 ± 0.022 ml/s, mean ± SEM, P = 0.97, ICC = 0.95, n = 310) with a cutoff frequency of 1.9 Hz and 15 cut plane long arterial segments. For ΔV, the difference was -0.006 ± 0.003 ml (mean ± SEM, P = 0.07, ICC = 0.93, n = 310) without filtering. Total R was 11.4 ± 2.41 mmHg/(ml/s) (mean ± SD) and C was 0.021 ± 0.009 ml/mmHg (mean ± SD). ΔVtot was 1.21 ± 0.29 ml (mean ± SD) with an ICC of 0.82 compared with the reference. PItot was 1.08 ± 0.21 (mean ± SD).

DATA CONCLUSION: We successfully assessed 4D flow MRI cerebral arterial pulsatility, cerebral arterial compliance, and cerebrovascular resistance. Averaging of multiple cut planes and low-pass filtering was necessary to assess accurate peak-to-peak features in the flow rate waveforms.

LEVEL OF EVIDENCE: 2

Technical Efficacy Stage: 2

Place, publisher, year, edition, pages
Wiley-Blackwell, 2020
Keywords
2D PC-MRI, 4D flow MRI, cerebral arterial compliance, cerebrovascular resistance, circle of Willis, pulsatility index
National Category
Medical Engineering
Identifiers
urn:nbn:se:umu:diva-165203 (URN)10.1002/jmri.26978 (DOI)000495792500001 ()31713964 (PubMedID)2-s2.0-85075025588 (Scopus ID)
Funder
Swedish Research Council, 2015–05616Swedish Heart Lung Foundation, 20140592Swedish Research Council, 2017-04949
Available from: 2019-11-20 Created: 2019-11-20 Last updated: 2023-03-24Bibliographically approved
Vikner, T., Nyberg, L., Holmgren, M., Malm, J., Eklund, A. & Wåhlin, A. (2020). Characterizing pulsatility in distal cerebral arteries using 4D flow MRI. Journal of Cerebral Blood Flow and Metabolism, 40(12), 2429-2440
Open this publication in new window or tab >>Characterizing pulsatility in distal cerebral arteries using 4D flow MRI
Show others...
2020 (English)In: Journal of Cerebral Blood Flow and Metabolism, ISSN 0271-678X, E-ISSN 1559-7016, Vol. 40, no 12, p. 2429-2440Article in journal (Refereed) Published
Abstract [en]

Recent reports have suggested that age-related arterial stiffening and excessive cerebral arterial pulsatility cause blood-brain barrier breakdown, brain atrophy and cognitive decline. This has spurred interest in developing non-invasive methods to measure pulsatility in distal vessels, closer to the cerebral microcirculation. Here, we report a method based on four-dimensional (4D) flow MRI to estimate a global composite flow waveform of distal cerebral arteries. The method is based on finding and sampling arterial waveforms from thousands of cross sections in numerous small vessels of the brain, originating from cerebral cortical arteries. We demonstrate agreement with internal and external reference methods and show the ability to capture significant increases in distal cerebral arterial pulsatility as a function of age. The proposed approach can be used to advance our understanding regarding excessive arterial pulsatility as a potential trigger of cognitive decline and dementia.

Place, publisher, year, edition, pages
Sage Publications, 2020
Keywords
4D flow MRI, cerebral hemodynamics, arterial pulsatility, cerebral cortical arteries, aging
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:umu:diva-166582 (URN)10.1177/0271678X19886667 (DOI)000497309400001 ()31722598 (PubMedID)2-s2.0-85075164443 (Scopus ID)
Funder
Swedish Research Council, 2015-05616Swedish Research Council, 2017-04949
Available from: 2019-12-20 Created: 2019-12-20 Last updated: 2023-03-24Bibliographically approved
Dunås, T., Holmgren, M., Wåhlin, A., Malm, J. & Eklund, A. (2019). Accuracy of blood flow assessment in cerebral arteries with 4D flow MRI: Evaluation with three segmentation methods. Journal of Magnetic Resonance Imaging, 50(2), 511-518
Open this publication in new window or tab >>Accuracy of blood flow assessment in cerebral arteries with 4D flow MRI: Evaluation with three segmentation methods
Show others...
2019 (English)In: Journal of Magnetic Resonance Imaging, ISSN 1053-1807, E-ISSN 1522-2586, Vol. 50, no 2, p. 511-518Article in journal (Refereed) Published
Abstract [en]

Background: Accelerated 4D flow MRI allows for high‐resolution velocity measurements with whole‐brain coverage. Such scans are increasingly used to calculate flow rates of individual arteries in the vascular tree, but detailed information about the accuracy and precision in relation to different postprocessing options is lacking.

Purpose: To evaluate and optimize three proposed segmentation methods and determine the accuracy of in vivo 4D flow MRI blood flow rate assessments in major cerebral arteries, with high‐resolution 2D PCMRI as a reference.

Study Type: Prospective.

Subjects: Thirty‐five subjects (20 women, 79 ± 5 years, range 70–91 years).

Field Strength/Sequence: 4D flow MRI with PC‐VIPR and 2D PCMRI acquired with a 3 T scanner.

Assessment: We compared blood flow rates measured with 4D flow MRI, to the reference, in nine main cerebral arteries. Lumen segmentation in the 4D flow MRI was performed with k‐means clustering using four different input datasets, and with two types of thresholding methods. The threshold was defined as a percentage of the maximum intensity value in the complex difference image. Local and global thresholding approaches were used, with evaluated thresholds from 6–26%.

Statistical Tests: Paired t‐test, F‐test, linear correlation (P < 0.05 was considered significant) along with intraclass correlation (ICC).

Results: With the thresholding methods, the lowest average flow difference was obtained for 20% local (0.02 ± 15.0 ml/min, ICC = 0.97, n = 310) or 10% global (0.08 ± 17.3 ml/min, ICC = 0.97, n = 310) thresholding with a significant lower standard deviation for local (F‐test, P = 0.01). For all clustering methods, we found a large systematic underestimation of flow compared with 2D PCMRI (16.1–22.3 ml/min).

Data Conclusion: A locally adapted threshold value gives a more stable result compared with a globally fixed threshold. 4D flow with the proposed segmentation method has the potential to become a useful reliable clinical tool for assessment of blood flow in the major cerebral arteries.

Level of Evidence: 2

Technical Efficacy: Stage 2

Keywords
magnetic resonance imaging, cerebral arteries, phase‐contrast MRI, 4D flow MRI, cerebral blood flow, Circle of Willis
National Category
Medical Image Processing
Identifiers
urn:nbn:se:umu:diva-147255 (URN)10.1002/jmri.26641 (DOI)000475681600017 ()30637846 (PubMedID)2-s2.0-85059966858 (Scopus ID)
Funder
Swedish Research Council, 2015–05616; 2017-04949Swedish Heart Lung Foundation, 20140592
Note

Originally included in thesis in manuscript form with title "Blood flow assessment in cerebral arteries with 4D flow MRI, concordance with 2D PCMRI"

Available from: 2018-04-30 Created: 2018-04-30 Last updated: 2023-03-24Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-1315-7010

Search in DiVA

Show all publications