title: 3D phase contrast MRI: Partial volume correction for robust blood flow quantification in small intracranial vessels.
abstract: OBJECTIVE
  Recent advances in 3D-PCMRI (phase contrast MRI) sequences allow for measuring the complex hemodynamics in cerebral arteries. However, the small size of these vessels vs spatial resolution can lead to non-negligible partial volume artifacts, which must be taken into account when computing blood flow rates. For this purpose, we combined the velocity information provided by 3D-PCMRI with vessel geometry measured with 3DTOF (time of flight MRI) or 3DRA (3D rotational angiography) to correct the partial volume effects in flow rate assessments.
  
  
  METHODS
  The proposed methodology was first tested in vitro on cylindrical and patient specific vessels subject to fully controlled pulsatile flows. Both 2D- and 3D-PCMRI measurements using various spatial resolutions ranging from 20 to 1.3 voxels per vessel diameter were analyzed and compared with flowmeter baseline. Second, 3DTOF, 2D- and 3D-PCMRI measurements were performed in vivo on 35 patients harboring internal carotid artery (ICA) aneurysms indicated for endovascular treatments requiring 3DRA imaging.
  
  
  RESULTS
  The in vitro 2D- and 3D-PCMRI mean flow rates assessed with partial volume correction showed very low sensitivity to the acquisition resolution above ≈2 voxels per vessel diameter while uncorrected flow rates deviated critically when decreasing the spatial resolution. 3D-PCMRI flow rates measured in vivo in ICA agreed very well with 2D-PCMRI data and a good flow conservation was observed at the C7 bifurcation. Globally, partial volume correction led to 10-15% lower flow rates than uncorrected values as those reported in most of the published studies on intracranial flows.
  
  
  CONCLUSIONS
  Partial volume correction may improve the accuracy of PCMRI flow rate measurements especially in small vessels such as intracranial arteries. Magn Reson Med 79:129-140, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
authors.affiliation: Division of Neuroradiology, Geneva University Hospitals & Faculty of Medicine, University of Geneva, Geneva, Switzerland.|Laboratory for Hydraulic Machines (LMH), École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
authors.forename: Pierre
authors.initials: P
authors.lastname: Bouillot
authors.affiliation: Division of Radiology, Geneva University Hospitals, University of Geneva, Geneva, Switzerland.
authors.forename: Bénédicte M A
authors.initials: BMA
authors.lastname: Delattre
authors.affiliation: Division of Neuroradiology, Geneva University Hospitals & Faculty of Medicine, University of Geneva, Geneva, Switzerland.|Division of Neuroradiology, Department of Medical Imaging, Toronto Western Hospital, University Health Network, Toronto, Canada.
authors.forename: Olivier
authors.initials: O
authors.lastname: Brina
authors.affiliation: Division of Neuroradiology, Geneva University Hospitals & Faculty of Medicine, University of Geneva, Geneva, Switzerland.
authors.forename: Rafik
authors.initials: R
authors.lastname: Ouared
authors.affiliation: Laboratory for Hydraulic Machines (LMH), École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Farhat
authors.affiliation: Biomedical Simulation Laboratory, Department of Mechanical & Industrial Engineering, University of Toronto, Toronto, Canada.
authors.forename: Christophe
authors.initials: C
authors.lastname: Chnafa
authors.affiliation: Biomedical Simulation Laboratory, Department of Mechanical & Industrial Engineering, University of Toronto, Toronto, Canada.
authors.forename: David A
authors.initials: DA
authors.lastname: Steinman
authors.affiliation: Division of Neuroradiology, Geneva University Hospitals & Faculty of Medicine, University of Geneva, Geneva, Switzerland.
authors.forename: Karl-Olof
authors.initials: KO
authors.lastname: Lovblad
authors.affiliation: Division of Neuroradiology, Geneva University Hospitals & Faculty of Medicine, University of Geneva, Geneva, Switzerland.|Division of Neuroradiology, Department of Medical Imaging, Toronto Western Hospital, University Health Network, Toronto, Canada.|Division of Neurosurgery, Department of Surgery, Toronto Western Hospital, University Health Network, Toronto, Canada.
authors.forename: Vitor M
authors.initials: VM
authors.lastname: Pereira
authors.affiliation: Division of Neuroradiology, Geneva University Hospitals & Faculty of Medicine, University of Geneva, Geneva, Switzerland.
authors.forename: Maria I
authors.initials: MI
authors.lastname: Vargas
mesh_terms: D000328:Adult; D016477:Artifacts; D001783:Blood Flow Velocity; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging*; D002536:Cerebral Arteries / Q000000981:diagnostic imaging; D002560:Cerebrovascular Circulation; D005260:Female; D006439:Hemodynamics; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D002532:Intracranial Aneurysm / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D011673:Pulsatile Flow
keywords: PCMRI; Partial volume correction; blood flow; intracranial arteries