Accelerated dual-venc 4D flow MRI for neurovascular applications.
To improve velocity-to-noise ratio (VNR) and dynamic velocity range of 4D flow magnetic resonance imaging (MRI) by using dual-velocity encoding (dual-venc) with k-t generalized autocalibrating partially parallel acquisition (GRAPPA) acceleration.



A dual-venc 4D flow MRI sequence with k-t GRAPPA acceleration was developed using a shared reference scan followed by three-directional low- and high-venc scans (repetition time / echo time / flip angle = 6.1 msec / 3.4 msec / 15°, temporal/spatial resolution = 43.0 msec/1.2 × 1.2 × 1.2 mm3). The high-venc data were used to correct for aliasing in the low-venc data, resulting in a single dataset with the favorable VNR of the low-venc but without velocity aliasing. The sequence was validated with a 3T MRI scanner in phantom experiments and applied in 16 volunteers to investigate its feasibility for assessing intracranial hemodynamics (net flow and peak velocity) at the major intracranial vessels. In addition, image quality and image noise were assessed in the in vivo acquisitions.



All 4D flow MRI scans were acquired successfully with an acquisition time of 20 ± 4 minutes. The shared reference scan reduced the total acquisition time by 12.5% compared to two separate scans. Phantom experiments showed 51.4% reduced noise for dual-venc compared to high-venc and an excellent agreement of velocities (ρ = 0.8, P < 0.001). The volunteer data showed decreased noise in dual-venc data (54.6% lower) compared to high-venc, and improved image quality, as graded by two observers: fewer artifacts (P < 0.0001), improved vessel conspicuity (P < 0.0001), and reduced noise (P < 0.0001).



Dual-venc 4D flow MRI exhibits the superior VNR of the low-venc acquisition and reliably incorporates low- and high-velocity fields simultaneously. In vitro and in vivo data demonstrate improved flow visualization, image quality, and image noise.



2 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:102-114.
Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
Susanne
S
Schnell
Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.|Department of Neurosurgery, Northwestern University, Chicago, Illinois, USA.
Sameer A
SA
Ansari
Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.|Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Chicago, Illinois, USA.
Can
C
Wu
Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.|Department of Cardiac Sciences - Stephenson Cardiac Imaging Centre, Cumming School of Medicine, University of Calgary, Calgary, Canada.
Julio
J
Garcia
Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
Ian G
IG
Murphy
Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
Ozair A
OA
Rahman
Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
Amir A
AA
Rahsepar
Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
Maria
M
Aristova
Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
Jeremy D
JD
Collins
Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
James C
JC
Carr
Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.|Department of Neurosurgery, Northwestern University, Chicago, Illinois, USA.
Michael
M
Markl
D000328:Adult; D001783:Blood Flow Velocity; D001921:Brain / Q000000981:diagnostic imaging / Q000502:physiology*; D055424:Cardiac-Gated Imaging Techniques / Q000379:methods; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000295:instrumentation / Q000379:methods*; D008297:Male; D064847:Multimodal Imaging / Q000379:methods; D059906:Neuroimaging / Q000295:instrumentation / Q000379:methods; D000069336:Neurovascular Coupling / Q000502:physiology*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted
4D flow MRI; PC-MRI; dual venc; intracranial 4D flow MRI; k-t GRAPPA