Can Wu

Cynthia K Rigsby

Joshua D Robinson

Julio Garcia

Michael J Rose

Michael Markl

Susanne Schnell

Journal of Cardiovascular Magnetic Resonance

Springer - Publisher Connector

Improved assessment of aortic hemodynamics by k-t accelerated dual-venc 4D flow MRI in pediatric patients

ORAL PRESENTATION Open Access
Improved assessment of aortic hemodynamics by
k-t accelerated dual-venc 4D flow MRI in pediatric
patients
Susanne Schnell1*, Michael J Rose2,1, Can Wu1,3, Julio Garcia1, Joshua D Robinson4, Michael Markl1,3,
Cynthia K Rigsby2
From 19th Annual SCMR Scientific Sessions
Los Angeles, CA, USA. 27-30 January 2016
Background
Bicuspid aortic valve (BAV) is often associated with aor-
tic stenosis, resulting in high velocity blood flow in the
ascending aorta, with slow flow areas in the dilated
aorta or adjacent vessels. Similarly, Marfan syndrome
patients develop aortic root dilatation and regurgitation
with both high and low velocity blood flow. 4D flow
MRI is typically acquired with a velocity encoding (venc)
gradient adjusted to the estimated peak velocity. As the
velocity noise is directly related to the velocity sensitivity
(sv~venc), a high venc can substantially limit the assess-
ment of low flow velocities (v < < venc). We therefore
developed a fully integrated low- and high-venc PC-MRI
in a single measurement (dual-venc) to avoid aliasing
and improve velocity-to-noise ratio (VNR).
Methods
In addition to standard clinical contrast enhanced cardiac
MRI, k-t GRAPPA accelerated dual-venc 4D flow MRI was
acquired with full volumetric coverage of the ascending
(AAo) and descending (DAo) aorta in 4 Marfan syndrome
patients (age = 16.3 ± 1.9 yrs, 1 female, low-venc = 81 cm/
s, high-venc = 200 cm/s) and 1 BAV patient (age = 20 yrs,
male, low-venc = 125 cm/s, high-venc = 350 cm/s) on a
1.5T Siemens MAGNETOM Aera MRI scanner with the
following imaging parameters: R = 5, TE/TR = 2.93 ±
0.08/5.46 ± 0.08ms, voxel size = 1.9 × 1.9 × 2.0 mm3.
Background correction was performed separately of the
low- and high-venc phase images. High-venc data were
used for complete anti-aliasing of the low-venc data while
maintaining the favorable VNR of the low-venc data.
A pseudo-complex MRA was derived from the 4D flow
data and used to segment the angiogram using commer-
cial software (MIMICS, Materialize). Velocity noise was
estimated in static tissue using region of interest analysis.
Velocity maximum intensity projection maps (MIPs) were
calculated and used to determine peak velocities in the
overall aorta and in the three sub-segments AAo, Arch
and DAo. In addition, blood flow was visualized using
streamlines within the segmented vessels during peak
systole.
Results
Velocity noise was significantly improved in the dual-
venc 4D flow data by 230% ± 20% compared to the
high-venc velocity scan for the four Marfan patients,
which corresponded with the high-venc/low-venc ratio
of 2.5. In the BAV patient, velocity noise was improved
by 276% in the dual-venc compared to the high-venc
scan (high-venc/low-venc ratio=2.4). Peak velocity showed
significant correlation between high- and dual-venc results
in the AAo (R2 = 0.85, p = 0.04) and Arch (R2 = 0.95, p =
0.006) using velocity MIP analysis. Streamline comparison
showed substantially improved qualitative visualization of
aortic blood flow patterns and more coherent streamlines
especially in slow flow areas and no aliasing artifacts in
areas that were aliased in the low-venc images.
Conclusions
This feasibility study demonstrates the potential of k-t
accelerated dual-venc 4D flow MRI to improve the assess-
ment of aortic hemodynamics with large dynamic range
while maintaining the scan time of standard 4D flow MRI.
1Dept. of Radiology, Northwestern University, Feinberg Medical School,
Chicago, IL, USA
Full list of author information is available at the end of the article
Schnell et al. Journal of Cardiovascular Magnetic
Resonance 2016, 18(Suppl 1):O96
http://www.jcmr-online.com/content/18/S1/O96
© 2016 Schnell et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://
creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the
original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/
zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Authors’ details
1Dept. of Radiology, Northwestern University, Feinberg Medical School,
Chicago, IL, USA. 2Pediatric Radiology, Lurie Children’s Hospital of Chicago,
Chicago, IL, USA. 3McCormick School of Engineering, Northwestern
University, Evanston, IL, USA. 4Pediatrics-Cardiology, Lurie Children’s Hospital
of Chicago, Chicago, IL, USA.
Published: 27 January 2016
doi:10.1186/1532-429X-18-S1-O96
Cite this article as: Schnell et al.: Improved assessment of aortic
hemodynamics by k-t accelerated dual-venc 4D flow MRI in pediatric
patients. Journal of Cardiovascular Magnetic Resonance 2016 18(Suppl 1):
O96.
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Figure 1
Schnell et al. Journal of Cardiovascular Magnetic
Resonance 2016, 18(Suppl 1):O96
http://www.jcmr-online.com/content/18/S1/O96
Page 2 of 2


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Improved assessment of aortic hemodynamics by k-t accelerated dual-venc 4D flow MRI in pediatric patients

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