11:00 |
63. |
Coregistration of
Wall Shear Stress and Plaque Distribution Within the
Thoracic Aorta of Acute Stroke Patients
Michael Markl1, Stephanie
Brendecke2, Jan Simon1, Alex
Frydrychowicz3, Andreas Harloff2
1Diagnostic
Radiology, Medical Physics, University Hospital, Freiburg,
Germany; 2Neurology, University Hospital,
Freiburg, Germany; 3Radiology, University of
Wisconsin, Madison, United States
Flow-sensitive 4D-MRI (3D morphology and 3-directional blood
flow) and segmental wall shear stress analysis were employed
in 94 patients with aortic atherosclerosis. A one-to-one
comparison of wall parameter distribution with plaque
location was performed in a large number of complex aortic
plaques. Critical wall parameters such as low wall shear
stress and high oscillatory shear index were concentrated at
the inner curvature of the aorta and near the outlet of the
supra-aortic arteries. For most complex plaques a consistent
location of critical wall parameters in wall segments
adjacent to the atheroma suggested a close correlation of
hemodynamics and advanced atherosclerosis. |
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11:12 |
64. |
Analysis of Right
Atrial and Ventricular Flow Patterns with Whole Heart 4D
Flow MRI – Comparison of Tetralogy of Fallot with Normal
Volunteers
Christopher J. François1,
Shardha Srinivasan2, Benjamin R. Landgraf1,
Alex Frydrychowicz1, Scott B. Reeder1,3,
Mark L. Schiebler1, Oliver Wieben1,3
1Radiology,
University of Wisconsin, Madison, WI, United States; 2Pediatrics,
University of Wisconsin, Madison, WI, United States; 3Medical
Physics, University of Wisconsin, Madison, WI, United States
An
appropriate understanding of cardiac function requires
analysis of flow patterns through the heart. This is
particularly true in congenital heart disease prior to and
following repair, where reconstruction of a normally
functioning heart would be desirable. This work describes
the analysis of flow patterns in the right heart in normal
volunteers and patients with Tetralogy of Fallot using whole
heart 4D flow MRI. |
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11:24 |
65. |
Simultaneous
Quantification of Blood Velocity and Oxygenation in Femoral
Artery and Vein in Response to Cuff-Induced Ischemia
Michael C. Langham1,
Jeremy Magland1, Felix W. Wehrli1
1Radiology,
University of Pennsylvania, Philadelphia, PA, United States
Quantifying reactive hyperemia in the lower extremities is a
common approach for assessing vascular dysfunction
associated with peripheral arterial disease (PAD). Often
assessment is limited to measuring a single physiologic
parameter such as velocity, flow-mediated dilatation and
blood oxygenation. As a first step toward the development of
an integrated MRI examination of PAD we have combined
velocity quantification technique with a field mapping pulse
sequence allowing simultaneous time-course mapping of blood
velocity and oxygenation in femoral artery and vein during
cuff-induced hyperemia. The results of blood velocity and
oxygenation quantification agree with those found in the
literature. |
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11:36 |
66. |
5-Point,
Ultra-Short TE, 3D Radial Phase Contrast: Improved
Characterization of Complex and
Turbulent Flow
Kevin M . Johnson1
1Medical Physics,
University of Wisconsin - Madison, Madison, WI, United
States
The
accuracy of PC MR is deteriorated by flow features common to
pathology such as acceleration, unstable flow, and
turbulence. Recently, ultra short TE 2D radial sequences
have been shown to provide more reliable through plane flow
measurements than standard PC. Meanwhile, investigators
have utilized conventional 3D PC sequences for the
measurement of turbulence kinetic energy using signal
losses. In this work, we investigate a synergistic
combination of ultra-short TE 3D radial trajectories and a
5-point velocity encoding scheme for improvements in both
the velocity measurement accuracy and estimation of
intra-voxel standard deviations utilized for turbulence
mapping. |
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11:48 |
67. |
Hadamard-Transform K-T PCA for Cine 3D Velocity Vector Field
Mapping of Carotid Flow
Verena Knobloch1,
Daniel Giese1, Peter Boesiger1,
Sebastian Kozerke1
1Institute for
Biomedical Engineering, Swiss Federal Institute of Technology
and University Zurich, Zurich, Switzerland
It
has been shown recently that k-t PCA permits high
acceleration without compromising the accuracy of single
directional flow quantification. In this work 3D velocity
fields are measured in a phantom and an in-vivo case and
reconstructed with different acceleration factors. Pathline
tracking is possible up to an acceleration factor of 10. |
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12:00 |
68. |
Metric Optimized
Gating for Fetal Cardiac MR Imaging
Michael Shelton Jansz1,2,
Mike Seed3, Joshua F. van Amerom1,2,
Shi Joon Yoo3,4, Christopher K. Macgowan1,2
1Medical Biophysics,
University of Toronto and Hospital for Sick Children,
Toronto, Ontario, Canada; 2Medical Imaging,
University of Toronto and Hospital for Sick Children,
Toronto, Ontario, Canada; 3Pediatric Cardiology,
University of Toronto and Hospital for Sick Children,
Toronto, Ontario, Canada; 4Dignostic Imaging,
University of Toronto and Hospital for Sick Children,
Toronto, Ontario, Canada
Phase-contrast MRI of pulsatile flow typically requires
cardiac gating; however, a gating signal is not necessarily
available in utero for fetal cardiac imaging. We
propose a new technique for reconstructing ungated data
where the gating is determined retrospectively by optimizing
an image metric. Simulations and in vivo data are
presented to demonstrate the feasibility of this technique. |
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12:12 |
69. |
Objective
Characterization of Disease Severity by Determination of
Blood Flow Reserve Capacity of the Popliteal Artery in
Intermittent Claudication
Bastiaan Versluis1,
Marjolein HG Dremmen1, Patty J. Nelemans2,
Joachim E. Wildberger1, Tim Leiner1,
Walter H. Backes1
1Radiology,
Maastricht Universitary Medical Centre, Maastricht,
Netherlands; 2Epidemiology, Maastricht
Universitary Medical Centre, Maastricht, Netherlands
Objective characterization of peripheral arterial disease
(PAD) severity remains difficult purely on the basis of
morphological assessement. We describe a method to determine
rest flow and blood flow reserve capacity (BFRC) of the
popliteal artery, using serial velocity encoded 2D MR cine
PCA flow measurements. Using this method, we found a strong
reduction in rest flow, maximum flow and BFRC in 10 patients
with intermittent claudication compared to 10 healthy
subjects. This method can potentially be used to supplement
MR angiography to objectively characterize PAD disease
severity and to monitor therapy efficacy in intermittent
claudication. |
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12:24 |
70. |
Analysis of
Complex Flow Patterns with Acceleration-Encoded MRI
Felix Staehle1,
Simon Bauer1, Bernd André Jung1,
Jürgen Hennig1, Michael Markl1
1Department of
Diagnostic Radiology, University Hospital Freiburg,
Freiburg, Germany
The
phase contrast principle (PC) can be employed to measure
flow acceleration by using acceleration sensitive encoding
gradients. The aim of this study was to evaluate a newly
developed gradient optimized acceleration-sensitive PC-MRI
technique with full three-directional acceleration encoding
of aortic blood flow. Results were compared to standard
velocity encoded phase contrast MRI. In addition, the value
of acceleration induced intravoxel dephasing as a new image
contrast providing information about complex and vortical
flow was investigated. |
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12:36 |
71. |
Novel Hybrid
Real-Time Phase-Contrast Sequence
Jennifer Anne Steeden1,2,
David Atkinson1, Andrew M. Taylor2,
Vivek Muthurangu2
1Medical Physics,
University College London, London, United
Kingdom; 2Centre for Cardiovascular MR, UCL
Institute of Child Health, London,
United Kingdom
Real-time phase contrast (PC) imaging has a low temporal
resolution because interleaved flow-encoded and compensated
readouts must be acquired. We have developed a hybrid
real-time PC sequence that acquires real-time flow-encoded
and flow-compensated readouts in alternating blocks. The
encoded data is subsequently matched to the compensated
data, allowing the temporal resolution to be effectively
doubled. This technique was demonstrated in 10 volunteers to
adequately match the flow-compensated data to the
flow-encoded data. It was also shown to accurately measure
stroke volumes, with a good correlation against a reference
gated sequence and an in-house real-time interleaved flow
sequence. |
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12:48 |
72. |
Analysis and
Correction of Background Velocity Offsets in Cine
Phase-Contrast Imaging Using Magnetic Field Monitoring
Daniel Giese1,2,
Maximilian Haeberlin1, Christoph Barmet1,
Tobias Schaeffter2, Klaas Paul Pruessmann1,
Sebastian Kozerke1,2
1Institute for
Biomedical Engineering, University and ETH Zurich, Zurich,
Switzerland; 2Division of Imaging Sciences,
King's College London, London, United Kingdom
The
sensitivity of phase contrast MRI to magnetic field gradient
imperfections has long been recognized and a number of
image-based approaches exist to partially correct for
background velocity offsets. Image-based velocity offset
correction assumes a sufficient number of static image
pixels and often only phase offsets with 0th and 1st order
in space can be accounted for. In this work, a 16-channel
magnetic field camera is employed to analyze and correct
background velocity offsets in cine phase-contrast velocity
imaging. It is demonstrated that phase offsets exhibit
primarily constant and linear terms in space but do
considerably vary in magnitude over time in triggered cine
sequences necessitating heart-phase dependent correction. |
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