Keywords:
Dilatation, Imaging sequences, Computer Applications-3D, MR-Angiography, MR, Cardiovascular system, Arteries / Aorta, Aneurysms
Authors:
M. Sugiyama1, Y. Takehara1, T. Saito1, N. Ooishi1, M. Alley2, T. Wakayama3, M. Terada4, S. Yoshihara4, H. Sakahara1; 1Hamamatsu/JP, 2Stanford, CA/US, 3Hino/JP, 4Iwata/JP
DOI:
10.1594/ecr2013/C-2504
Methods and Materials
Three AS patients diagnosed with echocardiography and cardiac catheterization were examined on 3T MR scanner.
ECG gated,
gradient-echo-based coronal 4D-Flow covering the whole heart and the ascending aorta was performed following the contrast enhanced MR Angiography (Gd3DMRA) performed for the determination of the aortic boundary.
Age-matched five patients without AS were also examined in a same way.
Written informed consent was acquired in all patients.
MR imaging
All examinations were performed on 3.0T MR scanner (Discovery 750,
GE Healthcare,
WI,
USA).
2D PC cine study
Prior to 4D-Flow,
2D PC cine was performed on the transverse section.
The maximum flow velocity was calculated within the thoracic aorta,
and the velocity encoding value (VENC) was determined.
Gd 3D MRA
Prior to flow measurements,
time resolved contrast enhanced 3 dimensional MR angiography (Gd3DMRA) was performed with a bolus injection of gadolinium chelate (0.1 mmol/kg).
A 3D data set of arterial dominant phase was picked out and was used to determine the boundary of the inner wall of the arteries.
Then,
4D-Flow was performed 4D-Flow data acquisitions: The 4D-Flow is based on a SPGR sequence encoding flow velocities in three orthogonal directions.
The parameters used were TR/TE/FA/NEX of 4.5-5.5/2.0-3.0/15/1,
FOV of 32 cm,
Matrix of 224x224,
2 mm thickness,
60 partitions,
12-20 phases during one cardiac cycle and imaging time of 10 min (with reduction factor of 2).
ECG gating and respiratory compensation were also combined.
VENC was optimized based on the values measured with 2D PC cine study performed prior to the 4Dflow.
Acquired data were transferred to a workstation and were post-processed with flow analysis software (flova,
R-`tech,
Japan).
The velocity data derived from 4D-Flow and the geometric data of the boundary of the aortic wall determined by Gd3DMRA were interpolated,
and we could delineate streamlines or calculate the wall shear stress (WSS) of the arbitrary arteries within the field of view,
and can overview the change of WSS related to cardiac cycle as color maps.