Three dimensional three component whole heart cardiovascular magnetic resonance velocity mapping: comparison of flow measurements from 3D and 2D acquisitions.
BACKGROUND
Two-dimensional, unidirectionally encoded, cardiovascular magnetic resonance (CMR) velocity mapping is an established technique for the quantification of blood flow in large vessels. However, it requires an operator to correctly align the planes of acquisition. If all three directional components of velocity are measured for each voxel of a 3D volume through the phases of the cardiac cycle, blood flow through any chosen plane can potentially be calculated retrospectively. The initial acquisition is then more time consuming but relatively operator independent.


OBJECTIVE
To compare the curves and volumes of flow derived from conventional 2D and comprehensive 3D flow acquisitions in a steady state flow model, and in vivo through planes transecting the ascending aorta and pulmonary trunk in 10 healthy volunteers.


METHODS
Using a 1.5 T Phillips Intera CMR system, 3D acquisitions used an anisotropic 3D segmented k-space phase contrast gradient echo sequence with a short EPI readout, with prospective ECG and diaphragm navigator gating. The 2D acquisitions used segmented k-space phase contrast with prospective ECG and diaphragm navigator gating. Quantitative flow analyses were performed retrospectively with dedicated software for both the in vivo and in vitro acquisitions.


RESULTS
Analysis of in vitro data found the 3D technique to have overestimated the continuous flow rate by approximately 5% across the entire applied flow range. In vivo, the 2D and the 3D techniques yielded similar volumetric flow curves and measurements. Aortic flow: (mean +/- SD), 2D = 89.5 +/- 13.5 ml & 3D = 92.7 +/- 17.5 ml. Pulmonary flow: 2D = 98.8 +/- 18.4 ml & 3D = 94.9 +/- 19.0 ml). Each in vivo 3D acquisition took about 8 minutes or more.


CONCLUSIONS
Flow measurements derived from the 3D and 2D acquisitions were comparable. Although time consuming, comprehensive 3D velocity acquisition could be relatively operator independent, and could potentially yield information on flow through several retrospectively chosen planes, for example in patients with congenital or valvular heart disease.
Brix
Lau
L
Department of Biomedical Engineering, Region Midtjylland, c/o Aarhus University Hospital, Skejby, Denmark. lau.brix@stab.rm.dk
Ringgaard
Steffen
S
Rasmusson
Allan
A
Sørensen
Thomas Sangild
TS
Kim
W Yong
WY
D000328:Adult; D001783:Blood Flow Velocity; D003326:Coronary Circulation; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male