While comparable to 2D cardiac MR velocity mapping, comprehensive 3D velocity acquisition could be relatively operator independent, and potentially yield information on blood flow in patients with congenital or valvular heart disease, according to research published this month in the Journal of Cardiovascular Magnetic Resonance.
Two-dimensional, uni-directionally encoded, cardiovascular MR (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.
Researchers sought 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.
Using a 1.5T Phillips Intera CMR system, 3D acquisitions were done with an anisotropic 3D segmented k-space phase contrast gradient echo sequence with a short EPI readout, as well as prospective ECG and diaphragm navigator gating. The 2D acquisitions used segmented k-space phase contrast with prospective ECG and diaphragm navigator gating. The researchers performed quantitative flow analyses retrospectively with dedicated software for both the in vivo and in vitro acquisitions.
"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," the authors wrote.
Analysis of in vitro data found the 3D technique to have overestimated the continuous flow rate by approximately 5 percent across the entire applied flow range. The in vivo analysis found that the 2D and the 3D techniques yielded similar volumetric flow curves and measurements. Each in vivo 3D acquisition took about eight minutes or more.
The investigators concluded that flow measurements derived from the 3D and 2D acquisitions were comparable; however, although it was time consuming, comprehensive 3D velocity acquisition could be relatively operator independent and potentially yield information on flow through several retrospectively chosen planes, for example in patients with congenital or valvular heart disease.