Time‐resolved three‐dimensional phase‐contrast MRI

Abstract

Purpose:To demonstrate the feasibility of a four-dimensional phase contrast (PC) technique that permits spatial and temporal coverage of an entire three-dimensional volume, to quantitatively validate its accuracy against an established time resolved two-dimensional PC technique to explore advantages of the approach with regard to the fourdimensional nature of the data. Materials and Methods:Time-resolved, three-dimensional anatomical images were generated simultaneously with registered three-directional velocity vector fields. Improvements compared to prior methods include retrospectively gated and respiratory compensated image acquisition, interleaved flow encoding with freely selectable velocity encoding (venc) along each spatial direction, and flexible trade-off between temporal resolution and total acquisition time. Results:The implementation was validated against established two-dimensional PC techniques using a well-defined phantom, and successfully applied in volunteer and patient examinations. Human studies were performed after contrast administration in order to compensate for loss of inflow enhancement in the four-dimensional approach. Conclusion:Advantages of the four-dimensional approach include the complete spatial and temporal coverage of the cardiovascular region of interest and the ability to obtain high spatial resolution in all three dimensions with higher signal-to-noise ratio compared to two-dimensional methods at the same resolution. In addition, the four-dimensional nature of the data offers a variety of image processing options, such as magnitude and velocity multi-planar reformation, three-directional vector field plots, and velocity profiles mapped onto selected planes of interest.

Flow‐sensitive four‐dimensional cine magnetic resonance imaging for offline blood flow quantification in multiple vessels: A validation study

“…In our study, the bias and range of scatter were at nearly identical levels when comparing nongated 4D VEC MRI with gated 4D or 2D techniques. In quantitative flow acquisition, respiratory gating is usually applied for reducing bias that is introduced by respiratory motion (5,23). Alternatively, two or more signal averages can be obtained during free-breathing 2D flow acquisitions.…”

“…Flow-sensitive four-dimensional (4D) VEC MRI allows for acquisition of three-directional blood flow velocity information within a 3D anatomical volume (5). This technique was initially introduced to visualize blood flow patterns qualitatively in normal and pathological hemodynamic conditions (6)(7)(8).…”

Volumetric velocity measurements in restricted geometries using spiral sampling: a phantom study

“…Hence, in several 2D throughplane PC studies of maximum velocity and flow determinations in stenotic vessels, a multi-slice procedure was used [11,20]. With the advent of three-dimensional, three-directional velocity encoding sequences (here denoted 4D PC) [21][22][23], the possibility has emerged to quantify velocity and flow in multiple 4 dimensions, and in addition to visualize blood flow by streamlines and pathlines. These powerful possibilities offered by 4D PC have found a number of applications, and 4D PC has started to go beyond a visualization tool into a quantitative technique for extraction of velocity, flow and hemodynamically derived parameters such as wall shear stress [24] and kinetic energy [25].…”

Quantification in cardiac MRI: advances in image acquisition and processing

“…Such sequences have been coined 7D flow encoding and have the advantage of providing complete spatial and temporal resolution of velocity with a higher signal-to-noise ratio than 2D methods [38, 39]. Such acquisitions may be used for visualization of flow patterns in the heart and great arteries or for more accurate quantification of blood flow.…”