4D flow MRI

Abstract

Traditionally, magnetic resonance imaging (MRI) of flow using phase contrast (PC) methods is accomplished using methods that resolve single‐directional flow in two spatial dimensions (2D) of an individual slice. More recently, three‐dimensional (3D) spatial encoding combined with three‐directional velocity‐encoded phase contrast MRI (here termed 4D flow MRI) has drawn increased attention. 4D flow MRI offers the ability to measure and to visualize the temporal evolution of complex blood flow patterns within an acquired 3D volume. Various methodological improvements permit the acquisition of 4D flow MRI data encompassing individual vascular structures and entire vascular territories such as the heart, the adjacent aorta, the carotid arteries, abdominal, or peripheral vessels within reasonable scan times. To subsequently analyze the flow data by quantitative means and visualization of complex, three‐directional blood flow patterns, various tools have been proposed. This review intends to introduce currently used 4D flow MRI methods, including Cartesian and radial data acquisition, approaches for accelerated data acquisition, cardiac gating, and respiration control. Based on these developments, an overview is provided over the potential this new imaging technique has in different parts of the body from the head to the peripheral arteries. J. Magn. Reson. Imaging 2012;. © 2012 Wiley Periodicals, Inc.

Test–retest multisite reproducibility of neurovascular 4D flow MRI

“…The 4D flow MRI has been widely used in cardiovascular systems to assess dynamic characteristics of blood flow. 17 It offers a variety of parameters that may assist characterization of the blood hemodynamics. Although the validity of the 4D flow technique has been demonstrated through comparison with established techniques such as 2D PC MRI and ultrasound, as well as in experimental setup, the reproducibility and reliability of this technique still need investigation with large cohorts to support its widespread clinical use.…”

“…In recent years, with the development of fast imaging strategies, the 3D time-resolved phase-contrast MRI with velocity-encoding along three axes (termed 4D flow MRI) technique has become clinically feasible. 17,18 In addition to assessment of the flow velocity, the 4D flow MRI technique allows for the evaluation of several additional hemodynamic parameters that may be derived from the velocity information, such as wall shear stress (WSS), 6,19 blood pressure difference, 20 turbulence kinetic energy, 21 and viscous energy loss, 22 etc. Previous studies have demonstrated clinical applications of this technique for improved characterization of hemodynamics in neurovascular systems, 1,23,24 intraheart and great vessels, 25 and peripheral vessels.…”

Improved quantification and mapping of anomalous pulmonary venous flow with four‐dimensional phase‐contrast MRI and interactive streamline rendering

“…Currently, the most common approaches for streamline and pathline visualization for 4D-PC data rely on some form of vessel segmentation for streamline visualization. 26 Such segmentations can be timeconsuming to perform, especially for smaller vessels. Rather than rely on anatomic segmentation to enable streamline rendering, we propose the reverse in this work-that interactive streamline rendering can instead guide delineation and connectivity of small pulmonary veins.…”

Relative pressure estimation from velocity measurements in blood flows: State‐of‐the‐art and new approaches

“…While RPD is most often evaluated clinically using doppler echocardiography, 3D-PCMRI is gaining increasing popularity since it permits quantification of complex blood flow patterns in large vessels and the heart. 7 Moreover, recent work has demonstrated that incorporating the spatial variation not typically observed in standard echo images can have a significant impact on the pressure estimates. 8 3D-PCMRI allows measurement of the velocity field with spatial and temporal resolutions typically ranging from 1.5 to 3 mm 3 and 20 to 40 ms, respectively, and noise levels of around 15% of the maximal velocity.…”