Pulsatile blood flow through the cavities of the heart and great vessels is time-varying and multidirectional. Access to all regions, phases and directions of cardiovascular flows has formerly been limited. Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) has enabled more comprehensive access to such flows, with typical spatial resolution of 1.5×1.5×1.5 – 3×3×3 mm3, typical temporal resolution of 30–40 ms, and acquisition times in the order of 5 to 25 min. This consensus paper is the work of physicists, physicians and biomedical engineers, active in the development and implementation of 4D Flow CMR, who have repeatedly met to share experience and ideas. The paper aims to assist understanding of acquisition and analysis methods, and their potential clinical applications with a focus on the heart and greater vessels. We describe that 4D Flow CMR can be clinically advantageous because placement of a single acquisition volume is straightforward and enables flow through any plane across it to be calculated retrospectively and with good accuracy. We also specify research and development goals that have yet to be satisfactorily achieved. Derived flow parameters, generally needing further development or validation for clinical use, include measurements of wall shear stress, pressure difference, turbulent kinetic energy, and intracardiac flow components. The dependence of measurement accuracy on acquisition parameters is considered, as are the uses of different visualization strategies for appropriate representation of time-varying multidirectional flow fields. Finally, we offer suggestions for more consistent, user-friendly implementation of 4D Flow CMR acquisition and data handling with a view to multicenter studies and more widespread adoption of the approach in routine clinical investigations.

Cardiac MRI plays an important role in the evaluation of cardiovascular diseases (CVDs), including ischemic heart disease, cardiomyopathy, valvular disease, congenital disease, pericardial disease, and masses. Large multicenter trials have shown the positive impact of MRI-based management on outcomes in several CVDs. These results have made MRI an indispensable technique in the evaluation of these diseases, and cardiac MRI has an important role in multisociety guidelines. MRI is the reference standard for quantification of ventricular volumes and function. Flow imaging enables accurate quantification of flow and velocities through valves, shunts, and surgical conduits or baffles. Late gadolinium enhancement and parametric mapping techniques enable tissue characterization and yield prognostic information. In the past decade, cardiac MRI technology has seen rapid advances in both hardware and sequences. Multiple novel sequences, such as parametric mapping and four-dimensional flow, are increasingly being incorporated into routine clinical practice. Acceleration strategies have matured, allowing faster acquisition of cardiac MRI sequences in patients with arrhythmia and poor breath holding. Challenges of cardiac MRI at high-field-strength magnets and in patients with indwelling cardiac devices or severe renal dysfunction have been mitigated. Artificial intelligence techniques are decreasing the complexity of MRI acquisition and postprocessing. This article reviews the current state of the art and emerging techniques in cardiac MRI.

With recent improvement in hardware and software techniques, magnetic resonance angiography (MRA) has undergone significant changes in technique and approach. The advent of 3.0 T magnets has allowed reduction in exogenous contrast dose without compromising overall image quality. The use of novel intravascular contrast agents substantially increases the image windows and decreases contrast dose. Additionally, the lower risk and cost in non-contrast enhanced (NCE) MRA has sparked renewed interest in these methods. This article discusses the current state of both contrast-enhanced (CE) and NCE-MRA. New CE-MRA methods take advantage of dose reduction at 3.0 T, novel contrast agents, and parallel imaging methods. The risks of gadolinium-based contrast media, and the NCE-MRA methods of time-of-flight, steady-state free precession, and phase contrast are discussed.

Purpose To compare pulmonary artery flow using Cartesian and radially sampled four‐dimensional flow‐sensitive (4D flow) MRI at two institutions. Methods Nineteen healthy subjects and 17 pulmonary arterial hypertension (PAH) subjects underwent a Cartesian 4D flow acquisition (institution 1) or a three‐dimensional radial acquisition (institution 2). The diameter, peak systolic velocity (Vmax), peak flow (Qmax), stroke volume (SV), and wall shear stress (WSS) were computed in two‐dimensional analysis planes at the main, right, and left pulmonary artery. Interobserver variability, interinstitutional differences, flow continuity, and the hemodynamic measurements in healthy and PAH subjects were assessed. Results Vmax, Qmax, SV, and WSS at all locations were significantly lower (P < 0.05) in PAH compared with healthy subjects. The limits of agreement were 0.16 m/s, 2.4 L/min, 10 mL, and 0.31 N/m² for Vmax, Qmax, SV, and WSS, respectively. Differences between Qmax and SV using Cartesian and radial sequences were not significant. Plane placement and acquisition exhibited isolated, site‐based differences between Vmax and WSS. Conclusions 4D flow MRI was used to detect differences in pulmonary artery hemodynamics for PAH subjects. Flow and WSS in healthy and PAH subject cohorts were similar between Cartesian‐ and radial‐based 4D flow MRI acquisitions with minimal interobserver variability. Magn Reson Med 73:1904–1913, 2015.