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

Abstract

Background Cardiac MRI is routinely performed for quantification of shunt flow in patients with anomalous pulmonary veins, but can be technically-challenging to perform. Four-dimensional phase-contrast (4D-PC) MRI has potential to simplify this exam. We sought to determine whether 4D-PC may be a viable clinical alternative to conventional 2D phase-contrast MR imaging. Methods With institutional review board approval and HIPAA-compliance, we retrospectively identified all patients with anomalous pulmonary veins who underwent cardiac MRI at either 1.5 Tesla (T) or 3T with parallel-imaging compressed-sensing (PI-CS) 4D-PC between April, 2011 and October, 2013. A total of 15 exams were included (10 male, 5 female). Algorithms for interactive streamline visualization were developed and integrated into in-house software. Blood flow was measured at the valves, pulmonary arteries and veins, cavae, and any associated shunts. Pulmonary veins were mapped to their receiving atrial chamber with streamlines. The intraobserver, interobserver, internal consistency of flow measurements, and consistency with conventional MRI were then evaluated with Pearson correlation and Bland-Altman analysis. Results Triplicate measurements of blood flow from 4D-PC were highly consistent, particularly at the aortic and pulmonary valves (cv 2–3%). Flow measurements were reproducible by a second observer (ρ = 0.986–0.999). Direct measurements of shunt volume from anomalous veins and intracardiac shunts matched indirect estimates from the outflow valves (ρ = 0.966). Measurements of shunt fraction using 4D-PC using any approach were more consistent with ventricular volumetric displacements than conventional 2D-PC (ρ = 0.972–0.991 versus 0.929). Conclusion Shunt flow may be reliably quantified with 4D-PC MRI, either indirectly or with detailed delineation of flow from multiple shunts. The 4D-PC may be a more accurate alternative to conventional MRI.

Sparse Reconstruction Techniques in Magnetic Resonance Imaging

“…The use of sparse reconstructions has also been explored for improving 4D flow or phase contrast imaging 111 , to evaluate valvular insufficiency, improve accuracy in delineating shunt pathology, assess anomalous flow in pulmonary veins, and visualize hemodynamics in congenital heart disease 112–116 . Sparse reconstructions have been used to obtain single breath-hold characterization of portal flow 117 and can yield improved vessel conspicuity while retaining accuracy of quantification of portal flow 118 .…”

Left ventricular global longitudinal strain in bicupsid aortic valve patients: head-to-head comparison between computed tomography, 4D flow cardiovascular magnetic resonance and speckle-tracking echocardiography

“…4D flow CMR allows for comprehensive post-hoc evaluation of blood flow patterns by 3D blood flow visualization and quantification of flow parameters [ 18 ]. Previous studies have shown that quantification of ventricular volume and function can be accomplished with 4D flow MRI with precision and inter-observer agreement comparable to that of SSFP cine imaging [ 19 , 20 ]. Strain analysis would be a valuable additional feature of 4D flow CMR, as this would allow for integrative analysis of flow and function in one sequence.…”

Accelerated aortic 4D flow cardiovascular magnetic resonance using compressed sensing: applicability, validation and clinical integration

“…Acceleration techniques based on compressed sensing (CS) − often combined with non-Cartesian sampling, with and without exploitation of spatio-temporal correlations − have also been applied to 4D flow CMR achieving similar acceleration rates [12–15]. One major disadvantage of most proposed CS techniques is their relatively long off-line reconstruction time, reportedly being in the range of 45 to 60 min [12, 13, 16].…”