Precision, reproducibility and applicability of an undersampled multi-venc 4D flow MRI sequence for the assessment of cardiac hemodynamics

Background and purpose: For the assessment of cardiovascular blood flow, 2D flow (2D) and 4D flow with a single venc (4D Mono) are established techniques. The objective of this study was to validate a multi-venc 4D flow (4D Multi) sequence for the improved simultaneous assessment of arterial and venous flow in high and low flow conditions and to investigate the scan-rescan reproducibility and inter-observer variability of the novel sequence.

Methods: Eleven volunteers with no known heart condition (female: 6, mean age: 25.8 ± 9.1 years) and two patients with a Fontan circulation were examined using phase-contrast 2D and 4D flow MRI. Stroke volumes, maximum velocities, net flow curves and internal consistency were measured and compared between 2D, 4D Mono and 4D Multi. Additionally, scan-rescan and inter-observer variabilities were analyzed. Finally, qualitative visualization comparisons were performed.

Results: Bland-Altman analysis show a higher agreement in stroke volumes between 4D Multi and 2D (7 ± 11%) than 4D Mono and 2D (11 ± 24%). 4D Multi is more accurate than 4D Mono in measuring time-resolved net flow throughout the cardiac cycle and qualitative blood flow visualization of 4D Multi is more accurate in visualizing flow patterns revealing more details and less artifacts than 4D Mono. Scan-rescan reproducibility is higher in 4D Multi (-0.04 ± 4.5 ml) than 2D (2.1 ± 7.3 ml) and inter-observer variability is low in both techniques (2D: -0.4 ± 3.4 ml and 4D Multi: 0.4 ± 3.5 ml). Internal consistency was improved in volunteers and patients when using 4D Multi as compared to 4D Mono.

Conclusion: 4D Multi offers a comprehensive way to accurately quantify flow in arteries and veins both in high and low flow situations and to visualize detailed flow patterns. This technique is readily applicable in the clinical setting and has the potential to be beneficial in the clinical assessment of valvular and congenital heart diseases.