Comparison of 2D and 4D Flow MRI in Neonates Without General Anesthesia

BACKGROUND: Neonates with critical congenital heart disease require early intervention. Four‐dimensional (4D) flow may facilitate surgical planning and improve outcome, but accuracy and precision in neonates are unknown. PURPOSE: To 1) validate two‐dimensional (2D) and 4D flow MRI in a phantom and investigate the effect of spatial and temporal resolution; 2) investigate accuracy and precision of 4D flow and internal consistency of 2D and 4D flow in neonates; and 3) compare scan time of 4D flow to multiple 2D flows. STUDY TYPE: Phantom and prospective patients. POPULATION: A total of 17 neonates with surgically corrected aortic coarctation (age 18 days [IQR 11–20]) and a three‐dimensional printed neonatal aorta phantom. FIELD STRENGTH/SEQUENCE: 1.5T, 2D flow and 4D flow. ASSESSMENT: In the phantom, 2D and 4D flow volumes (ascending and descending aorta, and aortic arch vessels) with different resolutions were compared to high‐resolution reference 2D flow. In neonates, 4D flow was compared to 2D flow volumes at each vessel. Internal consistency was computed as the flow volume in the ascending aorta minus the sum of flow volumes in the aortic arch vessels and descending aorta, divided by ascending aortic flow. STATISTICAL TESTS: Bland–Altman plots, Pearson correlation coefficient (r), and Student's t‐tests. RESULTS: In the phantom, 2D flow differed by 0.01 ± 0.02 liter/min with 1.5 mm spatial resolution and −0.01 ± 0.02 liter/min with 0.8 mm resolution; 4D flow differed by −0.05 ± 0.02 liter/min with 2.4 mm spatial and 42 msec temporal resolution, −0.01 ± 0.02 liter/min with 1.5 mm, 42 msec resolution and −0.01 ± 0.02 liter/min with 1.5 mm, 21 msec resolution. In patients, 4D flow and 2D flow differed by −0.06 ± 0.08 liter/min. Internal consistency in patients was −11% ± 17% for 2D flow and 5% ± 13% for 4D flow. Scan time was 17.1 minutes [IQR 15.5–18.5] for 2D flow and 6.2 minutes [IQR 5.3–6.9] for 4D flow, P < 0.0001. DATA CONCLUSION: Neonatal 4D flow MRI is time efficient and can be acquired with good internal consistency without contrast agents or general anesthesia, thus potentially expanding 4D flow use to the youngest and smallest patients. EVIDENCE LEVEL: 1 TECHNICAL EFFICACY: Stage 2