P6114D flow CMR vs. 2D cine PC-CMR for flow volume quantification in congenital heart disease

Abstract

Background Two-dimensional cine phase-contrast cardiovascular magnetic resonance (2D cine PC-CMR) is arguably the gold-standard for quantification of blood flow volumes in patients with congenital heart disease (CHD). However, accurate planning and performing of multiple 2D acquisitions during one CMR scan is very time-consuming and can be challenging in patients with CHD. Four-dimensional (4D) flow CMR allows easy acquisition of a single three-dimensional (3D) volume and retrospective quantification of flow volume in any vessel or plane of interest, thus overcoming many of the difficulties of 2D cine PC-CMR. Purpose We sought to compare the flow volumes in major blood vessels and the internal consistency of the measurements between 2D cine PC-CMR and 4D flow CMR in patients with CHD. Methods Patients with CHD who had both 2D cine PC-CMR and 4D flow CMR acquisitions were retrospectively identified. The 2D scans were acquired during free breathing with 2 averages. The 4D acquisitions were performed using a free-breathing, prototype navigator-gated 3D cine phase-contrast CMR sequence with three-directional velocity-encoding. Blood flow measurements in the ascending aorta (AA), main pulmonary artery (MPA), superior vena cava (SVC), descending aorta (DA), right pulmonary artery (RPA) and left pulmonary artery (LPA), as well as the Qp:Qs (MPA/AA flow) were compared between 2D cine PC-CMR and 4D flow CMR using the Bland-Altman plot analysis. The internal consistency of the measurements was evaluated by correlation of MPA vs. RPA + LPA and MPA vs. AA flows on 2D cine PC-CMR, and MPA vs. RPA + LPA, MPA vs. right pulmonary veins (RPV)+left pulmonary veins (LPV), RPA + LPA vs. RPV + LPV and MPA vs. AA flows on 4D flow CMR. Results 31 patients were included for analysis. The duration of individual 2D acquisitions was 1-3 minutes, while the duration of the 4D acquisitions was 5-10 minutes. There was significant correlation between flows on both 2D cine PC-CMR (MPA vs. RPA + LPA, r = 0.87, p < 0.0001; MPA vs. AA, r = 0.62, p < 0.01) and 4D flow CMR (MPA vs. RPA + LPA, r = 0.91, p< 0.01E-10; MPA vs. RPV + LPV, r = 0.79, p < 0.000001; RPA + LPA vs. RPV + LPV, r = 0.75, p < 0.000001; MPA vs. AA, r = 0.72, p < 0.0001). There was significant agreement between 2D and 4D measurements for MPA (bias -0.22 l/min/m2, CI -0.45, 0.01), RPA (bias -0.12, CI -0.27, 0.02) and LPA (bias -0.10, CI -0.22, 0.02) flows, as well as Qp:Qs (bias -0.03, CI -0.12, 0.06), but not for AA (bias -0.22, CI -0.34, -0.10), SVC (bias -0.14, CI -0.27, -0.02) and DA (bias -0.37, CI -0.49, -0.25) flows. Conclusions Compared to standard 2D cine PC-CMR, 4D flow CMR allows faster and more comprehensive quantification of blood flow volumes in patients with CHD. The internal consistency of measurements is excellent with both techniques, but is greater with 4D flow CMR. There is significant agreement between 2D and 4D measurements for MPA, RPA and LPA flows, as well as Qp:Qs, but not for AA, SVC and DA flows.