From the *University Hospital Schleswig-Holstein, Campus Lübeck, Clinic for Radiology and Nuclear Medicine, Lübeck, Germany; Departments of †Radiology, ‡Medical Physics, §Biomedical Engineering, and ∥Medicine, University of Wisconsin-Madison, Madison, WI.
Invest Radiol. 2013 Dec;48(12):819-25. doi: 10.1097/RLI.0b013e31829a4f2f.
The objective of this study was to validate radially undersampled 5-point velocity-encoded time-resolved flow-sensitive magnetic resonance imaging (MRI) ("PC-VIPR", phase contrast vastly undersampled imaging with isotropic resolution projection reconstruction magnetic resonance) for the quantification of ascending aortic (AAO) and main pulmonary artery (MPA) flow in vivo.
Data from 18 healthy volunteers (41.6 ± 16.2 years [range, 22-73 years]; body mass index, 26.0 ± 3.5 [19.1-31.4]) scanned at 3 T with a 32-channel coil were included. The left and right ventricular stroke volumes calculated from contiguous short-axis CINE-balanced steady state free precession (CINE-bSSFP) slices were used as the primary reference for cardiac output. Flow measured from 2-dimensional phase contrast MRI (2D-PC-MRI) in the AAO and the MPA served as the secondary reference. Time-resolved 4-dimensional flow-sensitive MRI (4D flow MRI) using PC-VIPR was performed with a velocity sensitivity of Venc = 150 cm/s reconstructed to 20 time frames at 1.4-mm isotropic spatial resolution. In 11 of 20 volunteers, phantom-corrected 4D flow MRI data were also assessed. Differences between methods of calculating the left ventricular and right ventricular cardiac output were assessed with the Bland-Altman analysis (BA, mean difference ±2SD). The QP/QS-ratio was calculated for each method.
Initially, PC-VIPR compared unfavorably with CINE-bSSFP (left ventricular stroke volume: 96.5 ± 14.4 mL; right ventricular stroke volume: 93.6 ± 14.0 mL vs 81.2 ± 24.3 mL [AAO] and 85.6 ± 25.4 mL [MPA]; P = 0.027 and 0.25) with BA differences of -14.6 ± 44.0 mL (AAO) and -9.0 ± 45.9 mL (MPA). Whereas phantom correction had minor effects on 2D-PC-MRI results and comparison with CINE-bSSFP, it improved PC-VIPR results: BA differences between CINE-bSSFP and PC-VIPR after correction were -1.4 ± 15.3 mL (AAO) and -4.1 ± 16.1 mL (MPA); BA comparison with 2D-PC-MRI improved to -12.0 ± 48.1 mL (AAO) and -2.2 ± 19.5 mL (MPA). QP/QS-ratio results for all techniques were within physiologic limits.
Accurate quantification of AAO and MPA flows with radially undersampled 4D flow MRI applying 5-point velocity encoding is achievable when phantom correction is used.
本研究旨在验证径向欠采样 5 点流速编码时间分辨流敏感磁共振成像（MRI）（“PC-VIPR”，相位对比超采样成像具有各向同性分辨率投影重建磁共振）用于活体升主动脉（AAO）和主肺动脉（MPA）流量的定量评估。
本研究纳入了 18 名健康志愿者（41.6±16.2 岁[范围，22-73 岁]；体重指数，26.0±3.5[19.1-31.4]）的 3T 扫描数据，采用 32 通道线圈。从连续短轴 CINE 平衡稳态自由进动（CINE-bSSFP）切片计算的左心室和右心室每搏量被用作心输出量的主要参考。从二维相位对比 MRI（2D-PC-MRI）在 AAO 和 MPA 中测量的流量作为次要参考。采用 PC-VIPR 进行时间分辨 4 维血流敏感 MRI（4D flow MRI），速度灵敏度为 Venc=150cm/s，重建到 1.4mm 各向同性空间分辨率的 20 个时间帧。在 20 名志愿者中的 11 名中，还评估了校正后体模的 4D flow MRI 数据。使用 Bland-Altman 分析（BA，平均差异±2SD）评估计算左心室和右心室心输出量的不同方法之间的差异。计算了每种方法的 QP/QS 比值。
最初，PC-VIPR 与 CINE-bSSFP 相比（左心室每搏量：96.5±14.4ml；右心室每搏量：93.6±14.0ml vs 81.2±24.3ml[AAO]和 85.6±25.4ml[MPA]；P=0.027 和 0.25）BA 差异为-14.6±44.0ml（AAO）和-9.0±45.9ml（MPA），差异不利。虽然体模校正对 2D-PC-MRI 结果和与 CINE-bSSFP 的比较影响较小，但它改善了 PC-VIPR 结果：校正后 CINE-bSSFP 与 PC-VIPR 之间的 BA 差异为-1.4±15.3ml（AAO）和-4.1±16.1ml（MPA）；与 2D-PC-MRI 的 BA 比较改善为-12.0±48.1ml（AAO）和-2.2±19.5ml（MPA）。所有技术的 QP/QS 比值结果均在生理范围内。
当使用体模校正时，径向欠采样的 4D flow MRI 应用 5 点流速编码可以准确地定量评估 AAO 和 MPA 流量。
