Objective

To evaluate an automatic correction method for velocity offset errors in cardiac 4D-flow acquisitions.

Materials and methods

Velocity offset correction was done in a plane-by-plane scheme and compared to a volumetric approach. Stationary regions were automatically detected. In vitro experiments were conducted in a phantom using two orientations and two encoding velocities (Venc). First- to third-order models were fit to the time-averaged images of the three velocity components. In vivo experiments included realistic ROIs in a volunteer superimposed to a phantom. In 15 volunteers, blood flow volume of the proximal and distal descending aorta, of the pulmonary artery (Qp) and the ascending aorta (Qs) was compared.

Results

Offset errors were reduced after correction with a third-order model, yielding residual phantom velocities below 0.6 cm/s and 0.4% of Venc. The plane-by-plane correction method was more effective than the volumetric approach. Mean velocities through superimposed ROIs of a volunteer vs phantom were highly correlated (r² = 0.96). The significant difference between proximal and distal descending aortic flows was decreased after correction from 8.1 to − 1.4 ml (p < 0.001) and Qp/Qs reduced from 1.08 ± 0.09 to 1.01 ± 0.05.

Discussion

An automatic third-order model corrected velocity offset errors in 4D-flow acquisitions, achieving acceptable levels for clinical applications.

中文翻译：

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使用三阶表面模型自动校正MRI中大血管和心脏的4D流动中的背景相位偏移

客观的

评估心脏4D流量采集中速度偏移误差的自动校正方法。

材料和方法

速度偏移校正是在逐平面方案中完成的，并与体积方法进行了比较。静止区域被自动检测到。使用两个方向和两个编码速度（Venc）在体模中进行了体外实验。一阶到三阶模型适合于三个速度分量的时间平均图像。体内实验包括叠加在体模上的志愿者的真实ROI。在15名志愿者中，比较了近端和远端降主动脉，肺动脉（Qp）和升主动脉（Qs）的血流量。

结果

用三阶模型校正后，可以减少偏移误差，从而产生低于0.6 cm / s和0.4％Venc的残留体模速度。逐平面校正方法比体积方法更有效。志愿者与体模通过ROI的平均速度高度相关（r ²  = 0.96）。校正后，近端和远端降主动脉血流之间的显着差异从8.1降低至-1.4 ml（p  <0.001），Qp / Qs从1.08±0.09降低至1.01±0.05。

讨论

自动三阶模型校正了4D流采集中的速度偏移误差，达到了临床应用可接受的水平。