Background

Four-dimensional (4D) flow magnetic resonance imaging (MRI) sequences with advanced parallel imaging have the potential to reduce scan time with equivalent image quality and accuracy compared with standard two-dimensional (2D) flow MRI. We compared 4D flow to standard 2D flow sequences using a constant and pulsatile flow phantom at 3 T.

Methods

Two accelerated 4D flow sequences (GRAPPA2 and k-t-GRAPPA5) were evaluated regarding the concordance of flow volumes, flow velocities, and reproducibility as well as dependency on measuring plane and velocity encoding (V_enc). The calculated flow volumes and peak velocities of the phantom were used as reference standard. Flow analysis was performed using the custom-made software “Bloodline”.

Results

No significant differences in flow volume were found between the 2D, both 4D flow MRI sequences, and the pump reference (p = 0.994) or flow velocities (p = 0.998) in continuous and pulsatile flow. An excellent correlation (R = 0.99–1.0) with a reference standard and excellent reproducibility of measurements (R = 0.99) was achieved for all sequences. A V_enc overestimated by up to two times had no impact on flow measurements. However, misaligned measuring planes led to an increasing underestimation of flow volume and mean velocity in 2D flow accuracy, while both 4D flow measurements were not affected. Scan time was significantly shorter for k-t-GRAPPA5 (1:54 ± 0:01 min, mean ± standard deviation) compared to GRAPPA2 (3:56 ± 0:02 min) (p = 0.002).

Conclusions

Both 4D flow sequences demonstrated equal agreement with 2D flow measurements, without impact of V_enc overestimation and plane misalignment. The highly accelerated k-t-GRAPPA5 sequence yielded results similar to those of GRAPPA2.

中文翻译：

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在3 T验证两个加速的4D流MRI序列：一项幻像研究。

背景

与标准二维（2D）流MRI相比，具有高级并行成像的四维（4D）流磁共振成像（MRI）序列有可能以相同的图像质量和准确性减少扫描时间。我们在3 T下使用恒定且搏动的流动体模将4D流动与标准2D流动序列进行了比较。

方法

对两个加速的4D流序列（GRAPPA2和kt -GRAPPA5）进行了评估，涉及流量，流速和重现性以及对测量平面和速度编码（V _enc）的一致性。计算的体模的流量和峰值速度用作参考标准。使用定制软件“ Bloodline ”进行流量分析。

结果

在2D，4D流MRI序列和 连续和脉动流中的泵参考（p  = 0.994）或流速（p = 0.998）之间，流量没有显着差异。 对于所有序列，均获得了 与参考标准品的极佳相关性（R = 0.99–1.0）和出色的测量重现性（R = 0.99）。一个V _ENC高达两倍高估对流量测量没有影响。但是，未对齐的测量平面会导致对2D流量精度中的流量和平均速度的低估增加，而两个4D流量测量均不受影响。kt的扫描时间明显缩短-GRAPPA5（1:54±0:01分钟，平均值±标准差）与GRAPPA2（3:56±0:02分钟）相比（p  = 0.002）。

结论

两种4D流量序列均与2D流量测量结果具有相同的一致性，而没有V _enc高估和平面未对准的影响。高度加速的kt -GRAPPA5序列产生的结果与GRAPPA2相似。