Scheidegger M B, Maier S E, Boesiger P
Institute of Biomedical Engineering and Medical Informatics, University of Zurich, Switzerland.
Magn Reson Imaging. 1991;9(4):517-24. doi: 10.1016/0730-725x(91)90038-n.
The FID-Acquired-Echo sequence (FAcE) is a magnetic resonance imaging technique using fractional-echo acquisitions, with sequential separate sampling of the right and left k-space half planes. It reduces the minimal echo times by about a factor of two, compared to conventional full-(gradient)-echo sampling schemes. With this sequence, implemented on a commercial 1.5 Tesla whole body system, high resolution images are acquired with typical echo times between 3 and 4.5 msec. Using short echo times the signal dephasing caused by velocity and higher order spin motion is reduced. Further, due to the modified sampling scheme, the sequence exhibits, for triggered studies, partially a compensation of motion-induced phase shifts in the frequency-encoding direction. Thus, the sequence offers an alternative means for the reduction of motion-induced image artefacts to the use of flow compensating gradients, which usually makes a sequence more sensitive to higher order motion and introduces further eddy currents. Besides potential application for imaging of nuclei and tissues with short T2 relaxation times, and non-ECG-triggered in-flow angiography, the main application seems to be triggered-phase contrast imaging with focus on quantitation of blood flow. Its usefulness is largest in cases with irregular flow patterns, where considerable in-plane flow occurs.
FID采集回波序列（FAcE）是一种磁共振成像技术，采用分数回波采集，对左右k空间半平面进行顺序独立采样。与传统的全（梯度）回波采样方案相比，它将最小回波时间减少了约一半。在商用1.5特斯拉全身系统上实现该序列后，可采集到典型回波时间在3至4.5毫秒之间的高分辨率图像。使用短回波时间可减少由速度和高阶自旋运动引起的信号失相。此外，由于采样方案的改进，对于触发研究，该序列在频率编码方向上部分地表现出对运动诱导相移的补偿。因此，该序列为减少运动诱导图像伪影提供了一种替代方法，以替代使用流动补偿梯度，流动补偿梯度通常会使序列对高阶运动更敏感并引入更多涡流。除了对具有短T2弛豫时间的核和组织成像以及非心电图触发的流入血管造影的潜在应用外，其主要应用似乎是专注于血流定量的触发相位对比成像。在血流模式不规则且存在相当大平面内血流的情况下，其效用最大。
