半FOV匀场技术纠正FIESTA序列腹部磁敏感伪影的初步研究

A preliminary study on semi FOV shimming technique to reduce the magnetic susceptibility artifacts of the abdominal FIESTA sequence

目的:探讨快速稳态进动采集(fast imaging employing steady-state acquisition,FIESTA)序列腹部冠状位MRI成像时磁敏感伪影的形成机制,以及匀场技术对减少磁敏感伪影的应用价值。方法:在1.5T MRI,采用不同FOV匀场策略的FIESTA序列对患者行腹部冠状位扫描。以膈肌以下肝脏为ROI,对匀场后ROI部位伪影的改善效果进行评分,分析和比较不同匀场策略对于改善肝脏部位磁敏感伪影的差异。结果:1FIESTA序列腹部冠状位扫描时在膈肌附近易产生磁敏感伪影。2施加匀场之后可以改善伪影,半FOV匀场效果优于全FOV匀场效果(Z=-6.211,P<0.05)。结论:FIESTA序列腹部扫描时正确施加适当范围的局部匀场可以减少磁敏感伪影,提高图像质量。

Objective： To investigate the mechanism of magnetic susceptibility artifacts of the fast imaging employing steady- state acquisition （FIESTA） abdominal coronal MR imaging and the application value of the shimming technique to reduce the artifact. Methods：27 cases underwent FIESTA abdominal coronal MRI scanning with different field of view shimming strategies. We selected the liver under the diaphragm as the ROI and evaluated the artifacts reduction after different shimming. Resuits：It was easy to form magnetic susceptibility artifacts near the diaphragm in the FIESTA abdominal coronal MR imaging. The shimming technique could reduce the magnetic susceptibility artifacts. There was significant difference between the different FOV shimming strategies （Z=- 6.211, P〈0.05）. Conclusion：The appropriate shimming strategy can reduce the magnetic susceptibility artifacts on the FIESTA images.