八次激发SE-EPI在肝脏MRI的应用

目的；比较八次激发SE－EPI与呼吸门控FSE及SSFSE T2WI在肝脏的应用。方法：对14例志愿者及21例肝病患者行上腹部呼吸门控FSE及SSFSE和屏气八次激发SE－EPI扫描。所有T2WI序列均运用脂肪抑制技术。定量分析肝脏、病灶的信噪比及肝脏－病灶的对比噪声比，评价各序列的图像质量及伪影。结果：八次激发SE－EPI与SSFSE及FSE在肝脏及病灶信噪比，肝脏－病灶对比度噪声比和图像质量方面无明显差异（P＞0．05）。其磁敏感伪影较FSE及SSFSE重（P＜0．01），SE－EPI化学位移伪影与SSFSE及FSE相比无明显差别（P＞0．05）。SE－EPI及FSE运动伪影明显比SSFSE重（P＜0．01），但SE－EPI运动伪影与FSE相比无明显差别（P＞0．05）。SE－EPI与FSE及SSFSE的图像质量无明显差别（P＞0．05）。结论：八次激发SE－EPI能够在较短时间里提供较高质量的上腹部T2WI。被检查者在扫描时可自由平静呼吸或屏气，可作为肝脏T2WI的补充序列。

Application of eight-shot SE-EPI sequence in the hepatic MRI

Objective:To compare the performance of T2 weighted eight-shot spin-echo version of echo planar imaging (SE-EP1) .respiratory gating fast spin-echo (FSE) and single-shot fast spin echo (SSFSE) sequences for the detection of focal liver lesions. Methods: Breathhold eight-shot SE-EPI of the liver was evaluated in fourteen healthy volunteers and twenty-one patients,and the results were compared with respiratory-gating T2 weithted FSE and SSFSE. The fat-suppression technique was used in each sequence. The signal-to-noise ratio (SNR) of the liver and lesion and the contrast-to-noise ratio (CNR) of the lesion-to-liver were quantitatively analyzed,and the overall image quality and artifacts were also qualitatively analyzed. Results:Quantitatively,SE-EPI,SSFSE and FSE sequences showed non-significant differences(P>0. 05) in liver/lesion CNR,SNR of liver and lesion, the overall image quality and chemical shift artifacts. Susceptibility artifacts on SE-EPI were more than SSFSE and FSE. There were fewer motion and ghost artifacts on SE-EPI images compared to FSE images(P<0. 05). Conclusion; Eight-shot SE-EPI of the liver can provide superior high quality T2 weighted image in shorter acquisition times compared with respiratory-gating FSE and SSFSE. The patient can hold breath or respire freely during scanning. This technique may be useful in clinical application of hepatic MR imaging.