真实稳态进动快速成像T2^＊加权序列在胎儿MRI中的应用

目的:探讨真实稳态进动快速成像T2*加权序列在胎儿MRI中的临床应用价值.材料和方法:6例中、晚期孕程的孕妇行真实稳态进动快速成像(true FISP)T2*加权序列扫描,评价图像质量、模糊程度、正常胎儿器官显示、胎儿和母体异常的显示以及胎儿信噪比(SNR)及胎儿-孕妇腰椎椎体对比噪声比(F-L CNR)等,并与TSE序列T2WI进行比较.结果:与TSE序列T2WI相比,true FISP序列T2*WI可清楚显示胎头、胎儿肢体、胎儿脊柱、胎儿的脏器解剖结构以及母体子宫、胎盘、脐带等附属结构,胎儿和母体异常显示也较清晰,并能清晰显示灰、白质分界、脑回、脑髓鞘等结构.true FISP序列获得的图像其SNR以及F-L CNR均优于TSE序列.结论:真实稳态进动快速成像T2*加权序列能够清晰显示胎儿及母体的解剖结构,获得的图像具有较高的T2对比,可作为胎儿MR成像的常用序列.

Evaluation of True FISP T2* Weighted MR Imaging in the Fetus

Purpose: To evaluate the application of true fast imaging with steady state precession T2* weighted imaging in fetus. Materials and Methods: Six women with complicated pregnancies were scanned with true FISP T2* weighted imaging in a 1.5T super-conductive MR imaging unit. Images were analyzed with regard to image quality, degree of blurring, visualization of the normal fetal organs, and visualization of fetal and maternal abnormalities. Signal-noise ratio (SNR) of fetus and fetus-maternal lumbar vertebra contrast-noise ratio (F-L CNR) were evaluated. The results were compared with those from Turbo-SE T2 weighted imaging. Results: On true FISP sequences, visualization of the fetal brain, visceral organs (lung, kidney, and bladder), extremities, and umbilical cord were significantly better than on turbo spin-echo sequences (P<0.05). Pathologic processes including fetal abnormalities, placenta and maternal abnormalities were clearly seen on true FISP imaging. In the brain, the white matter-gray matter distinction, gyrus formation, and myelination of the brain were clearly revealed by the true FISP sequence. SNR and F-A CNR of true FISP sequences were better than those of turbo spin-echo sequences. Conclusion: MR imaging with a true FISP sequence allows clear fetal imaging with high T2 weighted contrast, which can be used as a standard sequence of fetal MR imaging.