目的 比较MRI快速平衡稳态采集(FIESTA)与单次激发快速自旋回波(SSFSE)序列诊断正常胎儿胸腺的价值.方法 对366胎正常胎儿行MR检查,采用FIESTA与SSFSE序列分别观察胎儿胸腺的解剖和MR表现,结果行Kappa和x2检验.于“三血管”层面测量胸腺面积(TA)、横径(TD),于矢状位测量上下径(SID),计算各孕周参数均值,拟合各参数与孕周的回归方程.结果 2名医师对FIESTA和SSFSE序列图像的评价结果一致性较好(Kappa=0.745、0.802,P均＜0.01),FIESTA和SSFSE序列图像显示清晰率分别为86.34％(632/732)和37.70％(276/732),差异有统计学意义(x2=367.520,P＜0.001).胎儿胸腺大小随孕周延长而增大,回归方程分别为:TA=-5.80+0.35×孕周(r=0.820,P＜0.01);TD=-14.59+1.63×孕周(r=0.817,P＜0.01);SID=9.63+1.44×孕周(r=0.778,P＜0.01).结论 FIESTA较SSFSE序列可更清晰地显示胎儿胸腺的细微结构及其轮廓,MRI能清晰地显示孕22周后的胎儿胸腺.%Objective To compare the diagnostic value of MR examination with fast imaging employing steady state acquisition (FIESTA) and single shot fast spin echo (SSFSE) sequences for normal fetal thymuses.Methods Totally 366 normal fetuses were examined using MRI with FIESTA and SSFSE sequences,and the anatomy and MR manifestations of thymuses were observed.Kappa analysis and x2 test were performed.The transverse area (TA) and transverse diameter (TD) were measured on the "three vessel" level,while the superoinferior diameter (SID) was measured on the sagittal level.The mean value of these parameters at different gestational were calculated,and the regression equations of each parameter and gestational age were fitted.Results Two doctors had good agreements with the images of FIESTA and SSFSE sequences (Kappa=0.745,0.802,both P＜0.01).The clear rate of FIESTA and SSFSE sequences was 86.34％ (632/732) and 37.70％ (276/732) respectively,and the differences were significant (x2 =367.520,P＜0.001).The thymic size increased with the gestational age,and the regression equations and correlation coefficients were:TA =-5.80 + 0.35 ×gestational (r=0.820,P＜0.01),TD=-14.59+1.63×gestational (r=0.817,P＜0.01),and SID=-9.63+1.44×gestational (r=0.778,P＜0.01).Conclusion The subtle structure and contour of fetal thymus showed with FIESTA sequence are clearer than those of SSFSE sequence.MRI can clearly show fetal thymus after 22 weeks of pregnancy.
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