Diagnostic value of fast imaging employing steady state acquisition and single shot fast spin echo sequences in diagnosis of normal fetal thymuses: Comparative study / 中国医学影像技术

ABSTRACT

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 wereTA =-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.