Measurement of thymus in normal fetuses using two- and three-dimensional ultrasound

, ， ,

(Department of Ultrasound, Obstetrics and Gynecology Hospital Affiliated toNanjing Medical University， Nanjing 210004， China)

Measurement of thymus in normal fetuses using two- and three-dimensional ultrasound

WANGYongmei,WUYun*，CAOLi,ZHAWen

(DepartmentofUltrasound,ObstetricsandGynecologyHospitalAffiliatedtoNanjingMedicalUniversity，Nanjing210004，China)

Objective To evaluate the best indicator for detecting normal fetal thymus using prenatal two-dimensional (2D) and three-dimensional (3D) ultrasound. Methods During 22—39 weeks of gestational ages， the 2D and 3D ultrasound measurement of thymus were performed on a total of 360 normal singleton fetuses. The transverse diameter, anterior-posterior diameter, perimeter and area of fetal thymus were detected by 2D ultrasound. The volume of fetal thymus were obtained by 3D ultrasound. Regression analysis was used to explore the relationship between gestational age and different measurement indicators. And theSteiger'sttext was done to compare the correlations. Results The transverse diameter, anterior-posterior diameter, perimeter, area and volume of fetal thymus increased with gestational age in linear fashion. The best equations of regression were as follows： Transverse diameter (cm)=-1.98+0.16×gestational age (week), antero posterior diameter (cm)=-0.80+0.08×gestational age (week), perimeter (cm)=-5.00+0.42×gestational age (week), area (cm2)=-1.49+0.35×gestational age (week), volume (ml)=-2.12+0.45×gestational age (week) (allP<0.01). TheSteiger'sttest showed that the correlation between gestational age and thymus volume was higher than other indicators (P<0.01). Conclusion For normal fetuses of 22—39 gestational weeks， 3D ultrasound measurement of fetal thymus volume is the best indicator to evaluate the developmental state of thymus.

Ultrasonography， prenatal； Thymus gland； Fetus

表1 孕22～39周胎儿胸腺超声测量值

胸腺是人体重要的免疫器官。近年来，胎儿胸腺发育不良与发生其他器官畸形等相关疾病的相关性受到广泛关注。高分辨率超声可清晰显示中孕期以后的胎儿胸腺，为产前超声评估胎儿胸腺发育并诊断胎儿胸腺发育不良提供了一种便捷、有效的方法[1]。本研究拟应用二维、三维超声对孕22～39周正常胎儿胸腺进行测量，计算不同孕周胎儿胸腺各径线长度及胸腺体积，并从中筛选出评估胎儿胸腺发育情况的最佳指标，以期为临床诊断胎儿胸腺发育不良及相关疾病提供可靠的参考依据。

1 资料与方法

1.1一般资料 选取2013年4月—2016年2月于我院接受产检的孕妇360名，年龄20～40岁，平均(29.0±4.9)岁，孕22～39周，每一孕周20名。均为单胎妊娠，孕早期超声检查胎儿大小符合孕周，孕中期胎儿系统超声筛查未见明确胎儿畸形。孕妇无妊娠合并症，如糖尿病、高血压等；孕期无胎膜早破。

1.2仪器与方法 采用Philips iU22彩色多普勒超声仪，二维超声应用C5-1探头，频率2.0～5.0 MHz，三维超声应用容积探头，频率1.0～6.0 MHz。首先行产科常规二维超声扫查，于胎儿胸部横断面的三血管-气管切面测量胎儿胸腺。胸腺前后径为胸骨后缘至大血管前缘的距离。胸腺横径为胸腺两端与胸骨和椎体连线相垂直的最大距离。应用轨迹球于声像图中描记胸腺边缘后，系统可自动获得胸腺周长和面积值。而后进行胎儿胸腺的三维采集，应用仪器自带软件包QLAB的GI3DQ进行分析，以三血管-气管切面显示胸腺……