Wah Y M I, Chan L W D, Leung T Y, Fung T Y, Lau T K
Department of Obstetrics and Gynaecology, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong.
Ultrasound Obstet Gynecol. 2008 Dec;32(7):855-9. doi: 10.1002/uog.6125.
To study the deviation of presumed midsagittal sections of the fetal head from the true image plane, to compare whether certification (by The Fetal Medicine Foundation (FMF), UK) has an effect on the degree of this deviation, and to investigate the impact of imperfect midsagittal sections on nuchal translucency thickness (NT) measurement.
Eight sonographers, four of them FMF-certified (Group A) and the other four not (Group B), were asked to obtain image sections which they believed to represent true midsagittal sections of the fetal head and neck in five patients each. Three-dimensional volume datasets were acquired for subsequent analysis. The angle between the falx cerebri and the vertical axis was measured and the effect of this angle on NT measurement was assessed.
The mean angle of deviation was significantly lower among those who were FMF-certified (5.7 degrees vs. 14.7 degrees, P < 0.001). The 1.8% underestimation of NT by Group A was not statistically significant (P = 0.76), while in Group B the NT could not be measured when the angle of deviation was 14.7 degrees.
FMF-certified operators obtain a better midsagittal section compared with non-certified operators. The minor deviation from the true midsagittal section by certified operators has no significant effect on the value of NT measurement. This study could provide a model for operator training and auditing.
研究胎儿头部假定正中矢状切面与真实图像平面的偏差，比较认证（由英国胎儿医学基金会（FMF）进行）是否对这种偏差程度有影响，并调查不完美的正中矢状切面对头颈部透明带厚度（NT）测量的影响。
八名超声检查人员，其中四名获得FMF认证（A组），另外四名未获得认证（B组），要求他们分别为五名患者获取他们认为代表胎儿头部和颈部真实正中矢状切面的图像切片。采集三维容积数据集用于后续分析。测量大脑镰与垂直轴之间的角度，并评估该角度对NT测量的影响。
获得FMF认证者的平均偏差角度显著更低（5.7度对14.7度，P < 0.001）。A组对NT的低估1.8%无统计学意义（P = 0.76），而在B组中，当偏差角度为14.7度时无法测量NT。
与未获得认证的操作人员相比，获得FMF认证的操作人员能获得更好的正中矢状切面。获得认证的操作人员与真实正中矢状切面的微小偏差对NT测量值无显著影响。本研究可为操作人员培训和审核提供一个模型。
