Larsen M L, Naver K V, Kjaer M M, Jorgensen F S, Nilas L
Department of Obstetrics and Gynaecology, University Hospital Hvidovre, University of Copenhagen, Denmark.
Facts Views Vis Obgyn. 2015 Dec 28;7(4):203-209.
To evaluate the reproducibility of placental volume using three-dimensional ultrasound.
The VOCAL (Virtual Organ Computer-aided AnaLysis) technique involves rotating an image of an object along an established axis using predefined angles. This provides a number of sections to measure manually, resulting in the object being displayed with an estimated placental volume. Four predefined angles 30°, 15°, 9°, and 6°, creating 6, 12, 20 and 30 sections, respectively. Measurements of placenta volumes in 21 women with singleton pregnancies were performed at gestational age 11-14 weeks by a single consultant in Foetal Medicine and later processed by two observers. The intraobserver reproducibility between all four angles was calculated as the mean Coefficient of Variation. Interobserver reproducibility was assessed by Interclass Correlation Coefficient (ICC), Limits of Agreement (LOA) and illustrated in Bland-Altman plots.
There was no significant difference in intraobserver variability between the four angles, p = 0.19, but a trend towards a lower coefficient of variation with the smallest angle was observed. A high intraobserver reproducibility was found using the 6° angle (ICC = 0.918 (0.812 - 0.966) and 0.983 (0.960- 0.993), LOA = [-22.9- 22.5] and [-14.3 - 12.1]), but interobserver reproducibility showed a wide range of agreement (LOA = [-50.5- 34.8]), particularly in cases with u-shaped placentas.
The low interobserver reproducibility of VOCAL measurements of placentae requires significant differences between normal and abnormal cases if the technique should be implemented for clinical use.
使用三维超声评估胎盘体积的可重复性。
VOCAL（虚拟器官计算机辅助分析）技术包括使用预定义角度沿既定轴旋转物体图像。这提供了多个需手动测量的截面，从而得出显示有估计胎盘体积的物体。四个预定义角度分别为30°、15°、9°和6°，分别产生6、12、20和30个截面。由一名胎儿医学顾问在孕11 - 14周时对21名单胎妊娠女性的胎盘体积进行测量，随后由两名观察者进行处理。将所有四个角度之间的观察者内可重复性计算为变异系数均值。通过组内相关系数（ICC）、一致性界限（LOA）评估观察者间可重复性，并在布兰德 - 奥特曼图中进行展示。
四个角度之间的观察者内变异性无显著差异，p = 0.19，但观察到角度最小时变异系数有降低趋势。使用6°角时发现观察者内具有较高的可重复性（ICC = 0.918（0.812 - 0.966）和0.983（0.960 - 0.993），LOA = [-22.9 - 22.5]和[-14.3 - 12.1]），但观察者间可重复性显示出较宽的一致性范围（LOA = [-50.5 - 34.8]），尤其是在胎盘呈u形的情况下。
如果要将VOCAL胎盘测量技术用于临床，其观察者间可重复性较低，这要求正常与异常病例之间存在显著差异。
