Stefos T, Deter R L, Simon N V
Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, Texas 77030.
J Clin Ultrasound. 1989 Jun;17(5):319-25. doi: 10.1002/jcu.1870170503.
The effect of the time of the initial scan and the interval between the two scans needed for Rossavik growth model specification was evaluated in 20 normally growing fetuses. Based on systematic and random prediction errors, determined by comparing predicted values to measured values obtained after 27 weeks, menstrual age, optimal results for all parameters studied were obtained with an initial scan at 18 weeks and an interval of 6 weeks between scans. For one-dimensional parameters--head circumference (HC), abdominal circumference (AC), and femur diaphysis length (FDL)--similar results were obtained with an initial scan at 15 weeks and an interval of 3 weeks, but systematic overestimations were seen with 9-week intervals for HC. Studies with three-dimensional parameters--head cube, abdominal cube, and estimated weight--indicated that the timing of the initial scan was not critical, although less variability was seen with the initial scan at 18 weeks. However, the use of 3-week and 9-week intervals (instead of 6 weeks) produced significant systematic errors that varied with the parameter studied. These results suggest that Rossavik growth model specification is possible under a variety of conditions, but both the timing of the initial scan and the interval between scans must considered for each parameter.
在20例正常生长的胎儿中评估了初始扫描时间以及罗萨维克生长模型设定所需的两次扫描之间的间隔时间的影响。基于通过将预测值与孕27周后获得的测量值进行比较而确定的系统预测误差和随机预测误差，对于所有研究参数，在18周时进行初始扫描且扫描间隔为6周可获得最佳结果。对于一维参数——头围（HC）、腹围（AC）和股骨干长度（FDL）——在15周时进行初始扫描且间隔为3周可获得类似结果，但对于头围，9周的间隔会出现系统性高估。对三维参数——头部体积、腹部体积和估计体重——的研究表明，初始扫描时间并非关键因素，尽管在18周时进行初始扫描变异性较小。然而，使用3周和9周的间隔（而非6周）会产生显著的系统误差，且该误差会因所研究的参数而异。这些结果表明，在各种条件下罗萨维克生长模型设定都是可能的，但对于每个参数都必须考虑初始扫描时间和扫描间隔。
