Department of Obstetrics and Gynecology, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong, China.
Ultrasound Obstet Gynecol. 2010 May;35(5):530-4. doi: 10.1002/uog.7574.
To determine the number of ultrasound examinations required to train sonographers to accurately measure the fetal frontomaxillary facial (FMF) angle at 11-13 weeks of gestation.
Eight sonographers accredited for nuchal translucency thickness (NT) measurement (and with different levels of experience) were trained to measure the fetal FMF angle using specially acquired three-dimensional (3D) volumes. Training was provided in cycles, and each cycle consisted of a training period on 20 randomly selected cases followed by an examination using 10 randomly selected cases. During training, the sonographer was informed of the true FMF angle value after each FMF angle measurement on a case-by-case basis. During examination, the difference between the measured and the true values of the FMF angle (i.e. the delta angle) was calculated. A measurement was considered accurate if the delta angle was less than 5 degrees . The sonographer was considered to be competent and the training finished if all 10 examination cases satisfied this criterion. Otherwise, the sonographer would undergo further cycles of training-examination, until he/she became competent.
The number of training cases required for a sonographer to become competent was 40 for two sonographers, 60 for one, 80 for one, 100 for two, 120 for one and 140 for one, with a median of 90. The median number of failed cases reduced from 2.5 (out of 10) at the first cycle to 0 by the 7(th) cycle. As training cycles increased, the mean angle deviation and measurement time required both reduced significantly. The average delta angle of the passing examination cycle was 2.06 +/- 1.40 degrees . The number of training cases required to become competent in FMF angle measurement was 40 for the two most experienced trainees and 80, 120 and 140 for the three least experienced ones.
We have demonstrated that competence in FMF angle measurement was achieved after a median number of 90 cases, with a range of up to 140. The number required was substantially lower, at 40 cases, among those with extensive experience of NT measurement.
确定培训超声医师准确测量 11-13 孕周胎儿额上颌（FMF）角所需的超声检查次数。
8 名接受过颈项透明层（NT）测量认证（且经验水平不同）的超声医师接受了使用专门采集的三维（3D）容积测量胎儿 FMF 角的培训。培训分为循环进行，每个循环包括在 20 个随机选择的病例上进行培训期，然后在 10 个随机选择的病例上进行检查。在培训期间，在每个病例的 FMF 角测量后，会逐例告知超声医师 FMF 角的真实值。在检查期间，计算 FMF 角的测量值与真实值之间的差值（即 delta 角）。如果 delta 角小于 5 度，则认为测量准确。如果所有 10 个检查病例都满足此标准，则认为超声医师有能力胜任，培训结束。否则，超声医师将进行更多的培训-检查循环，直到有能力胜任为止。
对于两名超声医师，成为有能力胜任的超声医师所需的培训病例数为 40，对于一名超声医师为 60，对于一名超声医师为 80，对于两名超声医师为 100，对于一名超声医师为 120，对于一名超声医师为 140，中位数为 90。在第一个循环中，失败病例的中位数从 2.5（10 个中的 2.5）减少到第 7 个循环的 0。随着培训循环的增加，平均角度偏差和所需的测量时间都显著降低。通过检查周期的平均 delta 角为 2.06 +/- 1.40 度。在 FMF 角测量方面，两名经验最丰富的受训者需要 40 个培训病例，而经验最少的三名受训者分别需要 80、120 和 140 个培训病例。
我们已经证明，在中位数为 90 例、范围高达 140 例的情况下，可以实现 FMF 角测量的能力。在那些有大量 NT 测量经验的人当中，所需的数量要低得多，为 40 例。
