Department of Orthodontics, University Dental School of Erlangen-Nuremberg, Erlangen, Germany.
Eur J Orthod. 2012 Jun;34(3):276-86. doi: 10.1093/ejo/cjq190. Epub 2011 May 12.
The aim of this study was to investigate the repeatability and reproducibility of the placement of anthropological cephalometric landmarks on three-dimensional computed tomography (3D CT) cranial reconstructions derived from volume data sets. In addition, the influence of the observer's experience on the repeatability of landmark setting was also explored. Twenty patients without any craniofacial deformity (11 females and 9 males; age range 6.1-16 years) were selected retrospectively from CT volume data sets already available from 695 patients of Dental Clinic 3, Orthodontics of Erlangen University Hospital. The CT examination was performed with the SOMATOM Sensation64 (Siemens AG Medical Solutions, Erlangen, Germany). The program VoXim6.1 (IVS Solutions AG, Chemnitz, Germany) was used for 3D reconstruction of the volume data sets. A total of 28 landmarks were examined in the skeleton module of the program VoXim6.1. The randomly sorted data sets were analysed by two orthodontists and two postgraduate students. Each data set was analysed twice by each observer at an interval of 3 weeks. The analysis of variance regarding random effects was used to calculate the intraobserver and interobserver components of standard deviation (SD) of depiction of individual landmarks as measures of repeatability and reproducibility, respectively. Median intraserial SD and interserial SD of 0.46 mm (range: 0.14-2.00 mm) and 0.20 mm (range: 0.02-2.47 mm), respectively, were obtained depending on the landmark and plane. This study included systematic analysis of extreme values (outliers) in the assessment of the quality of measurements obtained. Descriptive statistics revealed qualitative differences in the depiction of different landmarks. The landmarks nasion and infradentale revealed a minor SD in all three spatial coordinates with the smallest SD for infradentale (SD = 0.18 mm) in the transverse plane. However, no systematic trend was identified with regard to the influence of the observer's level of experience affecting the repeatability of landmark positioning. Thus, the repeatability and reproducibility of placements of landmarks with 3D CT were found to be acceptable for a majority of anatomical positions.
本研究旨在探讨基于容积数据的三维 CT（3D CT）颅骨重建中人类学头影测量标志点的可重复性和再现性。此外，还探讨了观察者经验对标志点设置可重复性的影响。从已有的 695 例牙科 3 号诊所、埃尔朗根大学医院正畸科的 CT 容积数据中，回顾性选择了 20 名无颅面畸形的患者（11 名女性和 9 名男性；年龄 6.1-16 岁）。CT 检查采用西门子 SOMATOM Sensation64（德国西门子医疗解决方案公司）进行。使用 VoXim6.1 程序（IVS 解决方案公司，德国开姆尼茨）对容积数据进行三维重建。在 VoXim6.1 程序的骨骼模块中检查了 28 个标志点。将随机排序的数据由两名正畸医生和两名研究生进行分析。每位观察者在 3 周的间隔内对每个数据集进行两次分析。采用随机效应方差分析计算各标志点的个体描绘标准差（SD）的观察者内和观察者间分量，分别作为可重复性和再现性的度量。根据标志点和平面的不同，分别获得 0.46mm（范围：0.14-2.00mm）和 0.20mm（范围：0.02-2.47mm）的中位数内串行 SD 和外串行 SD。本研究包括对所获得测量质量的极值（异常值）进行系统分析。描述性统计显示，不同标志点的描绘存在定性差异。标志点鼻根点和下齿槽座点在所有三个空间坐标上的 SD 较小，其中在横断面上的下齿槽座点的 SD 最小（SD=0.18mm）。然而，没有发现观察者经验水平对标志点定位可重复性的影响存在系统趋势。因此，大多数解剖位置的 3D CT 标志点放置的可重复性和再现性是可以接受的。
