Department of Orthodontics and Dentofacial Orthopedics, Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt.
Am J Orthod Dentofacial Orthop. 2011 Aug;140(2):157-65. doi: 10.1016/j.ajodo.2010.03.030.
The purpose of this research is to determine the accuracy and reliability of measurements obtained from 3-dimensional (3D) cone-beam computed tomography (CBCT) for different head orientations.
Stainless steel wires were fixed to a dry skull at different places. The skull was scanned by using CBCT in the centered and 5 other positions. Intraobserver and interobserver reliability tests were performed by using 6 landmarks identified on the virtual 3D skulls by 2 operators. Two methods were used to determine the accuracy of measurements on the virtual 3D skull scanned in different positions. In the first method, 12 linear distances were compared on the physical skull and the 3D virtual skull in the centered and the other scanning positions. In the second method, registration of each of the 5 positions on the centered position was done separately, and coordinates of 11 landmarks were identified in each position and compared with the centered position. Data gathered from the 2 methods were compared statistically.
Concordance correlation and Pearson correlation coefficients values were almost 0.9999 in all the comparisons denoting: (1) high intraobserver and interobserver reliability; (2) very high concordance between the physical skull and the CBCT centered-position measurements; (3) very high concordance between measurements of the centered position in relation to those obtained from the different skull positions; and (4) registration of the skulls in the different positions showed high concordance, with the highest values between the centered and off-centered positions, and the lowest with the complex position.
Accuracy and reliability of CBCT measurements are not affected by changing the skull orientation. Thus, the upper-lip and chin rests should not be considered absolute requirements during CBCT imaging if a stable head position is ensured.
本研究旨在确定在不同头部方位下，从三维（3D）锥形束 CT（CBCT）获得的测量值的准确性和可靠性。
将不锈钢丝固定在干颅骨的不同位置。使用 CBCT 对颅骨进行扫描，分别在中心位置和另外 5 个位置进行扫描。由 2 名操作人员在虚拟 3D 颅骨上识别 6 个标志点，进行观察者内和观察者间可靠性测试。使用两种方法确定在不同位置扫描的虚拟 3D 颅骨上的测量值的准确性。第一种方法是将物理颅骨和中心及其他扫描位置的 3D 虚拟颅骨上的 12 条线性距离进行比较。第二种方法是将每个位置分别与中心位置进行注册，在每个位置识别 11 个标志点的坐标，并与中心位置进行比较。对这两种方法获得的数据进行统计学比较。
在所有比较中，一致性相关和 Pearson 相关系数值几乎为 0.9999，表明：（1）观察者内和观察者间的可靠性非常高；（2）物理颅骨与 CBCT 中心位置测量值之间高度一致；（3）中心位置的测量值与从不同颅骨位置获得的测量值之间高度一致；（4）颅骨在不同位置的注册显示出高度的一致性，中心位置与偏离中心位置之间的一致性最高，而与复杂位置之间的一致性最低。
改变颅骨方位不会影响 CBCT 测量的准确性和可靠性。因此，如果能够确保头部位置稳定，则上唇和颏托在 CBCT 成像时不应被视为绝对要求。
