锥形束CT转化头颅侧位片定点精确性的研究

目的 研究对比锥形束计算机断层扫描（Cone-beam computed tomography,CBCT）转化的头颅侧位片与传统头颅侧位片（Cephalogram,Ceph）的定点精度.方法 对20名需要正畸的患者（男7名,女13名,平均年龄18.8岁）进行锥形束CT扫描,同时拍摄Ceph作为对照.在InvivoDental 5.0软件中按统一条件将CBCT数据转化成头颅侧位片（Cephalogram from CBCT,CCB）.选择23个常用标志点,由三名操作者分别对CCB与Ceph进行定点,间隔进行两次.对CCB与Ceph上的定点误差,以及不同操作者之间的定点误差进行统计分析,采用方差分析与t检验.结果 三名操作者在CCB上定点的精度明显优于Ceph（P＜0.05）,19个定点的精度有8个点的定点误差差异有显著性（P＜0.05）.操作者之间的相关性CCB比Ceph好.操作者自身两次测量值重复性好,相关系数0.99.结论 CCB由于可以选择性生成单侧或双侧头颅侧位片,定点的精度普遍要优于Ceph,尤其是颅底点（Ba）,耳点（P）,眶点（O）,前鼻棘（ANS）点,上齿槽座点（A）,下颌角点（Go）,以及切牙及磨牙根尖点在CCB上的定点更精确.对于一些定点误差较大的点可能是由于在三维空间中点的定义还不明确.

Precision of cephalometric landmark identification from cone-beam computed tomography

Objective In this study, we compared the precision of landmark identification using cephalograms from cone-beam computed tomographic (CBCT) volumes and conventional lateral cephalograms (Ceph). Methods Twenty pre-orthodontic patients were radiographed with conventional Ceph and CBCT techniques. CBCT data was uploaded into InvivoDental software 5.0 to generate cephalograms(CCB). Three observers plotted 23 landmarks using computer displays of CCB and Ceph views during separate sessions. Absolute differences between CCB and Ceph of all observers were measured. The absolute difference between each observer was also measured. ANOVA and paired t tests were used to analyze variability differences. Results The difference of landmark identification between CCB and Ceph were significant at P＜0.05 calculations. 8 landmarks variability was statistically greater than Ceph views. The variability of CCB for each observer was consistently greater than in Ceph. The overall correlation of CCB and Ceph measurements was excellent at 0.99.Conclusions The CCB displays of CBCT volume images provide generally more precise identification than Ceph. More precise location of basion, porion, orbitale, ANS, A point, Gonion and tooth apex overcomes the problem of superimposition of these bilateral landmarks seen in Ceph. Greater variability of certain landmarks is probably related to inadequate definition of the landmarks in the third dimension.