关键词: 锥形束CT, 头颅侧位片, 二维图像, 颈椎骨龄, 颈椎骨龄定量分析法

Abstract: BACKGROUND: Traditional lateral cephalometric radiographs always suffer from some problems, such as magnification distortion, left and right overlap inconsistency and so on, while the cone-beam CT can truly display the three-dimensional structure of the craniofacial region. Performing three-dimensional reconstruction of cone-beam CT and then transforming the cone-beam CT in the selected area into the two-dimensional image can make the overlap between the left and right sides consistent and reduce the influence of surrounding tissue structures. 
OBJECTIVE: To explore the consistency of quantitative analysis of cervical vertebral bone age between two kinds of cone-beam CT transformed two-dimensional images with different integrated thicknesses and traditional lateral cephalometric radiographs.  
METHODS: The cone-beam CT and lateral cephalometric radiograph data of 118 adolescent orthodontic patients were collected. Firstly, the cone-beam CT image was reconstructed in 3D imaging software. After reconstruction, two types of cone-beam CT images with different integrated thicknesses were selected in the sagittal interface and transformed into two-dimensional images, which were named ICB-1 and ICB-2, respectively. The Zhibeiyun system was used to measure and calculate the angle between the concave base of the second cervical vertebra and the lower edge of the vertebral body (@2), the ratio of the third cervical spine to the posterior height (AH3/PH3), the ratio of height to width of the fourth cervical spine (H4/W4) in lateral cephalometric radiograph, ICB-1, ICB-2 and the cervical vertebral bone age. After an interval of two weeks, 20 adolescents were randomly selected to repeat the above measurements. The intraclass correlation coefficient (ICC) method was used to evaluate the repeatability of the three images in measuring cervical bone age. Paired t-test was used to analyze the consistency of cervical bone age measurements between the three images. The Kappa test was used to analyze the consistency of cervical vertebral bone age staging assessment between the three images. 
RESULTS AND CONCLUSION: (1) ICC of AH3/PH3 in the lateral cephalometric radiograph group was < 0.9, and the ICC of other measurement items in each group was > 0.9. (2) Paired t-test results showed that there were statistical differences in AH3/PH3 and H4/W4 between the ICB-1 group and lateral cephalometric radiograph group and between the ICB-1 group and ICB-2 group (P < 0.05), and there were no statistically significant differences in the other items between the three groups (P > 0.05). (3) The Kappa test results showed that the Kappa coefficients of the two groups were all more than 0.8 according to the staging of cervical vertebral bone age in three groups (P < 0.001). (4) It is indicated that the repeatability of ICB-1 and ICB-2 in the measurement of cervical vertebral bone age is better than that of lateral cephalometric radiographs. Lateral cephalometric radiographs, ICB-1 and ICB-2 have good consistency in the measurement of cervical vertebral bone age, but considering the integrity of cervical vertebra structure, ICB-2 is more suitable for quantitative analysis of cervical vertebral bone age than ICB-1.

Key words: cone-beam CT, lateral cephalometric radiograph, two-dimensional image, cervical vertebral bone age, quantitative cervical vertebral maturation method