不同分割阈值重建锥形束CT数字化牙模型的精度研究

Accuracy of digital models reconstructed by cone-beam CT under different segmentation thresholds

目的:比较不同分割阈值对锥形束CT(CBCT)重建数字化牙模型测量精度的影响。方法:选取20例需拔除智牙患者的CBCT,应用Mimics软件,根据不同灰度值(grey value,GV)进行阈值分割后,重建三维数字化模型。所有患者均取硅橡胶印模,灌制石膏模型。分别测量数字化模型和石膏模型上、下颌全牙列牙的近远中径。采用SPSS 16.0软件包中的配对t检验、散点图和组内相关系数(intraclass correlation coefficient,ICC),评估不同分割阈值对重建的CBCT数字化模型测量精度的影响。结果:不同分割阈值重建的CBCT数字化牙模型与石膏模型测量项目之间均数的差范围为-0.36~0.32 mm。以GV 1200、1400阈值分割后,重建的数字化模型测量值与石膏模型测量值无统计学差异(P>0.01),其余阈值重建的数字化模型测量值与石膏模型有统计学差异(P<0.01)。CBCT重建数字化模型与石膏模型的测量值ICC均>0.95,其中,GV1200阈值重建的数字化模型ICC最高,为0.995。结论:不同分割阈值对CBCT重建数字化牙模型的精度有一定影响,对不同结构的侧重也不同,临床上应加以选择调整。

PURPOSE: To compare the accuracy of digital models reconstructed by cone-beam CT(CBCT) under different segmentation thresholds(STs). METHODS: A total of 20 patients who had CBCT images for diagnostic purposes were included in this study. Three-dimensional digital models were reconstructed by CBCT scans using different STs(based on gray value(GV) from 200 to 1800,gap 200)with Mimics 15.01. Plaster models were obtained, and mesiodistal diameter of each tooth was measured in all models. Paired t test was used to evaluate the accuracy of the digital models in comparison to the plaster models. Scatter plots and intraclass correlation coefficient(ICC) were also used to evaluate the correlation between the models with SPSS 16.0 software package. RESULTS: The mean difference between digital models and plaster model was from-0.36 mm to 0.32 mm. There was no significant difference between the plaster model and the digital models reconstructed under ST GV 1200 and 1400(P>0.01). The measurements of digital models reconstructed under other STs were different from the plaster ones(P<0.01). ICCs between digital models and plaster model were all >0.95.CONCLUSIONS: The accuracy of CBCT reconstructed 3-dimensional digital model is influenced by different STs.Therefore, selection needs to be made in clinical application.