目的 通过锥形束CT对颞下颌关节(TMJ)和耳屏、眼外眦等体表标志之间的空间位置关系进行定量测量,为拍摄TMJ锥形束CT精准临床摆位提供数据支持.方法 选择解放军总医院口腔科初诊拍摄大视野锥形束CT符合纳入标准的112例患者,其中男性35例,女性77例,年龄(25.6±9.8)岁(范围12～66岁).将患者的锥形束CT数据以".dicom"格式导入Mimics Medical 21.0软件进行三维重建,对选定的面部体表标志点和同侧TMJ分别在矢状位和冠状位上的投影点之间的相应距离进行测量,包括:正面观眼外眦至通过同侧髁突中心点垂线的水平距离(dx)、侧面观通过耳屏后缘最凸点的水平线至颞下颌关节窝最上点的垂直距离(dy1)、通过耳屏后缘最凸点的水平线至下颌乙状切迹的垂直距离(dy2)、侧面观耳屏后缘最凸点至通过同侧髁突中点垂线的水平距离(dz).并对左右侧及不同性别、年龄之间(12～18岁为青少年组,33例;＞18岁为成人组,79例)的测量值进行比较分析.对比采用探视图定位及使用体表标志点辅助定位拍摄TMJ小视野锥形束CT髁突中心点偏离视野中心的距离(探视图组,25例;体表标志辅助定位组,12～18岁及＞18岁各25例共计50例),验证本研究所获取的体表标志点的可靠性及稳定性.结果 共纳入112例患者的224侧TMJ,正面观,dx为(8.59±3.13)mm,左右两侧之间、男女之间的dx差异均无统计学意义(P＞0.05);青少年组dx[(7.43±3.02)mm]显著小于成人组[(9.07±3.06)mm](t=-3.68,P＜0.001).侧面观,dy1为(14.80±3.90)mm,左右两侧、男女之间以及不同年龄组之间的差异均无统计学意义(P＞0.05).dy2为(6.82±3.95)mm,青少年组dy2[(5.88±4.13)mm]显著小于成人组[(7.22±3.83)mm](t=-2.33,P=0.021),左右两侧及男女之间的差异均无统计学意义(P＞0.05).dz为(11.73±3.16)mm,左右两侧及男女之间的差异无统计学意义(P＞0.05);青少年组dz[(10.92±2.74)mm]显著小于成人组[(12.07±3.27)mm](t=-2.52,P=0.012).验证结果显示两种定位方法均能完整显示TMJ,探视图组髁突中心点偏离视野中心的距离[(8.84±3.79)mm]大于体表标志辅助定位组[(6.50±2.88)mm](t=4.20,P=0.032).结论 眼外眦及耳屏可以作为稳定的体表标志点辅助TMJ锥形束CT扫描定位.
Application of surface landmark positioning in assisting cone-beam CT scanning of temporomandibular joint
Objective To quantitatively measure the spatial relationship between the temporomandibular joint(TMJ)and surface landmarks such as the tragus and lateral canthus using cone-beam CT(CBCT),as to provide guidance for accurate positioning of CBCT scanning of the TMJ.Methods DICOM format data from 112 patients(35 males and 77 females with 224 TMJs)were included in this study.The patients were between 12 and 66 years old,with a mean age of(25.6±9.8)years and they underwent initial visits at the Department of Stomatology,General Hospital of Chinese PLA.CBCT images were imported into Mimics Medical 21.0 software for three-dimensional reconstruction.The distance between selected surface landmarks and corresponding projection points on the same side of the TMJ were measured in both the sagittal and coronal planes.In the frontal view,the distance from the lateral canthus to the perpendicular line passing through the center of the condyle(dx).In the lateral view,the vertical distance from the horizontal line through the rear edge convex of tragus to the roof of glenoid fossa(dy1);the vertical distance from the horizontal line through the rear edge convex of tragus to sigmoid notch(dy2);the distance from the tragus to the perpendicular line through the center of the condyle(dz).The results were compared between different genders and age groups(adolescent group aged 12 to 18 years,33 cases;adult group aged＞18 years,79 cases).To verify the reliability and stability of the body surface landmarks obtained in this study,a comparison was made between the use of scout view positioning and the auxiliary positioning method that utilizes body surface landmarks to capture the mandibular condyle in a small field of view CBCT of the TMJ(scout view group,25 cases;surface landmark-assisted positioning group,with 25 cases aged 12-18 years and 25 cases older than 18 years,totaling 50 cases),with regard to the deviation distance from the central point of the field of view to the central point of the mandibular condyle.Results A total of 112 patients with 224 TMJs were included in this study.In the frontal view,dxwas(8.59±3.13)mm,with no significant difference between the left and right sides,between males and females(P＞0.05).Notably,the dx in the adolescent group[(7.43±3.02)mm]was significantly smaller than that in the adult group[(9.07±3.06)mm](t=-3.68,P＜0.001).In the lateral view,dy1 was(14.80±3.90)mm,showing no significant difference between the left and right sides,males and females,or different age groups(P＞0.05).Similarly,dy2 was(6.82±3.95)mm,with no significant differences between the left and right sides or between males and females(P＞0.05).However,the dy2 in the adolescent group[(5.88±4.13)mm]was significantly smaller than that in the adult group[(7.22±3.83)mm](t=-2.33,P=0.021).Regarding dz,the measurement was(11.73±3.16)mm,with no significant difference between the left and right sides,between males and females(P＞0.05).Meanwhile,the dz in the adolescent group[(10.92±2.74)mm]was also significantly smaller than that in the adult group[(12.07±3.27)mm](t=-2.52,P=0.012).The verification results showed that both positioning methods could fully display the TMJ.The eccentricity in the scout view group[(8.84±3.79)mm]was slightly greater than that in the body surface landmark-assisted positioning group[(6.50±2.88)mm],and the difference between the two groups was statistically significant(t=4.20,P=0.032).Conclusions The TMJ can be accurately positioned using stable surface landmarks such as the tragus and lateral canthus for reference.
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