The wide availability, low radiation dose and short acquisition time of Cone-Beam CT (CBCT) scans make them an attractive source of data for compiling databases of anatomical structures. However CBCT has higher noise ...The wide availability, low radiation dose and short acquisition time of Cone-Beam CT (CBCT) scans make them an attractive source of data for compiling databases of anatomical structures. However CBCT has higher noise and lower contrast than helical slice CT, which makes segmentation more challenging and the optimal methods are not yet known. This paper evaluates several methods of segmenting airway geometries (nares, nasal cavities and pharynx) from typical dental quality head and neck CBCT data. The nasal cavity has narrow and intricate passages and is separated from the paranasal sinuses by thin walls, making it is susceptible to either over- or under-segmentation. The upper airway was split into two: the nasal cavity and the pharyngeal region (nasopharynx to larynx). Each part was segmented using global thresholding, multi-step level-set, and region competition methods (the latter using thresholding, clustering and classification initialisation and edge attraction techniques). The segmented 3D surfaces were evaluated against a reference manual segmentation using distance-, overlap- and volume-based metrics. Global thresholding, multi-step level-set, and region competition all gave satisfactory results for the lower part of the airway (nasopharynx to larynx). Edge attraction failed completely. A semi-automatic region-growing segmentation with multi-thresholding (or classification) initialization offered the best quality segmentation. With some minimal manual editing, it resulted in an accurate upper airway model, as judged by the similarity and volumetric indices, while being the least time consuming of the semi-automatic methods, and relying the least on the operator’s expertise.展开更多
Aim To investigate the relationship between the positioning of the lower central incisor and physical morphology of the surrounding alveolar bone. Methodology Thirty-eight patients （18 males, 20 females）, with mean ...Aim To investigate the relationship between the positioning of the lower central incisor and physical morphology of the surrounding alveolar bone. Methodology Thirty-eight patients （18 males, 20 females）, with mean age of 13.4 years, were included in this study. As part of orthodontic treatment planning the patients were required to take dental Cone-beam CT （CBCT） covering the region of lower incisors, the sur- rounding alveolar bone and the mandibular symphysis. The cephalometric parameters were designed and measured to indicate the inclination of lower central incisor and physical morphology of the adjacent alveolar bone. Computer-aided descriptive statistical analysis was performed using SPSS 15.0 software package for Windows. A correlation analysis and a linear regression analysis between the incisor inclination and the alveolar bone morphology were performed. Results Significant positive correlations were found between the lower central incisor inclination and the morphological contour of the alveolar bone （P〈0.05）. The lower central incisor root apex was closer to the lingual alveolar crest when it was buccally inclined. Conclusion The morphology of the alveolar bone may be affected by incisal inclination.展开更多
目的:探讨CBCT在正畸临床诊断和治疗中的应用。方法:选取深圳市儿童医院口腔正畸科就诊的正畸患者25例(男12例,女13例),年龄11～16岁,平均13.8岁。入选病例均是因采用传统平片无法确诊,需要拍摄CBCT来辅助诊断和治疗的病例。CBCT影像使...目的:探讨CBCT在正畸临床诊断和治疗中的应用。方法:选取深圳市儿童医院口腔正畸科就诊的正畸患者25例(男12例,女13例),年龄11～16岁,平均13.8岁。入选病例均是因采用传统平片无法确诊,需要拍摄CBCT来辅助诊断和治疗的病例。CBCT影像使用NEW TOM VGi(QRs.r.l.Corp,Verona,Italy)大视野锥形束计算机体层X线摄影机拍摄,采用NEW TOMNNT软件进行图像的重建和分析。结果:CBCT可以清晰的显示阻生牙、异位牙的牙根形态、长度,弯曲牙根与牙长轴所成的角度;三维显示异位牙与邻牙的空间位置关系,邻牙的牙根吸收情况;上颌后牙牙根与上颌窦的位置关系等。结论:CBCT三维重建技术可大大提高正畸病例诊断的准确性,同时也为治疗计划的制定和实施提供了有利指导。展开更多
文摘The wide availability, low radiation dose and short acquisition time of Cone-Beam CT (CBCT) scans make them an attractive source of data for compiling databases of anatomical structures. However CBCT has higher noise and lower contrast than helical slice CT, which makes segmentation more challenging and the optimal methods are not yet known. This paper evaluates several methods of segmenting airway geometries (nares, nasal cavities and pharynx) from typical dental quality head and neck CBCT data. The nasal cavity has narrow and intricate passages and is separated from the paranasal sinuses by thin walls, making it is susceptible to either over- or under-segmentation. The upper airway was split into two: the nasal cavity and the pharyngeal region (nasopharynx to larynx). Each part was segmented using global thresholding, multi-step level-set, and region competition methods (the latter using thresholding, clustering and classification initialisation and edge attraction techniques). The segmented 3D surfaces were evaluated against a reference manual segmentation using distance-, overlap- and volume-based metrics. Global thresholding, multi-step level-set, and region competition all gave satisfactory results for the lower part of the airway (nasopharynx to larynx). Edge attraction failed completely. A semi-automatic region-growing segmentation with multi-thresholding (or classification) initialization offered the best quality segmentation. With some minimal manual editing, it resulted in an accurate upper airway model, as judged by the similarity and volumetric indices, while being the least time consuming of the semi-automatic methods, and relying the least on the operator’s expertise.
文摘Aim To investigate the relationship between the positioning of the lower central incisor and physical morphology of the surrounding alveolar bone. Methodology Thirty-eight patients （18 males, 20 females）, with mean age of 13.4 years, were included in this study. As part of orthodontic treatment planning the patients were required to take dental Cone-beam CT （CBCT） covering the region of lower incisors, the sur- rounding alveolar bone and the mandibular symphysis. The cephalometric parameters were designed and measured to indicate the inclination of lower central incisor and physical morphology of the adjacent alveolar bone. Computer-aided descriptive statistical analysis was performed using SPSS 15.0 software package for Windows. A correlation analysis and a linear regression analysis between the incisor inclination and the alveolar bone morphology were performed. Results Significant positive correlations were found between the lower central incisor inclination and the morphological contour of the alveolar bone （P〈0.05）. The lower central incisor root apex was closer to the lingual alveolar crest when it was buccally inclined. Conclusion The morphology of the alveolar bone may be affected by incisal inclination.
文摘目的:探讨CBCT在正畸临床诊断和治疗中的应用。方法:选取深圳市儿童医院口腔正畸科就诊的正畸患者25例(男12例,女13例),年龄11～16岁,平均13.8岁。入选病例均是因采用传统平片无法确诊,需要拍摄CBCT来辅助诊断和治疗的病例。CBCT影像使用NEW TOM VGi(QRs.r.l.Corp,Verona,Italy)大视野锥形束计算机体层X线摄影机拍摄,采用NEW TOMNNT软件进行图像的重建和分析。结果:CBCT可以清晰的显示阻生牙、异位牙的牙根形态、长度,弯曲牙根与牙长轴所成的角度;三维显示异位牙与邻牙的空间位置关系,邻牙的牙根吸收情况;上颌后牙牙根与上颌窦的位置关系等。结论:CBCT三维重建技术可大大提高正畸病例诊断的准确性,同时也为治疗计划的制定和实施提供了有利指导。
