应用锥束计算机体层摄影术评价颅颌面的不对称

Evaluation of craniofacial asymmetry based on cone-beam CT image

锥束计算机体层摄影术（cone—beamcomputedtomography，CBCT）也可以称为锥束容积断层（conebeamvolumetrictomography，CBVT），与传统医学CT不同之处在于，其使用锥束射线单次旋转一次即可获得扫描对象的三维影像信息；而传统医学cT扫描方式是层扫描，即扇形射线束在一个层面内旋转,

SUMMARY Cone-beam CT （CBCT） was developed for the three-dimensional （3D） imaging of the max- illofacial area and has become popular in dentistry, orthodontics, and maxillofacial surgery. The advanta- ges of CBCT include less radiation exposure （than conventional CT）, less artifacts, and submillimeter spatial resolution. CBCT has been shown to produce accurate 3D images of the craniofacial region and a 1-to-1 image-to-reality ratio, which has greatly reduced errors of frontal eephalometry and improved our a- bility to diagnose asymmetry. Several new analyses to diagnose asymmetries on 3D images described in recent literature were reviewed, including 3D linear and angular measurements, mirror-image analysis （ superimposition of the mirror image of the anatomically correct part of the anatomy over the deformity） , 3 D cephalometric analysis based on constructing an individual coordinate system for each facial unit or el- ement （local coordinate systems） to differentiate them from entation）, and method of application of asymmetry indices the world coordinate system （whole head ori-entation）, and method of aoolication of asymmetry indices.