CBCT金属伪影产生规律研究分析  

Configurations of metal-related artifacts in CBCT images:an in vitro experiment

作　　者：王家柱[1] 许来青[1] 王照五[1] 郭小龙[2] 陈卫彬[3] 吴宏新 

机构地区：[1]解放军总医院口腔医学中心放射科,技师北京100853 [2]解放军总医院口腔医学中心,硕士生北京100853 [3]解放军总医院器械处医疗工程技术中心,工程师北京100853 [4]北京朗视仪器有限公司,工程师北京100083

出　　处：《中华老年口腔医学杂志》2016年第4期230-236,共7页Chinese Journal of Geriatric Dentistry

摘　　要：目的:研究CBCT金属伪影产生的规律及特征,指导临床检查操作诊断,规避伪影对影像质量的影响,提高诊断水平。方法:将7根7mm直径一端是螺母的金属圆柱,长轴与X射线方向垂直,置于底部蜡板、下方40mm水、上方30mm空气的储槽中。使用Scanora 3D CBCT扫描重建。结果:观察伪影产生的相互关系,及圆柱与六棱螺母伪影的区别。分析:依据伪影产生大多是X线硬化、容积、空洞效应和衍射散射现象。发现伪影具有九大规律:一,圆形金属个体伪影呈X形放射状;二,多根金属体间产生空洞效应的低密度伪影;三,不同方向伪影相互叠加,重叠越多越强烈;四,不同位点的金属体伪影相互呈直线产生;五,伪影产生以平行于射线方向为主;六,伪影极少产生在空气中;七,金属体间低密度伪影边缘有相对增高的容积效应和散射伪影相伴;八,金属体间的位点,决定X形放射状伪影方向;九,产生伪影多少取决于金属体表形态,及相邻金属体个数和位置。临床常见牙冠、桩钉、牙胶等受形态位置影响,各种散射伪影并存。伪影散射方向随牙弓弧线角度变化,又与相邻高密度物体(包括牙体)组合位点有关。结论:试验发现在CBCT检查时,任何物质都会产生伪影,并具有九大规律。找到这些规律性,有助于CBCT检查时,指导影像工作者对存在有金属物体位的调整,规避伪影影响。并在影像阅读诊断中,充分认识伪影与正常解剖或是病理影像产生的区别,提高影像诊断水平。Objective： To investigate the configurations of metal-related artifacts in CBCT images in order to provide some evidence for differentiation between artifacts and real skeletal structures, and to avoid CBCT image interference by these kinds of artifacts. Methods： Cylinder-shaped iron bars（the number of bars ranging from 1 to 7, respectively, arranged according to certain geometrical shape） with a diameter of 15 millimeter were placed vertically on a wax plate in a round container with water. The part of iron bar immersed in water is 40 millimeter in length, while the part of iron bar above water is 20 millimeter in length. The water container with the wax plate and iron bars was scanned using Scanora 3D CBCT, then the CBCT image was reconstructed three-dimensionally. The configurations of artifacts in cross-sectional,coronal and sagittal views were recorded and analyzed. Results： The part of iron bars above water（in air） produced almost no artifacts, while iron bars within water produced strong artifacts comprising of X-shaped white crosses, black crosses and bands. When the number of iron bars were lower（i.e., below 3）, X-shaped white bands could be seen around each iron bar clearly. As the number of iron bars were greater and more than 3, the configurations of artifacts became more complex. Inaddition, the configurations of artifacts were associated with the shape of iron bars and the relative positioning of iron bars.Conclusions： Metal-related artifacts are more strong in water than in air. The configurations of artifacts differ according to the number of iron bars, shape of iron bars and their relative positioning.

关 键 词：CBCT 金属伪影 硬化效应 空洞效应 伪影产生规律 

分 类 号：R782[医药卫生—口腔医学] R816.98[医药卫生—临床医学]