探讨数字断层融合技术层中心与图像变形的相关性

Assessment of correlation between layer center and image deformation in digital tomosynthesis

目的通过模型评价数字断层融合(DTS)技术层中心与图像变形的相关性。方法按左右(L-R)方向和头尾(C-C)方向均相距6cm将11个直径为13.5mm钢球排在同一平面。将实验模型固定在距检查床120mm高度处,变化Height值;变化实验模型高度,同时变化对应Height值;分别测量各钢球在L-R和C-C两个方向上的直径及C-C方向上的成像范围。结果采用Thickness++重建后,各钢球L-R方向上的直径无明显变形,C-C方向上的直径均变小,最大变形度约为2.96%,位于层中心的钢球变形度最小。在C-C方向上存在金属伪影,采用Thickness++(Metal)重建后金属伪影不明显,但钢球在L-R和C-C两个方向的直径均变小。实验模型越靠近床面,C-C方向上的成像范围越大。结论 DTS偏中心成像时,ROI图像会发生变形;采用Thickness++(Metal)重建能有效去除金属伪影。

Objective To observe the correlation between layer center and image deformation of digital tomosynehesis imaging by experimental model.MethodsEleven steel balls with diameter of 13.5 mm were placed in one plane,which were apart from 6 cm in the left to right（L-R） direction and cranial to caudal（C-C） direction.Height value was changed while the altitude of experimental model was fixed at 120 mm,and the altitude of experimental model and Height value were all changed,then the diameters of steel balls in L-R and C-C direction and the imaging range in the C-C direction were measured respectively.ResultsUsing ＂Thickness＋＋＂ reconstruction,the diameters of steel balls in L-R direction had no obvious distortion,while in C-C direction decreased.The maximum deformation was about 2.96%,and the deformation of steel balls in the layer center was the minimum.There were metal artifacts in C-C direction.Using ＂Thickness＋＋（Metal）＂ reconstruction,the metal artifacts were very weak,but the diameters of steel balls both in L-R and C-C direction decreased.The altitude of experimental model was more close to tabletop,and the imaging range in the C-C direction was larger.ConclusionAt the time of offset center imaging,deformation of ROI can happen.The metal artifacts can be removed effectively using ＂Thickness＋＋（Metal）＂ reconstruction.