基于对数解调的递变能量CT成像方法  

CT imaging method with varying energy based on logarithm demodulation

作　　者：陈平[1] 韩焱[1] 潘晋孝[1] 

机构地区：[1]中北大学,仪器科学与动态测试教育部重点实验室,电子测试技术国家重点实验室,信息探测与处理山西省重点实验室,太原030051

出　　处：《物理学报》2015年第13期422-429,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:61171179,61227003,61301259,61471325);山西省自然科学基金(批准号:2015021099);高等学校博士学科点专项科研基金(批准号:20121420110006);山西省回国留学人员科研资助项目(批准号:2013-083)资助的课题~~

摘　　要：复杂结构件由于有效厚度差异大和成像系统动态范围受限,单一能量下的投影数据信息不完整,常用CT重建算法及不完全数据重建算法无法在数据缺失严重的情况,有效实现复杂结构件的CT重建.为此论文提出基于对数解调的递变能量CT成像方法.该方法在分析直接高动态CT成像所存在问题的基础上,提出利用对数变换压缩递变能量投影序列动态范围,并利用现有的基于图像灰度一致性的融合方法,计算融合加权系数,再经常规重建算法实现复杂构件的CT成像.论文并以某复杂仪表为对象,进行实验,相比传统的固定能量成像方式,CT信息完整,质量高.从而说明论文所提出的方法,能够实现CT系统动态范围的扩展,实现复杂结构件的高动态CT成像.For complicated structural components with wider X-ray attenuation ranges, the projection information is short of single-energy computed tomography （CT） imaging because the attenuation thickness of the components along the orientation of X-ray penetration exceeds the limit of the dynamic range of the CT imaging system. Then under this circumstance, in the conventional imaging mode of fixed ray energy the phenomenon of overexposure and underexposure easily occurs. The whole structure information cannot be obtained, and the projection information is seriously lacking, hence it will affect the quality of CT reconstruction. This paper proposes a CT imaging method with varying energy based on logarithm demodulation. 〈br〉 For the incomplete projection due to the limited dynamic range, we collect images at various rotation angles, as in standard CT; also, at each angle we collect a series of images at different energies and fuse them into a single high dynamic range （HDR） image. Based on this HDR image, the conventional CT reconstruction methods can get the full construction information. However, the CT quality is poor, because of noise amplification in the fusion process of X-ray image sequences which are gathered during varying the X-ray energy. To solve this problem, this paper proposes to use logarithm transformation to reduce the dynamic range for the varying energy image sequences. This can change the weight coe？cients’ access in the projection sequences to suppress the noise. Also in the transformation sequences, we can also use the fusion method, which is based on image gray consistency, to compute the weighting coe？cient, to obtain the HDR projection, because the logarithm transformation does not change the image structure, and the overlap area between image sequences is definite. Finally we use the conventional CT reconstruction algorithm to make the CT imaging with the complicated structural components. 〈br〉 An accompanying experiment with a complicated instrument demonstrates that the n

关 键 词：X射线能量 高动态CT 复杂结构件 对数解调 

分 类 号：TP391.41[自动化与计算机技术—计算机应用技术]