摘要
X射线工业CT中,由于X射线能谱具有多色性,X射线在透射物质时,能量较低的射线优先被吸收,X射线能量越高,衰减系数越低。也即较高能量的X射线的衰减系数比较低能量的X射线的衰减系数小。射线随透射厚度增大,变得更易穿透,也就是发生了能谱硬化现象。由于射线硬化现象使图像重建时出现伪影,因此必须修正。文中对X射线硬化现象进行了分析,探讨了在均匀物质中,X射线射束和与透射厚度的关系。并根据Beer定律和X射线与物质作用的特点,通过获取X射线射束和数据,拟合出射束和与透射厚度的关系式。然后得出在同一透射厚度时,X射线射束和校正为单色等效射束和的关系及其等效方法。最终得出X射线等效单色射线的衰减系数的拟合值。再对此衰减系数拟合值进行卷积反投影重构,即可有效消除X射线射束硬化的影响。
Since energy spectrum of X-ray is polychromatic source in attenuation coefficient with energy leads to the lower energy of X-ray X-ray industrial computerized tomography, the variation of radiation being absorbed preferentially when X-ray is transmitting the materials. And the higher the energy of X-ray, the lower the attenuation coefficient of X-ray. With the increase in the X-ray transmission thickness, it becomes easier for the X-ray to transmit the matter. Thus, the phenomenon of energy spectrum hardening of X-ray takes place, resulting from the interaction between X-ray and the materials. This results in false images in the reconstruction of X-ray industrial computerized tomography. Therefore, hardening correction of energy spectrum of X-ray has to be done. In the present paper, not only is the hardening phenomenon of X-ray transmitting the materials analyzed, but also the relation between the X-ray beam sum and the transmission thickness of X-ray is discussed. And according to the Beer law and the characteristics of interaction when X-ray is transmitting material, and by getting the data of X-ray beam sum, the relation equation is fitted between the X-ray beam sum and X-ray transmission thickness. Then, the relation and the method of equivalence are carried out for X-ray beam sum being corrected. fitted value for X-ray transmitting the material is reasoned out. Finally, the equivalent and monochromatic attenuation coefficient The attenuation coefficient fitted value is used for product back- projection image reconstruction in X-ray industrial computerized tomography. Thus, the effect caused by X-ray beam hardening is wiped off effectively in X-ray industrial computerized tomography.
出处
《光谱学与光谱分析》
SCIE
EI
CAS
CSCD
北大核心
2008年第6期1426-1429,共4页
Spectroscopy and Spectral Analysis
基金
国家科委“八五”火炬计划项目
湖南省自然科学基金项目(07JJ6106)
湖南“十一五”重点建设-学科光学基金项目
湖南省教育厅科研项目(06C606)资助
关键词
X射线
ICT
硬化校正
射束和
X-ray
Industrial computerized tomography
Hardening correction
Beam sum