A method for simultaneous correction of spectrum hardening artifacts in CT images containing both bone and iodine
A method for simultaneous correction of spectrum hardening artifacts in CT images containing both bone and iodine
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DOI：
10.1118/1.597970
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发表时间：
1997-10-01
期刊：
影响因子：
3.8
通讯作者：
Ruth, C
中科院分区：
文献类型：
--
作者：
Joseph, PM;Ruth, C
描述了一种能够校正由于任意数量的物质中的射束硬化而导致的X射线计算机断层扫描（CT）图像中的伪影的方法。该方法与重建的图像数据一起工作，并且不需要原始的原始数据。有必要对入射X射线束的光谱进行估计。该方法类似于先前描述的校正由骨骼引起的伪影的迭代方法。我们的实施旨在纠正骨骼和碘造影剂的硬化。有必要识别图像中包含骨和碘的那些区域。一个中心概念是有效密度，即物质的CT数与水的CT数之比。有必要通过初步实验建立CT数与碘或骨的质量密度之间的关系。根据这些数据，使用应用于给定图像的重投影算法来估计通过软组织（水当量）、骨和碘的路径积分。给定该输入，数值地求解关键方程，其提供要从重新投影的数据中减去的校正项。假设原始密度估计是正确的，这可以证明消除了由于射束硬化而引起的投影中的非线性项。原则上，可以迭代地重复该方法以提高精度。然而，在我们使用Siemens Evolution电子束断层扫描仪扫描的含有碘酞酸葡胺和K2HPO4的体模图像的经验中，校正图像的质量非常好，研究的体模不需要进一步迭代。需要更多的研究来实现临床扫描的方法。(C)1997年美国医学物理学家协会。
A method is described capable of correcting artifacts in x-ray computer tomography (CT) images due to beam hardening in an arbitrary number of substances. The method works with reconstructed image data and does not require the original raw data. It is necessary to have an estimate of the spectrum of the incident x-ray beam. The method is similar to previously described iterative methods that correct artifacts induced by bones. Our implementation was designed to correct for hardening in both bone and iodine contrast agent. It is necessary to identify those regions of the image which contain bone and iodine. A central concept is that of effective density, which is the ratio of CT number of the substance to that of water. It is necessary to establish by a preliminary experiment the relationship between CT number and mass density of iodine or bone. From these data one estimates path integrals through soft tissue (water equivalent), bone, and iodine using a reprojection algorithm applied to the given image. Given this input, a key equation is solved numerically which provides a correction term to be subtracted from the reprojected data. This can be shown to eliminate the nonlinear terms in the projections due to beam hardening, assuming that the original density estimates were correct. In principle, the method can be repeated iteratively to improve the accuracy. However, in our experience using an image of a phantom containing iothalamate meglumine and K2HPO4, scanned using the Siemens Evolution electron beam tomography scanner, the quality of the corrected image was excellent and no further iteration is needed for the phantoms studied. More research is needed to implement the method on clinical scans. (C) 1997 American Association of Physicists in Medicine.