State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing, P. R. China.
Department of Nuclear Science and Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, P. R. China.
J Xray Sci Technol. 2018;26(5):853-864. doi: 10.3233/XST-180396.
Development of spectral X-ray computer tomography (CT) equipped with photon counting detector has been recently attracting great research interest. This work aims to improve the quality of spectral X-ray CT image. Maximum a posteriori (MAP) expectation-maximization (EM) algorithm is applied for reconstructing image-based weighting spectral X-ray CT images. A spectral X-ray CT system based on the cadmium zinc telluride photon counting detector and a fat cylinder phantom were simulated. Comparing with the commonly used filtered back projection (FBP) method, the proposed method reduced noise in the final weighting images at 2, 4, 6 and 9 energy bins up to 85.2%, 87.5%, 86.7% and 85%, respectively. CNR improvement ranged from 6.53 to 7.77. Compared with the prior image constrained compressed sensing (PICCS) method, the proposed method could reduce noise in the final weighting images by 36.5%, 44.6%, 27.3% and 18% at 2, 4, 6 and 9 energy bins, respectively, and improve the contrast-to-noise ratio (CNR) by 1.17 to 1.81. The simulation study also showed that comparing with the FBP and PICCS algorithms, image-based weighting imaging using MAP-EM statistical algorithm yielded significant improvement of the CNR and reduced the noise of the final weighting image.
配备光子计数探测器的能谱 X 射线计算机断层扫描（CT）的发展最近引起了极大的研究兴趣。本工作旨在提高能谱 X 射线 CT 图像的质量。最大后验（MAP）期望最大化（EM）算法被应用于基于图像的加权能谱 X 射线 CT 图像的重建。基于碲化镉锌光子计数探测器的能谱 X 射线 CT 系统和脂肪圆柱体体模进行了模拟。与常用的滤波反投影（FBP）方法相比，该方法将最终加权图像中的噪声降低了 2、4、6 和 9 个能窗，分别为 85.2%、87.5%、86.7%和 85%。CNR 提高了 6.53 到 7.77。与基于先验图像约束的压缩感知（PICCS）方法相比，该方法在 2、4、6 和 9 个能窗处可将最终加权图像的噪声降低 36.5%、44.6%、27.3%和 18%，并将对比度噪声比（CNR）提高 1.17 到 1.81。模拟研究还表明，与 FBP 和 PICCS 算法相比，基于 MAP-EM 统计算法的基于图像的加权成像可显著提高 CNR 并降低最终加权图像的噪声。
