The x-ray spectrum recorded by a photon-counting x-ray detector (PCXD) is distorted due to the following physical
effects which are independent of the count rate: finite
energy-resolution, Compton scattering, charge-sharing, and Kescape.
If left uncompensated, the spectral response (SR) of a PCXD due to the above effects will result in image
artifacts and inaccurate material decomposition. We propose a new SR compensation (SRC) algorithm using the
sinogram restoration approach. The two main contributions of our proposed algorithm are: (1) our algorithm uses an
efficient conjugate gradient method in which the first and second derivatives of the cost functions are directly calculated
analytically, whereas a slower optimization method that requires numerous function evaluations was used in other work;
(2) our algorithm guarantees convergence by combining the non-linear conjugate gradient method with line searches that
satisfy Wolfe conditions, whereas the algorithm in other work is not backed by theorems from optimization theory to
guarantee convergence. In this study, we validate the performance of the proposed algorithm using computer
simulations. The bias was reduced to zero from 11%, and image artifacts were removed from the reconstructed images.
Quantitative K-edge imaging in possible only when SR compensation is done.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Somesh Srivastava ; Jochen Cammin ; George S. K. Fung ; Benjamin M. W. Tsui and Katsuyuki Taguchi
"Spectral response compensation for photon-counting clinical x-ray CT using sinogram restoration", Proc. SPIE 8313, Medical Imaging 2012: Physics of Medical Imaging, 831311 (February 23, 2012); doi:10.1117/12.911394; http://dx.doi.org/10.1117/12.911394