TY - GEN
T1 - Spectral response compensation for photon-counting clinical x-ray CT using sinogram restoration
AU - Srivastava, Somesh
AU - Cammin, Jochen
AU - Fung, George S.K.
AU - Tsui, Benjamin M.W.
AU - Taguchi, Katsuyuki
PY - 2012
Y1 - 2012
N2 - 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.
AB - 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.
KW - Photon-counting detectors
KW - clinical x-ray CT
KW - conjugate gradient
KW - convergent algorithms
KW - image reconstruction
KW - maximum likelihood estimation
KW - optimization methods
KW - sinogram restoration
UR - http://www.scopus.com/inward/record.url?scp=84860356080&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84860356080&partnerID=8YFLogxK
U2 - 10.1117/12.911394
DO - 10.1117/12.911394
M3 - Conference contribution
AN - SCOPUS:84860356080
SN - 9780819489623
T3 - Progress in Biomedical Optics and Imaging - Proceedings of SPIE
BT - Medical Imaging 2012
T2 - Medical Imaging 2012: Physics of Medical Imaging
Y2 - 5 February 2012 through 8 February 2012
ER -