Affiliations: [a] Jiangxi Key Laboratory of Numerical Simulation Technology, School of Mathematics and Computer Science, Gannan Normal University, Ganzhou, China
| [b] Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| [c] School of Science, Hangzhou Dianzi University, Hangzhou, China
Correspondence:
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Corresponding author: Jing Wang, Ph.D., Division of Medical Physics and Engineering, Department of Radiation
Oncology, The University of Texas Southwestern Medical Center, 2280 In wood Rd., Dallas, TX 75235-9303. Tel.: +1
214 648 1795 (office); E-mail: jing.wang@utsouthwestern.edu.
Abstract: BACKGROUND:Triple-energy computed tomography (TECT) can obtain x-ray attenuation measurements at three energy spectra, thereby allowing identification of different material compositions with same or very similar attenuation coefficients. This ability is known as material decomposition, which can decompose TECT images into different basis material image. However, the basis material image would be severely degraded when material decomposition is directly performed on the noisy TECT measurements using a matrix inversion method. OBJECTIVE:To achieve high quality basis material image, we present a statistical image-based material decomposition method for TECT, which uses the penalized weighted least-squares (PWLS) criteria with total variation (TV) regularization (PWLS-TV). METHODS:The weighted least-squares term involves the noise statistical properties of the material decomposition process, and the TV regularization penalizes differences between local neighboring pixels in a decomposed image, thereby contributing to improving the quality of the basis material image. Subsequently, an alternating optimization method is used to minimize the objective function. RESULTS:The performance of PWLS-TV is quantitatively evaluated using digital and mouse thorax phantoms. The experimental results show that PWLS-TV material decomposition method can greatly improve the quality of decomposed basis material image compared to the quality of images obtained using the competing methods in terms of suppressing noise and preserving edge and fine structure details. CONCLUSIONS:The PWLS-TV method can simultaneously perform noise reduction and material decomposition in one iterative step, and it results in a considerable improvement of basis material image quality.
Keywords: Triple-energy CT, image-based material decomposition, penalized weighted
least-squares, total variation
