Dual energy computed tomography (DECT) can provide the information of the attenuation coefficient function of the scanned object. The classic projection-domain decomposition methods have been proposed to achieve this goal in which two components to delineate the attenuation coefficient function are used to decompose the projection data. In medical applications, the scanned body is typically composed of many types of materials, such as bone, soft tissue, fat and blood. Thus the attenuation coefficient function can be naturally decomposed with three or more components. However, as the number of the components is more than two, the two projection datasets of DECT are theoretically insufficient to perform the decomposition. Some works have proposed the multi-materials decomposition method using DECT in which each pixel of scanned object was decomposed with a group of three basis materials picked from a material library. However, this method requires a projection-domain decomposition firstly to estimate the attenuation coefficient function of the scanned object. The problem of the projection-domain method is that the spectrum of the x-ray source or additional calibration data is necessary. However, these two requirements may not be satisfied in practice. To address this issue, we propose an image-domain multi-materials decomposition method using DECT. Specifically, the dual energy images are jointly denoised by guided filtering with separable quadratic surrogate and then we calculate the adaptive attenuation function from the reconstruction images to perform the multi-materials decomposition.
1) Low-energy and 2) High-energy reconstructed images of the clinical DECT data
The multi-materials decomposed images
T. Zhao, K. Kim, D. Wu, Q Li, Multi-Materials Decomposition using clinical Dual-energy CT, IEEE Nuclear Science Symposium and Medical Imaging Conference (NSSMIC), Oct. 2017.