Restoration of Missing Data in Limited Angle Tomography Based on Consistency Conditions
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چکیده
In limited angle tomography, only a limited angular range of data is acquired and consequently a double wedgeshaped region in the frequency domain representation of the imaged object is missing. Hence, streak artifacts occur. To restore the missing data, we perform a regression and an image fusion in sinogram domain and frequency domain, respectively. We first convert the sinogram restoration problem into a regression problem based on the Helgason-Ludwig consistency conditions. Due to the severe ill-posedness of the problem, regression only partially recovers the correct frequency components, especially lower frequency components, and will introduce erroneous ones, particularly higher frequencies. Bilateral filtering is utilized to retain the most prominent high frequency components and suppress erroneous ones. A fusion of the filtered image and the image reconstructed from the limited angle sinogram is performed afterwards in the frequency domain. The proposed method is evaluated on the Shepp-Logan phantom, for which the root-mean-square error of the reconstructed image decreases from 310 HU to 136 HU.
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تاریخ انتشار 2017