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KMID : 1137820150360050211
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의공학회지
2015 Volume.36 No. 5 p.211 ~ p.220
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Penalized-Likelihood Image Reconstruction for Transmission Tomography Using Spline Regularizers
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Jeong J.-E.
Lee Soo-Jin
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Abstract
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Recently, model-based iterative reconstruction (MBIR) has played an important role in transmission tomography by significantly improving the quality of reconstructed images for low-dose scans. MBIR is based on the penalized-likelihood (PL) approach, where the penalty term (also known as the regularizer) stabilizes the unstable likelihood term, thereby suppressing the noise. In this work we further improve MBIR by using a more expressive regularizer which can restore the underlying image more accurately. Here we used a spline regularizer derived from a linear combination of the two-dimensional splines with first- and second-order spatial derivatives and applied it to a non-quadratic convex penalty function. To derive a PL algorithm with the spline regularizer, we used a separable paraboloidal surrogates algorithm for convex optimization. The experimental results demonstrate that our regularization method improves reconstruction accuracy in terms of both regional percentage error and contrast recovery coefficient by restoring smooth edges as well as sharp edges more accurately.
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KEYWORD
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transmission tomography, image reconstruction, iterative method, penalized likelihood, regularization, spline, convex optimization
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