6946

Four-dimensional Cone Beam CT Reconstruction and Enhancement using a Temporal Non-Local Means Method

Xun Jia, Zhen Tian, Yifei Lou, Jan-Jakob Sonke, Steve B. Jiang
Center for Advanced Radiotherapy Technologies and Department of Radiation Medicine and Applied Sciences, University of California San Diego, La Jolla, CA 92037, USA
arXiv:1201.2450v1 [physics.med-ph] (12 Jan 2012)

@article{2012arXiv1201.2450J,

   author={Jia}, X. and {Tian}, Z. and {Lou}, Y. and {Sonke}, J.-J. and {Jiang}, S.~B.},

   title={"{Four-dimensional Cone Beam CT Reconstruction and Enhancement using a Temporal Non-Local Means Method}"},

   journal={ArXiv e-prints},

   archivePrefix={"arXiv"},

   eprint={1201.2450},

   primaryClass={"physics.med-ph"},

   keywords={Physics – Medical Physics},

   year={2012},

   month={jan},

   adsurl={http://adsabs.harvard.edu/abs/2012arXiv1201.2450J},

   adsnote={Provided by the SAO/NASA Astrophysics Data System}

}

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Four-dimensional Cone Beam Computed Tomography (4D-CBCT) has been developed to provide respiratory phase resolved volumetric imaging in image guided radiation therapy (IGRT). Inadequate number of projections in each phase bin results in low quality 4D-CBCT images with obvious streaking artifacts. In this work, we propose two novel 4D-CBCT algorithms: an iterative reconstruction algorithm and an enhancement algorithm, utilizing a temporal nonlocal means (TNLM) method. We define a TNLM energy term for a given set of 4D-CBCT images. Minimization of this term favors those 4D-CBCT images such that any anatomical features at one spatial point at one phase can be found in a nearby spatial point at neighboring phases. 4D-CBCT reconstruction is achieved by minimizing a total energy containing a data fidelity term and the TNLM energy term. As for the image enhancement, 4D-CBCT images generated by the FDK algorithm are enhanced by minimizing the TNLM function while keeping the enhanced images close to the FDK results. A forward-backward splitting algorithm and a Gauss-Jacobi iteration method are employed to solve the problems. The algorithms are implemented on GPU to achieve a high computational efficiency. The reconstruction algorithm and the enhancement algorithm generate visually similar 4D-CBCT images, both better than the FDK results. Quantitative evaluations indicate that, compared with the FDK results, our reconstruction method improves contrast-to-noise-ratio (CNR) by a factor of 2.56~3.13 and our enhancement method increases the CNR by 2.75~3.33 times. The enhancement method also removes over 80% of the streak artifacts from the FDK results. The total computation time is ~460 sec for the reconstruction algorithm and ~610 sec for the enhancement algorithm on an NVIDIA Tesla C1060 GPU card.
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