In image reconstruction for X-ray computed tomography, images reconstructed by filtered backprojection (FBP) include systematic errors because the FBP method does not take into account some of the properties of the ac...
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In image reconstruction for X-ray computed tomography, images reconstructed by filtered backprojection (FBP) include systematic errors because the FBP method does not take into account some of the properties of the actual imaging system such as the divergence of X-ray beam. One solution to this problem is to use algebraic reconstruction methods, such as generalized analytic reconstruction from discrete samples and natural pixel decomposition. However, in the process of reconstruction using these methods, it is necessary to solve the linear algebraic equations which have a large coefficient matrix. In this paper, we propose a method to accelerate the iteration solving these equations by preconditioning the coefficient matrix using a polynomial function. The results of the computer simulations show the effectiveness of the proposed method.
The single photon emission computed tomography (SPECT) imaging system has shift-variant characteristics due to non-uniform attenuation of gamma-ray, collimator design, scattered photons, etc. In order to provide quant...
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The single photon emission computed tomography (SPECT) imaging system has shift-variant characteristics due to non-uniform attenuation of gamma-ray, collimator design, scattered photons, etc. In order to provide quantitatively accurate SPECT images, these characteristics should be compensated in the reconstruction. This paper presents a new method to correct the shift-variant characteristics, which is based on a continuous-discrete mapping model and filtered backprojection (FBP) method, in which the projection data are assumed to be acquired by narrow ray sum beams in the FBP method and the assumed data set is expressed as a linear combination of the actual projection data. Narrow ray sum beams are approximated by a weighted sum of the original sensitivity functions. Thus, at the reconstruction the projection data are first modified using an approximation and the FBP method is then applied to the corrected projection data and a SPECT image is reconstructed. We further propose a technique that requires the inversion of smaller matrices than the conventional algebraic method;the amount of calculation and memory space become smaller and the stability of the calculation is greatly improved as well. The results of the numerical simulations are also demonstrated.
SPECT imaging system has shift-variant characteristics due to nonuniform attenuation of gamma-ray, collimator design, scattered photons, etc. In order to provide quantitatively accurate SPECT images, these shift-varia...
详细信息
ISBN:
(纸本)0819424455
SPECT imaging system has shift-variant characteristics due to nonuniform attenuation of gamma-ray, collimator design, scattered photons, etc. In order to provide quantitatively accurate SPECT images, these shift-variant characteristics should be compensated in reconstruction. This paper presents a method to correct the shift-variant characteristics based on a continuous-discrete mapping model. In the proposed method, the projection data are modified using sensitivity functions so that Filtered Backprojection (FBP) method can be applied. Since the projection data are assumed to be acquired by narrow ray sum beams in the FBP method, narrow ray sum beams are approximated by a weighted sum of sensitivity functions of the measurement system, then the actual projection data are corrected by the weighting factors. Finally, FBP method is applied to the corrected projection data and a SPECT image is reconstructed. Since the proposed method requires the inversion of smaller matrices than the conventional algebraic methods, the amounts of calculation and memory space become smaller, and the stability of the calculation is greatly improved as well. The results of the numerical simulations are also demonstrated.
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