3D robust anisotropic diffusion filtering algorithm for sparse view neutron computed tomography 3D image reconstruction

The most critical part of a neutron computed tomography (NCT) system is the image processing algorithm, which directly affects the quality and speed of the reconstructed images. Various types of noise in the system can degrade the quality of the reconstructed images. Therefore, to improve the quality of the reconstructed images of NCT systems, efficient image processing algorithms must be used. The anisotropic diffusion filtering (ADF) algorithm can not only effectively suppress the noise in the projection data, but also preserve the image edge structure information by reducing the diffusion at the image edges. Therefore, we propose the application of the ADF algorithm for NCT image reconstruction. To compare the performance of different algorithms in NCT systems, we reconstructed images using the ordered subset simultaneous algebraic reconstruction technique (OS-SART) algorithm with different regular terms as image processing algorithms. In the iterative reconstruction, we selected two image processing algorithms, the Total Variation and split Bregman solved total variation algorithms, for comparison with the performance of the ADF algorithm. Additionally, the filtered back-projection algorithm was used for comparison with an iterative algorithm. By reconstructing the projection data of the numerical and clock models, we compared and analyzed the effects of each algorithm applied in the NCT system. Based on the reconstruction results, OS-SART-ADF outperformed the other algorithms in terms of denoising, preserving the edge structure, and suppressing artifacts. For example, when the 3D Shepp–Logan was reconstructed at 25 views, the root mean square error of OS-SART-ADF was the smallest among the four iterative algorithms, at only 0.0292. The universal quality index, mean structural similarity, and correlation coefficient of the reconstructed image were the largest among all algorithms, with values of 0.9877, 0.9878, and 0.9887, respectively.