An improved ART algorithm for attenuation coefficient reconstruction of tomographic gamma scanners

A method of reconstructing the attenuation coefficient in the case of tomographic gamma scanning (TGS) imaging of nuclear waste tanks is proposed. The method was developed on the basis of the algebraic reconstruction technique (ART) method and is called the simultaneous iterative reconstruction techniques diagonally relaxed orthogonal projections (SIRT-DROP) method. To evaluate the accuracy of the method, a multi-layer model was designed. Each layer consisted of 25 (5 × 5) voxels, and each pixel measured 12 ×12× 12 cm. Results indicated that a maximum uncertainty of 34.88% and an average uncertainty of 14% were obtained when applying the ART method, while a maximum uncertainty of 16.11% and an average uncertainty of 9.96% were obtained when applying the proposed SIRT-DROP method. By performing linear regression in a C-language program on the energy–mass attenuation coefficient, the maximum and average uncertainties of the energy–mass attenuation coefficient were 35.32% and 15.67%, respectively, when the ART method was applied. When the SIRT-DROP method was applied, the maximum and average uncertainties of the energy–mass attenuation coefficient were lowered to 22.43% and 8.01%, respectively. Monte Carlo simulation results verified the capability of the proposed method, and the reconstructed attenuation coefficient was in an agreement with the pre-set value.