Effective noise reduction algorithm for material decomposition in dual-energy X-ray inspection

Abstract Dual-energy X-ray inspection can provide material-decomposed transmission information of the imaged object enhancing observer’s inspection performance. The material decomposition algorithms have an inherent noise amplification problem due to the multiplication and division operations during dual-energy image processing, which often degrades the material decomposition performance. In this work, we propose an effective and reliable clustering algorithm to resolve the noise amplification problem. The proposed method utilizes a k-means cluster algorithm as a base method with Gaussian noise of the data considered. In addition, we added a probabilistic regularization that can effectively relieve the decision challenge of the initial number of clusters. We have applied the proposed denoising method to the prototype X-ray dual-energy inspection system with an empirical calibration method that we have previously proposed. The proposed algorithm showed substantial reduction of noise in the test container projections and accordingly improved the material decomposition accuracy. Moreover, we performed quantitative analysis of the empirical calibration method with and without the cluster-based noise reduction algorithm and also on the conventional calibration method for material decomposition. It showed that the empirical calibration method with the noise reduction algorithm is robust against the thickness variation of the target object. The results suggest that the proposed noise reduction algorithm with the empirical calibration method is a promising solution to dual-energy X-ray material decomposition for inspection.