An X ray-cosmic ray combined dual-model reconstruction approach for vehicle/container inspection

Cosmic-ray tomography is an effective non- destructive technology which was originally developed to detect high-Z nuclear materials. Further research showed that after taking part in soft cosmic ray (such as electrons), this technology can discriminate medium- and low-Z materials, but presenting poor material resolution. In order to fight against smuggling and seizing hazardous goods, it’s significant to improve the material resolutionof medium- and low-Z materials. In this paper, we propose an X-ray & cosmic-raycombined dual-model reconstruction approach. X-ray system obtainstransparency, structure and height information of the inspected vehicle/container, then cosmic ray tomography system reconstructs image using both cosmic-ray and X-ray information, where thecargo transparency value helps to divide different Z regions, structure determines the location of stopping effect, andmaterial thickness improves the calculations of stopping power and scattering density. Geant4 simulation program and ROC (receiver operating characteristic) analysis are used to validate the proposed approach. Results show that in 1 minute’s inspection time, the dual-model reconstruction approach can achieve detection rate of above 65%, with AUC (the area under the ROC curve) value of higher than 0.75, much better than those of standalone cosmic-ray approach by 30% and 0.46. The dual- model reconstruction approach can effectively enhance the classification ability of medium- and low-Zmaterials.