ALERT | Awareness and Localization of Explosive-Related Threats

Toward Model-Based Reconstruction in Scanned Baggage Security Applications
F3-A5

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While traditional direct reconstruction algorithms such as filtered back projection de­pend on the analytic inversion of sinogram data, model-based reconstruction methods are based on the iterative optimization of a statistical model of both the acquired data and the unknown image.
Model-based reconstruction offers many important potential advantages over traditional methods of direct reconstruction for the security screening of checked baggage. It has the potential to reduce metal artifacts, improve resolution, reduce artifacts such as cupping that can systematically distort CT number estimates, incorporate tighter integration of reconstruction and segmentation, and sup­port reconstruction from scanners with a small number of projections. All these enhancements have the potential to improve the Pd/Pfa tradeoff for CT security screening systems.

The objective of this research is to investigate and quantify the value of model-based reconstruction for baggage security screening. To do this, our first goal is to implement a general model-based re­construction algorithm for use on multi-slice helical scan CT scanners and to test and evaluate this algorithm on scans of luggage provided by the ALERT Center. In addition, we will have an ongoing goal of identifying and investigating opportunities for adapting and improving the model-based recon­struction technology for use in security applications. In particular, we will study the use of advanced forward and prior models for reducing metal artifacts, improving segmentation accuracy, and im­proving CT number estimation.