High Accuracy X-Ray Dual-Energy Experiments and Non-Rotational Tomography Algorithm for Explosives Detection Technique in Luggage Control Mihai Iovea 1 , Marian Neagu 1 , Octavian G. Duliu 2 , Gabriela Mateiasi 3 1 Accent Pro 2000, Ltd (www.accent.ro ), 1 Nerva Traian Str., K6, 031041 Bucharest, Romania, phone: +4074 518 2660, e-mail: office@accent.ro 2 University of Bucharest, Department of Atomic and Nuclear Physics, P.O. Box MG-11, 077125 Bucharest, Romania, e-mail: duliu@b.astral.ro 3 The Politehnica University, Bucharest, 313, Splaiul Independentei, 060032, Bucharest, Romania, e-mail: miovea@pcnet.ro Abstract The experiments using our laboratory dual-energy X-Ray Radioscopy/Tomography equipment reveals an accuracy better than 2% in measuring Z effective and around 5% in the weight measurement. In “dual- energy” X-ray tomography (CT) accuracy better than 3% in measuring Z effective and Density of scanned objects and less than 2% accuracy in materials identification (using also the attenuation coefficients comparison) has been obtained. Due too the high accuracy of both methods is it feasible to discriminate between water (or other typical standard organic materials found in baggage) and the liquid explosives. Also, by applying both methods successively, a much lower false positive alarm rate could be reached. Both techniques have been successfully checked using simulated explosives samples (manufactured by X- ray NESTT Co.- USA) having known values of Z effective and Density. Further, we present the simulated encouraging results of a new iterative reconstruction algorithm intended for replacing the actual rotational-based CT scanning method with a linear movement scan. The new algorithm is a combination of a classical ART with a fast ray-tracing algorithm for evaluation of rays’ pixels contribution. The main goal of the algorithm is to develop a new X-Ray CT machine for luggage control within the size and the cost of the actual standard X-Ray screening devices. Keywords: Dual-energy, CT, radioscopy, Effective Atomic number, luggage, screening, explosive detection 1. Introduction The X-ray Digital Radiography (DR) and Computed Tomography (CT) domains destined for luggage threats detections has been substantially developed within the last years due to the increase of the security measures after the events from 9/11 and after the series of terrorist attacks in Europe. The equipments have become more faster, offering a better resolution images, are now largely using the dual-energy technique for identifying the main class of materials (organic, non-organic and metallic) but only a few of the manufacturers have been approached directly the matter of accurate identification of the materials. Many of equipments are using a “simplified” dual-energy method for presenting coloured images of the scanned objects, the all organic substances being represented with a distinctive colour and the final decision still is Fig. 1 – The X-Ray dual-energy Radioscopy and Tomography laboratory equipment DIR 2007 - International Symposium on Digital industrial Radiology and Computed Tomography, June 25-27, 2007, Lyon, France