Easier X-ray detection of concealed drugs and explosives
- Published: Feb 19, 2013
- Author: Steve Down
- Channels: Chemometrics & Informatics / X-ray Spectrometry
Drugs and explosives hidden internally by body packers can be detected more easily by energy dispersive X-ray diffraction using novel feature extraction techniques developed by Chinese scientists. The full potential of EDXRD in this area has not been fully realised due to interference from the body packer's own body, limits on detection time and poor spectral quality, particularly low signal-to-noise ratios. As a result, the spectral peaks originating from the contraband are difficult to pinpoint.
The new approach by Jinhuai Liu from the Institute of Intelligent Machines, Hefei, and colleagues, has countered these problems by combining the use of a discrete cosine transform (DCT) and linear discriminant analysis (LDA), as reported in Analytical Methods. DCT provides an effective way to carry out dimension reduction in order to extract the features representing the drugs or explosives, while LDA extracts the features corresponding by class discrimination.
The procedure was demonstrated on an artificial body comprising head, chest and abdomen that simulated more than 20 organs. The test substances were placed in centrifuge tubes and inserted to a depth of 8 cm in the stomach to represent a body packer swallowing contraband. For the drugs methamphetamine and heroin, the drug precursors phenylacetic acid and piperonal, the explosive TNT and the disruptors flour and sodium chloride, the average recognition rate was improved to more than 97%.
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