Speaker
Description
X-ray security screening is essential in high-security facilities such as airports and harbors. It can detect prohibited items and hazardous materials concealed in baggage. This screening process is critical to ensuring public safety. It enables the early detection and interception of dangerous items. Screening images taken with standardized test kits are commonly used to evaluate the performance of X-ray security scanners [1].
The Ministry of Land, Infrastructure, and Transport issues guidelines for the performance evaluation of X-ray security scanners in the Republic of Korea [2]. The TSA (Transportation Security Administration) ASTM test kit and the ECAC (European Civil Aviation Conference) STP test piece are used following these guidelines. Key evaluation metrics include ‘Wire Display’ and ‘Spatial Resolution’. Performance is evaluated under the standard operating conditions as specified by the equipment manufacturer.
In this study, the performance of a newly developed X-ray security scanner in terms of wire display and spatial resolution was experimentally evaluated using the ASTM F792-HP test kit (Fig. 1). These results were then compared and analyzed with the simulation results obtained by using a Geant4-based simulation model. The wire display evaluates the scanner's ability to detect sinusoidal wires placed in the test kit (Test 1). The quantitative criteria, as required by the Ministry’s guidelines, is based on the detection of wires as small as 30 AWG (0.254 mm). The test kit contains wires of different diameters (24, 30, 34, 38, and 42 AWG), allowing a comprehensive performance evaluation. A statistical algorithm was used to quantify wire display performance to increase objectivity and accuracy [3]. Both the experimental results and the simulation model confirmed that the scanner could detect wires of up to 34 AWG (0.160 mm).
Spatial resolution (Test 3 of the ASTM test kit) refers to the ability to distinguish between adjacent objects in the security screening image. The phantom consists of four bar patterns, each consisting of four bars of identical thickness, ranging from 0.5 mm to 2.0 mm (0.5, 1.0, 1.5, and 2.0 mm). The spacing between the bars in each pattern is equal to the bar thickness; for example, the 0.5 mm pattern has four bars, each 0.5 mm wide, spaced 0.5 mm apart. Spatial resolution performance is defined as the smallest distinguishable bar pattern that can be resolved in the security image [4]. Both experimental and simulation results confirmed that the scanner was able to resolve the 1.0 mm pattern, but not the 0.5 mm pattern. A refined phantom was implemented by the Geant4 model to further investigate the spatial resolution limit. Analysis of the refined phantom resulted in a final spatial resolution assessment of 0.8 mm, with a clear separation of the four peaks at 0.8 mm and no clear separation at 0.7 mm.
The results showed that the developed scanner met the domestic performance requirements. The simulation model accurately reflected the performance of the system. These results validate the reliability of the simulation model and provide a basis for its application in future performance evaluation and system optimization processes.
[1] Y. A. Yoon et al., 2021. Improving imaging quality assessment of cabinet X-ray security systems, J. Korean Soc. Qual. Manage. 49(1), 47-60
[2] Ministry of Land, Infrastructure and Transport, 2010. Aviation Security Act. Republic of Korea
[3] J. L. Glover and L. T. Hudson, 2016. An objectively-analyzed method for measuring the useful penetration of x-ray imaging systems, Meas. Sci. Technol. 27(6), 065402
[4] J. L. Glover et al., 2018. Testing the image quality of cabinet x-ray systems for security screening: The revised ASTM F792 standard, J. Test. Eval. 46(4), 1468-1477
| Workshop topics | Applications |
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