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BAXSTER
Image quality tester for X-ray baggage screening systems
X-ray baggage screening systems at airports are a powerful tool to maintain aviation safety and to prevent or avoid terrorist acts. These systems produce an image of a baggage item that has to be judged by a human operator. It is of great importance that X-ray systems perform optimally, and are regularly tested. Therefore, there is a need for an objective and easy test method to measure the image quality of X-ray baggage screening systems with the human-in-the-loop.
BAXSTER (BAggage X-ray Screening TEsteR) is a new image quality tester for X-ray baggage screening systems. The purpose of the test apparatus is to standardize X-ray image performance measurement and to increase the reliability of baggage screening at airports. TNO Human Factors developed a prototype of BAXSTER for the US Transportation Security Administration (TSA, former FAA). With BAXSTER, the image quality of X-ray baggage screening systems can be tested easily and objectively.
Basically, the test apparatus consists of a set of test charts and a laptop computer that controls the tests and analyses the results. The charts contain triangular test patterns of various metals of different size and thickness. These charts are scanned by the X-ray system like a regular baggage item. The operator has to judge the orientation of these patterns on the X-ray image and uses a joystick to transfer his choices to the computer. The results of the test indicate the performance (relating to detection, resolution and penetration through metal) for the entire system, including the display, the operator and the effect of environmental conditions. The effectiveness of automatic object detection and material discrimination through dual-energy X-ray analysis cannot be tested with the current version of BAXSTER.
Features
BAXSTER is very easy to use: it is comparable to an eye chart test but applied now for evaluating of a complete X-ray system. The test is based on the patented TOD method, developed by TNO. The results have a direct relationship with object recognition. Unlike existing tests, the BAXSTER test requires no specific training and yields image quality measures that are independent from subjective judgements by the observer. The consistency of the results is analysed statistically. No electronic connection with the X-ray system is required. Finally, the test is fully computer controlled.
Applications
 The system can be used for support by the procurement of baggage screening systems for airport security, comparison of competing X-ray systems, delivery tests and routine tests. Another application is the evaluation of medical X-ray diagnostic systems.
A typical X-ray image in a BAXSTER test: the observer is instructed by the laptop to judge the orientation of a series of triangular test patterns: the orientation can be Up, Down, Right or Left.
TNO Human Factors develops knowledge focussed on human behaviour and performance in a demanding environment. We apply this knowledge to the innovation of processes, products and services for the Netherlands’ Armed Forces, private enterprises and governments.
TNO Human Factors
P.O.Box 23
3769 ZG Soesterberg
The Netherlands
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Web: www.tm.tno.nl
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