Segmentation of suspicious objects in an x-ray image using automated region filling approach

Kenneth Fu; Clark Guest; Pankaj Das

doi:10.1117/12.826338

4 September 2009 Segmentation of suspicious objects in an x-ray image using automated region filling approach

Kenneth Fu, Clark Guest, Pankaj Das

Proceedings Volume 7445, Signal and Data Processing of Small Targets 2009; 744510 (2009) https://doi.org/10.1117/12.826338
Event: SPIE Optical Engineering + Applications, 2009, San Diego, California, United States

Abstract

To accommodate the flow of commerce, cargo inspection systems require a high probability of detection and low false alarm rate while still maintaining a minimum scan speed. Since objects of interest (high atomic-number metals) will often be heavily shielded to avoid detection, any detection algorithm must be able to identify such objects despite the shielding. Since pixels of a shielded object have a greater opacity than the shielding, we use a clustering method to classify objects in the image by pixel intensity levels. We then look within each intensity level region for sub-clusters of pixels with greater opacity than the surrounding region. A region containing an object has an enclosed-contour region (a hole) inside of it. We apply a region filling technique to fill in the hole, which represents a shielded object of potential interest. One method for region filling is seed-growing, which puts a "seed" starting point in the hole area and uses a selected structural element to fill out that region. However, automatic seed point selection is a hard problem; it requires additional information to decide if a pixel is within an enclosed region. Here, we propose a simple, robust method for region filling that avoids the problem of seed point selection. In our approach, we calculate the gradient Gx and Gy at each pixel in a binary image, and fill in 1s between a pair of x₁ _Gx(x1,y)=-1 and x₂ _Gx(x2,y)=1, and do the same thing in y-direction. The intersection of the two results will be filled region. We give a detailed discussion of our algorithm, discuss the strengths this method has over other methods, and show results of using our method.

Citation Download Citation

Kenneth Fu, Clark Guest, and Pankaj Das "Segmentation of suspicious objects in an x-ray image using automated region filling approach", Proc. SPIE 7445, Signal and Data Processing of Small Targets 2009, 744510 (4 September 2009); https://doi.org/10.1117/12.826338

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