Seeing past the hard stuff

      According to an announcement released late June, American Science & Engineering (AS&E) reports the success of its Z Backscatter Van (ZBV) with over 400 sales in 46 countries. Its use varies "from seizures of large quantities of drugs, to the...


      According to an announcement released late June, American Science & Engineering (AS&E) reports the success of its Z Backscatter Van (ZBV) with over 400 sales in 46 countries. Its use varies "from seizures of large quantities of drugs, to the detection of stowaways and bulk explosives in war zones."

   Placing such powerful contraband detection in a mobile unit has certainly deemed an advantageous tactic, for the company and law enforcement alike. Yet, its unusual name "Z Backscatter" stands out; at first glance its results seem to appear similar to X-ray images — perhaps not, take a second look.

   Massachusetts-based AS&E was founded over 50 years ago by physicists from MIT. They originally formed the company to basically do a variety of research related activities primarily for the U.S. government in X-ray physics, science and technology, as stated by Joe Reiss, vice president of marketing at AS&E.

   The company, initially ran as a research and development outfit, developed X-ray telescopes to aid in imaging the universe, CT scans for medical imaging as well as X-rays for security applications. From there, focus turned toward homeland security and the war on drugs — more specifically narcotic smuggling.

   Looking to learn from history lest we repeat ourselves, AS&E was inspired from terrorist-like events of the past. For example, about three years ago the U.K. police uncovered liquid explosives — difficult to detect with X-ray.

   Backscatter imaging, as compared to X-ray, transpires when X-rays bounce off of the scanned objects. Reiss explains: "[X-rays] could give you an image through things that visible light won't go through. Scientists have known for a long time that not only will X-rays go through objects but will scatter off objects as well." Putting the concept into use, ZBV sends out X-rays toward the target, the resulting "scattered" radiation is then translated into such black-and-white-type images viewed within this article.

   To understand the contrast, in a typical "transmission" X-ray image, the higher density items appear while lower density objects print nearly translucent. "These transmission X-rays are great at locating heavy objects like guns or knives in bags, but then a new threat came along and that threat was explosive materials," he says.

   The mass of the atom or atomic number of the material, closely associated to the conventional term "density," dictates how X-rays react with that material. "The reason why that's interesting is it turns out there are a lot of other things that are made up of 'lighter' atoms that law enforcement cares about — it could be explosive materials, narcotics, currency or a stowaway," he adds. Basically, these items are typically made of organic compounds which tend to scatter X-rays more.

   While AS&E provides systems that utilize both transmission imaging and backscatter imaging, the ZBV only uses backscatter imaging in an effort to optimize detection.

   Representing this optimization, the Associated Press reported that using a ZBV, Border Patrol agents discovered 1,500 pounds of hidden marijuana and five illegal immigrants in a hidden compartment of a large truck. In this example the marijuana appeared in the image a bright white-ish color due to its lower density qualities. (This example is not represented in the images included with this article.)

   Presenting the technology's capabilities further, AS&E scanned one pallet of computer monitors with transmission X-ray and backscatter imaging at the same time to best display how the two display different pieces of the puzzle. One trick — they purposely placed bags of narcotic simulant around and in the monitors.

   Transmission X-ray images displayed each monitor clearly; monitors were outlined, each metal component a very obvious image letting any analyst understand what objects were inside.

   The backscatter results, however, illuminated the bags of narcotic simulant making any analyst aware of any organic-like material within.

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