When Z Backscatter and transmission X-ray technologies are combined, the result is the most effective and comprehensive detection system available anywhere. While Z Backscatter excels in the detection of organics, the addition of transmission X-ray capability enhances detection capability and the ability to penetrate dense materials and complex environments.

Transmission X-ray images result when these X-rays pass through an object, and are absorbed rather than scattered. When viewed on a transmission monitor, these X-rays create a "shadowgram" image, similar to the result of a medical X-ray exam. "Shadowgram" images are generally high resolution, and result from the X-ray beam being absorbed by objects of varying densities.

Dual-energy transmission technology uses two X-ray energy levels to determine the atomic number of objects in the parcel and then colorizes the image based on material type - organic materials are orange, mixed materials are green, and metallics are blue.

While transmission technology can reveal fine details such as wires and other bomb components, and sometimes discriminate between materials, the more objects or clutter in the path of the beam, the less object and material differentiation is achieved. To limit its significant shortcomings, transmission X-rays should only be implemented in combination with Z Backscatter technology. Viewing both images simultaneously gives inspectors richly detailed information about the contents of a parcel or container. Z Backscatter technology highlights organic materials, such as explosives and narcotics - materials that traditional transmission-only systems can miss. Z Backscatter's photo-like images also complement transmission X-rays by providing context and clarity to expedite inspections.

This diagram shows the basic principle of AS&E's Z Backscatter and transmission imaging systems.