Originally Posted by sbagdon
These devices operate on a physical process called backscatter. Backscatter uses X-rays that reflect away ("scatter back") from the low-Z material (skin, clothing) but not most high-Z material (metal). Backscatter then makes "reflections" that define the high-Z materials as separate and distinct images from low Z.
Isn't that a little too much radiation exposure to be used routinely on everyone?