FREE FDA REPORT: The FDA encourages manufactures and clinical uses to minimize the radiation exposure to patient and users. The free report is provided as educational material to you. Imaging exams should be conducted only when medically justified. When such exams are conducted, patients should be exposed to an optimal radiation dose – no more or less than what is necessary to produce a high-quality image.

This free informative pdf report,  great primer and overview as to how the backscatter x-ray imaging machine operates. Covers basic physics involved with backscatter imaging systems.  Just enter 0 for the price.