Originally Posted by
cardiomd
If it would see full cavity it would likely need to be transmission Xray, not backscatter. These are used in prisons and customs but need even higher doses.
The only difference between transmission Xray and backscatter Xray is the wavelength of electromagnetic radiation being emitted.
My theory is that the TSA's backscatter machines can be adjusted to emit transmission Xrays, which would permit full body cavity searches, and that is why TSA prefers backscatter machines over MMW machines.