There is no safe dose of radiation
Whilst I don't want to knock security, I would just point out that anyone who says that radiation risk is a function of exposure is technically wrong. Whilst the probability of cellular changes (and malignancies) certainly increases with exposure (exposure = dose x time), radiation is unique amongst toxic agents insofar that there is no virtual safe dose. It just takes one photon / particle to hit a gene that may result in a mutation.
Yes, the dose will be small and the probability low, but it's still Russian roulette albeit with one shot in an unknow number of barrels.
Bottom line: I'll opt for the pat down every time.
Will