My K1 visa was approved finally last week (yay)

and I fly out in a few weeks...my question is: one person at the embassy told me to put the chest x-ray in my checked luggage and another said to put it in my carry on....does anyone know which it is? And will taking it through an airport scanner damage it at all?
Also a really stupid question probably but is any US airport an approved point of entry? I'm flying Gatwick - Detroit and then connecting to my final US destination.
Thanks