I am not a scientist but I don't think there is a machine that can detect alcohol with an XRay. I think they look for bottle shapes or do random searches. If there is such a machine I don't think RCCl would invest in them just to cut down on alcohol brought aboard.
I saw last week many people going to their rooms to fill up their RCCL mugs all week. I even saw a girl with a full bottle of tequila on the sun deck. One of the bar waiters told her she could not have that upstairs and she needed to take it down to her room. They did not take it from her. I do not bring booze but I do bring wine for dinner. I can understand people doing it though it does get expensive. The price for a mixed drink is $5.95 plus a 15% tip is $6.84 each. 25 drinks = $171. Minus $25 for the bottle is $146 in savings. That's alot of money to many people. I think if someone does this they need to throw some extra money to the bar tenders and waiters, I am not crying for the cuise line but would not like to see the staff get hurt, thats their living.