I suggest you just tell the TSA exactly what your situation is. If you don't want to say it out loud, write it down on a piece of paper ahead of time and hand it to the person who asks you to go through the scanner. Then, if there is any anomaly on the scanner, they know what it is. This doesn't guarantee that you won't get a pat down, but it may help. Given the bad publicity the TSA has gotten recently, I have noticed that they often do not scan or pat down kids, the elderly or disabled.