I am not sure how things work at your airport, but you may be able to pick a line without the option of an image scanner. Denver usually filters into about 6-8 lines for security and you can see in advance that at least 2 will only have a metal detector. They're generally the faster lines, too, so it doesn't look suspicious to pick them

In better news, I just made it through my first image scanner in Omaha that I wasn't singled out for a patdown afterwards. Maybe as my back gets stronger, the metal becomes less visible! (Note to self - don't skip pilates tomorrow...)