always ask, do you really need this test? and if you do, is there a different test without the radiation, an mri, an ultrasound, which would provide the same information? and is the machine set to a child's dose? and there is good news. little lucas, his arm was not broken, but he did need that low-dose radiation to confirm it. dr. richard besser, abc news, new york. >> so weird. and it's hard for doctors to tell how much radiation a child is getting because it varies by age and also by the brand of the machine. >> that's right. but i think what's good is under the fda's proposed guidelines, manufacturers of these devices have to provide that specific information on how to minimize radiation exposures for children of different sizes, different ages. radiation for a 6-year-old is very different, i think, radiation for a 12-year-old. >> if there's a button that says child dose, hit that one for the little one. >> hit that one instead. "the skinny," lots of good stuff coming up today. we'll be right back. >> announcer: abc's "world news