Hi Chris... You are right, about bone scans being done, before the age of three, Samantha had one done at dx, at age two, and then another, just recently at age 6... they would have done them more frequently, (Like one a year) but with the type of cancer she had, they know these kids are more prone to radiation caused tumors... They said that now, they will do hers every 4 years or so; or if she seems to be slipping in percentile for height. They did do the wrist scan, saying that it is the most reliable for monitoring the growth. If that IS the case, then I wouldn't want to see her get the full body scan, either, with the risk factor she has of recurrence. Hope that helps in some way. Sorry I can't direct you to any published data, never had to look it up for her; but you might even get some piece of mind, just finding out where your son falls, in the percentile rating... if he's on par with other kids at 19 mos, then you'll know, that his growth should be progessing well. Best of luck, Janine