A full body scan is not a good idea for someone with HA. I had a chest, abdo and pelvis CT scan that ended up showing a lump on my liver and fluid round my heart it worried me sick. Turns out the lump is a benign hemangioma and the fluid is so trivial the cardiologist took one look at my echo results and discharged me. Most people will have something found on a body scan that they wouldn't even know was there if they didn't have one and it causes more angst and worry than necessary. So, yes while a clear body scan would be great there's a good chance there would be incidental (benign) findings that would have you quaking in your boots for a couple of months while going through more needless tests to diagnose you.
Plus reassurance is only temporary for someone with HA, the fear cycle is just that a cycle and while you may be appeased for a few hours/days even months it will not cure HA.