One obvious alternative plan, presupposing that Full Body Scan is dirt cheap, is the following protocol:

- At 25 years old or whatever you get a FBS. Pretty much no matter what, this FBS will not be used to do more checks, procedures, and so on.

- ... and now we give you another FBS every so-many years, and only those things that are different from the previous scan are investigated.

There's still an issue with needless procedures, but the amount of 'weirdness that are not going to cause an actual issue had the patient never been aware' is significantly reduced by looking only at changes. i.e. most 'weirdness' shows up early and is fairly stable.

The difficulty is the moral issue. You cannot show that first scan to the patient. Even if every soul agrees beforehand that the rule is that nothing on that first scan, no matter how scary it looks, is further investigated... any medical issues raised by patients are used as a major information input for diagnosing issues. If I show a patient a scan that has this tumor looking thing on the left lung, then no doubt a few months later they'll be back complaining about shortness of breath and a pain on the left side of the torso. The mind is a powerful thing. At that point you can do a scan and see... the same nasty tumor looking thing we saw on that first FSB, and we're right back to the issue of these scans doing more harm than good.

Is it morally acceptable to hide that first scan from the patient?