It's My Understanding That So-called "health Scans" (full Body Screening

It's my understanding that so-called "health scans" (full body screening CT, typically performed at the request of an asymptomatic patient, and paid for by same) subject patients to less radiation than typical medically necessary diagnostic CAT scans. Can you please tell me the approximate radiation dosage one would receive from one of these so-called "health scans"? Thank you.