My wife has two replacement knees with about 500g of titanium in each, and security screening at airports is a right PIA for her.
The problem is that there doesn't appear to be any system or procedures in place for screening people with hip and knee replacements or steel plates in their skulls.
Every security operator seems to approach the "metal in body" issue with a different attitude.
Some security screeners are quite happy to be informed that she has artificial knees, at which point there is an "O.K." from the screener, and a quick scan and patdown ensues, and she's right to go.
Other security screeners promptly treat her like a terrorist, refuse to accept the explanation, and give her the "works".
It's high time a system was implemented whereby people with metal in the bodies can get a doctors certificate to present to security staff, which would then be accepted, and a simple scan carried out to allow the person to proceed - without the 3rd degree treatment.
Some of the security screeners are particularly officious - it's obvious they aren't picked for their "inter-personal skills".