As far as I can tell, it’s not higher dose.

> It was scanned on a GE Revolution CT machine. The scan was performed using technique optimized for human extremities, and employed very thin slice thickness of 600 microns.

No level of radiation exposure is safe. How much of CT radiation is considered acceptable depends on the application.

Dose response being linear no threshold is the operating assumption. Radiation hormesis may be a thing but it’s difficult to be certain at low doses.

https://en.m.wikipedia.org/wiki/Radiation_hormesis