MRI: Gadolinium Contrast
https://www.uwmedicine.org/sites/stevie/files/2020-03/MRI-Gadolinium-Contrast.pdf
Is Gadolinium really ferromagnetic?
Gadolinium is accepted to be one of the four ferromagnetic elements
https://www.nature.com/articles/43363
My point being(which I think you picked up on) is, if they can inject you with a magnetic material, then you can be injected with "nanobots/ metallic" material…