MRI scans/thymectomy in the 1980s

Hi,
I have MG and was diagnosed with it in 1984 at the age of 15. I had a thymectomy in 1985 which worked wonders and had an immediate positive effect.
Now over 40 years later i have to have a brain scan - an MRI - which is unconnected with MG. My question is has anyone else had an MRI after having a thymectomy? There is a lot of metal in my chest now and i don't know what kind of metal it is !
I have spoken to a radiologist today who thought it should be fine - but neither he nor i know what metal waa used and i am concerned about going ahead with it.