Grandfather came into close contact (e.g.sit lap) with young childs (1 year and baby) on the day he had a diagnostic mri ct/ pet scan? (i guess it was with tracer). could this give adverse affect on the childs? if so, which adverse effects possibly?

I know of no part agent used in that study that would pose a risk to anyone at any age who came into contact with them.

The contrast used for these scans are generally safe. Some patients experience an adverse reaction. Contact with children should not pose a safety concern.

There is no risk to the child from what you described. Wish you and your child good health!