I have Harrington Rods in my back due to scoliosis.?

19 years ago I had a scoliosis operation in which Harrington rods were attached to my spine. I was told they are steel rods. Well I'm 33 and I need an MRI. Will this be a problem? Yes, I did tell the doctor who has set up the MRI I have harrington rods and he said it won't be a problem. But I just want to make sure. If you can give me a sight to go to that would be great.