Dear Dr. Roach: I have a 3 mm piece of shrapnel lodged in my skull bone. This is a result of military action back in 1967. A recent X-ray continues to show the shrapnel after all these years. I would say that the piece is half in and half out of the skull bone.

At age 77, I am unable to have an MRI. I currently have Type 2 diabetes and a pacemaker. I also had prostate cancer, which is now post-radiation, and I have also had a stroke and a heart attack. Although I do not need an MRI right now, I am being proactive because I am concerned that I may need one in the future due to my medical conditions.

Should I have the shrapnel removed to allow for a future MRI? Although doctors tell me that a CT scan is as good as an MRI, I believe an MRI is always the better option. Or if I need an MRI, can I leave the shrapnel in place? — T.

Answer: Thank you for your service. Although I admire your proactive nature, removing shrapnel from your skull bone is too risky to consider just for the prospect of maybe needing an MRI someday. While it is true that MRIs have many advantages over CT scans for some purposes, a CT scan is better for some medical indications and nearly as good for most.

It’s likely that the shrapnel is steel- or iron-containing, and these can move in the strong magnetic field of the MRI if they are not firmly attached. Even if they are firmly attached, as it sounds like yours is, ferromagnetic metal (iron, nickel, cobalt and a few others) can heat up and cause pain and even tissue damage. So, a radiologist would be unlikely to perform an MRI on you.

Modern pacemakers (after the year 2000) are made with materials that are safer to use in an MRI scanner. A 2020 review of MRI scans done on people with older pacemakers (even before they were made safer) found that there were no complications to the patients or devices, so MRI scans can typically be performed on people with pacemakers.