DEAR DR. ROACH: I had a pituitary tumor that was discovered over 25 years ago. For years, I had an MRI with and without dye every six months. Then it changed to once a year. Can you get damage from too many brain MRIs?

— D.J.

ANSWER: An MRI uses powerful magnetic fields to take pictures of the body, and the resulting detail of soft tissue (such as the brain) is generally more helpful than a CT scan. Furthermore, MRI does not use ionizing radiation, so there is not a risk of cancer as there is from excess X-rays and CT scans (although the risk of cancer from X-rays and CT scans is probably small).

There has been concern about the MRI dye, called gadolinium. Some gadolinium dyes have been found to accumulate in the brain as well as other organs such as the bone and the liver. There is, as of yet, no clear harm that has been identified with gadolinium accumulation; however, clinicians should consider whether contrast is really necessary. The Food and Drug Administration requires patients receive educational information prior to receiving gadolinium contrast.

Some gadolinium contrast agents are more likely to cause accumulation than others. In particular, macrocyclic gadolinium-based contrast agents are less likely to be retained. In your case, the interval was probably changed due to so many years of being stable; the tumor is unlikely to grow.

DEAR DR. ROACH: I am a 92-year-old male with a number of ailments including psoriasis, chronic obstructive pulmonary disease and congestive heart failure. I have had several medical procedures, including prostate surgery, valve replacement and stents.

Please clarify the term “brain fog.” How would I know if I had this?

— P.G.

ANSWER: “Brain fog” refers to difficulty with brain function, especially trouble with thinking clearly, trouble with concentration and memory changes. Many medical conditions can cause this, including acute delirium, dementia and medications. I have recently heard the term being used to describe what many people feel after a bout of COVID, particularly severe COVID. The term is also used to describe cognitive symptoms associated with chronic fatigue, sleep disorders, migraine and several other conditions.

Only you can tell if you have had this as there are no tests that can be done to determine if a person has brain fog. I think it differs from the changes that happen to people as they age, as these symptoms are more sudden.