Dear Dr. Roach: My primary care physician scheduled me for a cardio stress test and ultrasonography with intravenous “microsphere” imaging. I’m slightly concerned about the term “microsphere.” Is this a safe procedure? Are there any complications stemming from this chemical/procedure? Should I be concerned about a stroke? How long do these microspheres stay in the body? Do they become a part of plaque? Are there other safer imaging methods? — K.O.S.

Answer: Intravenous microbubble contrast agents are made from compressed gas that is contained in a phospholipid or protein, which are both components of normal cells. They are used in an ultrasound to make the blood “brighter,” making it much easier to see blood movement and allowing for a greater resolution of the images.

Microspheres don’t leak into the tissue, so strokes and plaque aren’t real concerns. They stay in the body from 4-10 minutes, then spontaneously break up, with the gas being dissolved in the blood and the shell getting removed by normal processes in the liver. Unlike traditional dyes used for CT and MRI scans, they aren’t toxic to the kidneys, and there’s a lower risk of allergic reactions.

Dr. Roach Writes: A recent column on rosacea generated many letters from readers who offered advice. Therapies that worked for them included avoiding triggers, especially hot liquids. Several readers wrote in that once they stopped specific foods (wheat and peanut butter were specifically mentioned), their rosacea got better.

Other readers found relief with medications that are available over the counter, including benzoyl peroxide, a common acne treatment; a proprietary cream with vitamin C and hyaluronic acid; and a cream containing azelaic acid. As always, I appreciate when my readers write in with “real world” suggestions.

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYour

GoodHealth@med.cornell.edu.