Harvard Health Letter

By the way, doctor: PET-CT scans for finding breast cancer

Q. I've been having PET-CT scans to look for any growth or spread of previously removed tumors. Are they as reliable in detecting breast cancer as a regular mammogram?

A. The short answer is no, PET-CT scans are not suitable substitutes for mammograms. Mammograms take advantage of the fact that most of the female breast is fat tissue, so it's relatively transparent to the low doses of radiation used in mammography. Very subtle changes in tissue architecture are apparent on a mammogram, as are small deposits of calcium that may in some cases signal the growth of a tumor. Today's mammograms can find lesions that are less than 1 centimeter (about half an inch) in diameter.

PET-CT scans do two things. Positron emission tomography (PET) uses glucose that has been tagged with radioactive molecules to identify tissue that's metabolically active. Many tumors have high rates of metabolism, so they tend to "light up" on a PET scan. Like a mammogram, computed tomography (CT) uses radiation, but it takes multiple views of a body part and assembles them into a detailed picture that can show the location and size of a cancerous growth.

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