A family member, a 36-year-old female, had thyroid surgery followed by iodine-131 therapy three years ago. Recently she had a whole-body PET (positron-emission tomography) scan, which came out clear. She wants to have a baseline mammogram done, and she would like to know how long she should wait after her PET. She is concerned with the added radiation dose/risk.
She needs to wait until the next day, when all the fluorine-18 has decayed away. But besides that, there is no reason to wait to have a mammogram. The radiation doses from mammograms are small and unimportant as far as risk.
Diagnostic exams should not be a concern following iodine-131 therapy. It is important to have screening scans for cancer and any other diagnostic exams that her physician feels are needed for her ongoing post-therapy care.
Carol S. Marcus, PhD, MD
Professor of Radiation Oncology and of Radiological Sciences, UCLA
Marcia Hartman, MS
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