What should you know about PET scan use contrast?

FDG is a radiotracer that highlights areas using glucose actively. Contrast is a separate medicine that can make organs, blood vessels, or soft-tissue boundaries easier to distinguish on the CT part of the examination. A PET-CT can therefore be performed with FDG alone, with CT contrast, or with both, depending on the scan protocol.

Tell the team about previous reactions to contrast, kidney problems, diabetes, pregnancy or possible pregnancy, and medicines you take. A contrast decision is individual. The scan itself combines metabolic information with an anatomical map; an area that looks active still needs interpretation alongside symptoms, examination, and other tests.

Follow the imaging centre's instructions about fasting, drinking water, and medicines. Wear comfortable clothing and remove metal items when asked. The FDG injection is followed by a quiet waiting period so the tracer can distribute; keeping still and avoiding strenuous activity helps the images. If contrast is planned, staff may ask about allergies and kidney function and may explain whether it is swallowed or given through a vein.

During or after the appointment, promptly tell staff about trouble breathing, facial or throat swelling, widespread itching, severe dizziness, or pain and swelling at an injection site. These symptoms need immediate assessment. For ongoing vomiting, rash, or worsening discomfort after leaving, contact the imaging service or seek urgent medical care.

Ask which tracer and contrast, if any, are planned; whether you need to fast; how your kidney function or diabetes changes preparation; and when and how results will be explained.