PET-CT Scanner and Cancer Imaging

A PET-CT scanner combines a tracer-based picture of body activity with CT images that show anatomy and location.

A healthcare professional gives the tracer, usually through a vein, and allows time for it to distribute. You then lie still on a narrow couch that moves through the scanner. The scan itself is quiet and does not involve the machine touching your body. Preparation may include fasting or changing usual medicines, so follow the instructions from the imaging team.

Tracer activity is not specific to cancer. Infection, inflammation, healing, some medicines, and normal activity in certain organs can also change the image. Very small areas or tumours with low tracer uptake may be less visible. CT findings also have limits. A PET-CT result is interpreted with your symptoms, examination, prior scans, and other tests; it does not by itself establish every diagnosis.

Depending on the clinical question, your team may use CT, MRI, ultrasound, or a bone scan instead of or alongside PET-CT. MRI is useful for detailed soft-tissue views in selected body regions, while ultrasound can assess some organs without ionising radiation. The choice depends on the area being assessed, the question being asked, and your health details.

Plan to rest quietly after the tracer is given and keep your body still during imaging. Drink fluids if the team advises this, and ask when you may resume normal activities. Tell staff about pregnancy, breastfeeding, diabetes, allergies, kidney problems, or difficulty lying flat before the appointment. The report is reviewed with the rest of your clinical information.

PET-CT involves a small radioactive tracer exposure and X-rays. The tracer leaves the body over time, mainly through urine. Follow any specific instructions about contact with infants or pregnant people. Tell the team about possible pregnancy and medicines affecting blood sugar, because preparation can need adjustment.