PET-CT scan: what should you know?

A healthcare professional gives a radiotracer, often FDG, through an injection. You then rest so the tracer can distribute before lying on the scanner table. PET detects where the tracer collects, while CT supplies a detailed map of organs, bones and other structures. The combined images can help locate active disease, compare a current scan with earlier imaging and support treatment decisions. Uptake is not specific to cancer: infection, inflammation, recent exercise and healing may also affect the picture. A specialist reads the study with your symptoms, examination and other tests.

Read the appointment instructions carefully. You may need to avoid food for a period, drink water and limit strenuous exercise. Tell the department about diabetes, pregnancy, breastfeeding, medicines and previous reactions to injected substances. Keep warm and relaxed if advised, since muscle activity can influence the images. Wear simple clothing and expect to remain still during acquisition. Drink fluids afterwards if your team recommends this. The [FDG Radiotracer](/materials/fdg-radiotracer/) page explains the material, while [PET-CT Scan](/treatments/diagnostics-and-staging/pet-ct-scan/) covers the procedure in more detail.

Alert staff at once if you develop breathing difficulty, throat or facial swelling, severe dizziness or collapse during the appointment. Afterward, seek urgent care for chest pain, severe breathlessness or fainting. Contact the imaging service if you have persistent vomiting, a spreading rash, or increasing redness and pain where the injection was given. These warning signs call for clinical assessment and do not indicate what the scan shows. For results, wait for the clinician responsible for your referral to explain the complete report.

Ask what question the scan is answering, whether your medicines or blood glucose need special handling, whether contrast is planned, and how soon the findings will guide care. You can ask how a [PET-CT Scanner](/technology/pet-ct-scanner/) differs from other imaging and whether the scan is relevant to [Lymphoma](/conditions/lymphoma/) or [Cancer of Unknown Primary](/conditions/cancer-of-unknown-primary/).