A PET CT scan combines two scans in one visit to show both how your body looks and how your cells are working. Learn its uses, process and safety in simple words.
A PET CT scan is an imaging test that joins a PET scan (which shows how active your cells are) with a CT scan (which shows body structure) in one session. Doctors mostly use it to find, stage and track cancer, and to check the brain and heart.
How Does a PET CT Scan Work?
Before the scan, you get a small injection of a radiotracer. The most common one is FDG, a form of sugar with a tiny radioactive tag. Cells that use a lot of energy, such as many cancer cells, absorb more of it. The PET part detects this signal, and the CT part takes X-ray pictures of the same area. A computer fuses both into one image.
Part of the scanWhat it showsSimple examplePETCell activity (metabolism) using a tiny amount of radioactive sugarCancer cells use more sugar, so they appear brightCTDetailed body structure and exact locationShows the size and place of a lumpPET CT togetherActivity and location in one imageTells the doctor if a lump is active and exactly where it sitsWhy Do Doctors Advise a PET CT Scan?
- Cancer diagnosis and staging: to see if cancer has spread. Read more in our guide on PET CT for cancer detection and staging.
- Treatment response: to check if chemotherapy or radiotherapy is working.
- Recurrence check: to look for cancer coming back after treatment.
- Brain conditions: such as memory loss or epilepsy. See PET CT brain scan.
- Heart health: to check if heart muscle is still alive after a heart attack.
- Infection or inflammation: when fever has no clear cause.
How to Prepare for a PET CT Scan
- Do not eat for 4 to 6 hours before the scan. Water is allowed.
- Avoid heavy exercise for 24 hours, as it can change how muscles take up sugar.
- Tell the staff if you have diabetes. Your blood sugar needs to be in a safe range. See our guide on PET CT preparation and diabetes.
- Wear loose clothes without metal and carry your old reports.
- Inform the team if you are pregnant or breastfeeding.
What Happens During the Scan?
- Your blood sugar is checked and the tracer is injected into a vein.
- You rest quietly for about 45 to 60 minutes while the tracer spreads.
- You lie on a table that slides through a ring-shaped scanner for about 20 to 30 minutes.
- You can go home soon after, and you may be told to drink water to help flush the tracer.
The whole visit usually takes 2 to 3 hours. Read the full process in PET CT procedure step by step.
Is a PET CT Scan Safe?
The tracer contains a very small amount of radiation, and it leaves your body within hours. The scan is done only when the benefit is greater than the small risk. Allergic reactions are rare. Learn more in PET CT radiation and safety.
PET CT Scan vs Other Scans
A CT or MRI mainly shows structure. PET CT adds function, so it can find disease earlier in some cases. Compare them in PET CT vs CT scan and PET CT vs MRI.
Understanding Your Report
The report describes bright areas of uptake and gives a number called SUV. A high SUV does not always mean cancer, because infection and inflammation can also be bright. Your doctor will connect the report with your other tests. See PET CT report and SUV values.
Frequently Asked Questions
What is a PET CT scan used for?
It is mainly used to detect and stage cancer, check treatment response, find recurrence, and evaluate brain and heart conditions.
Is PET CT scan painful?
No. You feel only a small needle prick for the injection. The scan itself is painless.
How long does a PET CT scan take?
The scan takes 20 to 30 minutes, but the full visit including rest time is about 2 to 3 hours.
Can I eat before a PET CT scan?
No. You usually need to fast for 4 to 6 hours. You can drink plain water.
Is PET CT scan safe?
Yes, when advised by a doctor. The radiation dose is small and the tracer leaves the body within hours.
Can diabetic patients have a PET CT scan?
Yes, but blood sugar must be controlled. Tell the staff your medicines so they can guide you. See PET CT for diabetic patients.
Does a bright spot always mean cancer?
No. Infection, inflammation and healing tissue can also show uptake. The doctor reads the result along with your history.
When will I get the PET CT report?
Reports are usually ready within 24 to 48 hours. Ask the centre for the exact time.
How much does a PET CT scan cost?
Price depends on the tracer, body area and centre. See PET CT scan cost factors in Delhi or contact us for current rates.
Book Your Test at Ganesh Diagnostic
Ganesh Diagnostic & Imaging Centre in Rohini, Delhi offers this test with trained radiology staff and clear reports. You can book an appointment online, check our branches across Delhi NCR, contact us for current rates, or explore all our services.
This article is for general information only. It does not replace advice from your doctor. Always follow your doctor's instructions for your test.
