PET-CT Whole Body (Oncology)
A focused scan for Whole-body metabolism, Tumour staging, Nodes.
Overview
Examines Whole-body metabolism, Tumour staging, Nodes. Performed at an NABL-accredited Meridian Health centre with a same-day report and a free doctor review.
The full panel
3 areas across 1 groupEvery parameter, grouped by body system — no clicking to expand.
What this scan measures
Metabolic activity across the whole body, fused with a CT for anatomical detail. A small amount of a radioactive glucose analogue (18F-FDG) is injected; tissues that consume glucose avidly — which most active tumours do — take it up and appear as bright areas, which are then localised precisely on the CT images.
PET-CT is primarily an oncology test. It is used to stage a known cancer, to look for spread that anatomical imaging alone would miss, to assess response part-way through or after treatment, to investigate a suspected recurrence when tumour markers rise, and occasionally to find the primary site when only a secondary deposit is known.
Symptoms that lead to this scan
- A newly diagnosed cancer requiring staging
- A rising tumour marker after treatment
- Assessment of response during or after chemotherapy
- A suspicious mass or enlarged nodes on another scan
- Cancer of unknown primary origin
Understanding your results
Uptake is quantified as an SUV, but a high SUV is not synonymous with cancer: infection, tuberculosis, sarcoidosis, recent surgery, inflammation and healing tissue all take up FDG strongly, and this is a particularly important caveat in India where tuberculosis is common. Conversely, some tumours are not FDG-avid and can look unremarkable. Brown fat, active muscle and the brain, heart, kidneys and bladder are normally bright and are not abnormal. A PET-CT is interpreted against your treatment history and previous scans, and a suspicious finding is generally confirmed by biopsy before it changes treatment.
Why the preparation matters
The preparation is the test. Fast for at least six hours and avoid all sugary drinks, because circulating glucose competes directly with the FDG tracer and a high blood sugar can make the whole scan uninterpretable — your glucose is checked before injection. Avoid strenuous exercise for 24 hours beforehand, since active muscle takes up tracer and creates confusing hot spots. After injection you rest quietly, without talking or reading, for around an hour while the tracer distributes. Keep warm on the day: shivering activates brown fat, which lights up brightly across the neck and chest.
PET-CT — safety and who should not be scanned
Full PET-CT guideThis is the highest-dose imaging study in routine use, and it is honest to say so plainly. It carries two exposures rather than one: the injected tracer, which irradiates from inside the body until it decays and is passed out in urine, plus the CT component. Published reference figures put the combined dose of a whole-body FDG PET-CT at roughly the natural background radiation an average person absorbs over several years — appreciably more than the CT alone. That is a trade worth making when the result will change cancer treatment, and not worth making otherwise, which is why PET-CT is a specialist request and never a screening test. Fluorine-18 decays quickly — its half-life is under two hours — so most of the activity is gone within a day, and drinking plenty of water and emptying your bladder often afterwards clears it faster.
- Pregnancy, or any chance of it
- The tracer crosses the placenta and the CT adds a direct dose, so PET-CT is avoided in pregnancy other than in genuinely exceptional circumstances. Declare it when you book, not on the day — a pregnancy test is often done before the injection, and once the tracer is in there is no undoing it.
- Breastfeeding
- Two separate issues, and the department will give you instructions covering both. Tracer can pass into breast milk, so milk is expressed and discarded for the interval your nuclear medicine team specifies — commonly around twelve hours for FDG — with milk expressed BEFORE the scan used for those feeds. Separately, and often the bigger dose to the baby, you remain mildly radioactive yourself, so prolonged close holding is limited for the rest of the day.
- Diabetes, or a high blood sugar on the day
- This one materially invalidates the scan rather than merely delaying it. FDG competes with your own glucose, so a high blood sugar means less tracer reaches the tumour and a scan that has cost you a full radiation dose can come back non-diagnostic. Blood glucose is measured before the injection and the scan is postponed above the threshold your department uses. Bring your full diabetes medication list and follow their timing instructions exactly — insulin given close to the injection drives tracer into muscle and away from the target, and metformin commonly causes intense bowel uptake that obscures the abdomen, so it is sometimes held for a day or two beforehand. Never change your own diabetes treatment without being told to.
- Reduced kidney function, if diagnostic CT contrast is used
- Many PET-CTs use a low-dose CT for localisation alone and need no contrast at all. Where a full contrast-enhanced CT is combined with it, every check that applies to an ordinary CT applies here too: a recent creatinine or eGFR, any previous reaction to iodinated contrast, and your medication list.
- Close contact with pregnant women and young children afterwards
- You remain a source of radiation for the rest of the day after the injection. Avoid prolonged close contact with anyone who is pregnant and with infants and small children for the period the department specifies, sit apart from others on the journey home, and do not bring a small child along as your companion to the appointment.
- Claustrophobia, or an inability to lie still for 20–30 minutes
- The PET-CT bore is longer than a CT gantry and the scan runs far longer, usually with the arms raised. Movement blurs the images and misregisters the PET against the CT, which can make the study uninterpretable. Say so in advance — positioning aids, arm supports and, where necessary, medication arranged with your doctor all work better than discovering the problem after the tracer has been given.
Who should consider this scan
- Patients with a confirmed cancer needing accurate staging
- Anyone being assessed for treatment response or recurrence
- Patients with a metastasis of unknown primary origin
- People with lymphoma, at diagnosis and after therapy
- Only where a specialist has indicated it — this is not a screening test
Conditions it helps detect
How it works
Patient stories
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