How to prepare for your PET/CT scan

Good preparation is not a formality. A scan done on an unprepared patient can be genuinely unreadable, and repeating it means another dose of radiation and another anxious week. Twenty minutes of care the night before protects the whole study.

The day before

Do not exercise. No gym, no long walks, no heavy physical work for 24 hours before the scan. Muscle that has been working absorbs the tracer enthusiastically, and a lit-up shoulder or thigh can obscure the very lymph node your doctor is asking about.

Eat a low-carbohydrate dinner. Avoid rice, roti, bread, sweets, fruit juice and sugary drinks. Protein and vegetables are ideal. This keeps your blood sugar low, which lets the tracer go to the tissue we are interested in rather than being diluted everywhere.

Stay warm. In cold weather your body burns energy in a tissue called brown fat, usually around the neck and shoulders, and it shows up brightly on the scan. Keep warm the night before and on the way in.

Fasting

Six hours, nothing but plain water.

That means no tea, no coffee, no milk, no chewing gum, no toffees, no juice — not even sugar-free ones, because the sweeteners can still trigger an insulin response.

Plain water is the exception, and it is actively encouraged. Drinking well helps the tracer distribute properly and helps you flush it out afterwards. Do not turn up dehydrated.

If your appointment is in the morning, fast overnight. If it is in the afternoon, have an early light low-carbohydrate breakfast and then stop.

Medication

Take your regular medicines as usual, with plain water, unless we have told you otherwise. Blood pressure tablets, thyroid tablets, heart medication — carry on.

Tell us in advance about:

• Diabetes medication and insulin. This matters a great deal — see below.
• Steroids, which change how inflammation appears.
• Recent chemotherapy. Scans are usually best at least 10 days after a cycle.
• G-CSF injections (Neupogen, Grafeel and similar), which light up the entire bone marrow. We normally wait about two weeks.
• Blood thinners, if a biopsy is planned in the same visit.
• Any recent surgery or radiotherapy, with dates.

Never stop a prescribed medicine on your own before a scan. Call us and ask.

If you are diabetic

Diabetes does not stop you having a PET/CT. It just needs planning, so please tell us when you book.

• We usually give diabetic patients a morning slot.
• Your blood sugar should ideally be under 200 mg/dL at the time of injection. Higher than that and the sugar in your blood competes with the tracer, dimming the whole scan.
• Short-acting insulin must not be taken within about four hours of the injection, because it drives tracer into muscle instead of tumour. Metformin is usually continued, though for some abdominal studies we may ask you to pause it.
• Bring your glucometer and your usual medication with you, and something to eat for immediately after the scan.

We will give you exact instructions for your particular regimen when we confirm your appointment — please do not improvise from a general guide.

What to bring

• All previous scans on CD or DVD — the actual image files, not just the printed films or the report. Comparison with your old scans is often what makes the new one meaningful.
• Every previous report, however old.
• Biopsy and histopathology reports, and slides if you have them.
• Recent blood reports, including creatinine if contrast CT is planned.
• Discharge summaries and your treatment record — which chemotherapy, how many cycles, when.
• Your doctor's prescription for the scan.
• Insurance or TPA paperwork, if you are claiming.
• A relative or friend. Not compulsory, but the day is easier with one.

What to wear

Loose, comfortable clothing with no metal — no zips, hooks, buttons or metallic thread in the area being scanned. Leave jewellery, chains and watches at home rather than in a locker. You may be given a gown to change into.

During the waiting hour

After the injection you rest for 45 to 60 minutes while the tracer distributes. This is not idle waiting; what you do here shapes the images.

• Stay still and relaxed. Do not walk around, do not talk more than necessary, do not chew.
• Do not read or use your phone if it is a brain scan — visual and mental activity lights up the corresponding parts of the brain.
• Keep warm.
• Empty your bladder just before the scan starts.

Tell us in advance if

• You are pregnant, or think you might be. PET is generally avoided in pregnancy.
• You are breastfeeding. It is usually manageable, but the feeding schedule needs adjusting and we need to know beforehand.
• You are claustrophobic. The PET/CT ring is short, wide and open at both ends, and almost everyone who dreads it copes well — but tell us and we will talk you through it first.
• You cannot lie flat, or lying still is painful. Take your pain medication before you come and let us know; positioning can be adapted.
• You have kidney disease or have had a reaction to contrast dye before.

How long it takes

Plan on about two and a half hours in the centre. Preparation and check-in take around fifteen minutes, the injection two, the resting hour about sixty, and the scan itself roughly fifteen on our digital scanner — where a conventional machine would take twenty-five to thirty.

Afterwards

Eat normally straight away. Drink plenty of water for the rest of the day and empty your bladder often; that is how the tracer leaves your body.

For the rest of the day, keep a reasonable distance from pregnant women and small children — a precaution, not an emergency. By the next morning there is nothing to think about.

If anything here is unclear, call us on +91 93169 25516. It is a much better use of a phone call than arriving unprepared.