PET scan preparation
Preparing for a — Cardiac or Brain PET Scan
You have been sent for a PET scan by your cardiologist or neurologist — not by an oncologist. The preparation, especially for a cardiac scan, is more involved than most patients expect, and arriving with it done correctly makes the scan worth having.
Medically reviewed by Dr. T. Raghavender Reddy, Medical Oncologist, MBBS · DM (Medical Oncology) · MD (Radiation Oncology) · Last reviewed September 2026
- Not a cancer scan — Cardiac and brain PET scans look at heart function and brain activity, not tumours. You are here for a heart or neurology investigation.
- Diet matters more than you expect — For cardiac PET, what you eat in the day or two before changes what the scan can see. Fasting alone is not enough.
- Caffeine rules apply — Caffeine affects how the heart and brain respond during these scans. Your instruction sheet will say exactly when to stop it.
- Follow your specific sheet above all else — Preparation varies by tracer, scanner and scan purpose. General advice online is a guide only — your instruction sheet is the authority.
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Cardiac and brain PET scans require stricter preparation than most imaging. A cardiac scan usually needs a special high-fat, very low-carbohydrate diet for the day or two before — not fasting alone — and caffeine is typically stopped beforehand. A brain PET mainly needs fasting and quiet rest. Your imaging team will give you the exact rules for your scan.
CION does PET-CT in Hyderabad from Rs 10,499 — among the lowest published prices in the city, with no hidden charges. Indicative price, as of September 2026.
How is cardiac PET preparation different from other scans?
Most imaging scans ask you to fast for a few hours. A cardiac PET scan goes further — your diet in the full day or two before the scan is as important as the fast itself.
Your team will ask you to eat a high-fat, very low-carbohydrate diet in the days before. Eggs, paneer, cheese, butter, cream and unseasoned meat are typically allowed. Rice, roti, chapati, dal, fruit, potatoes and any sugar or sweetened drink are not. This matters because the radioactive tracer used in cardiac PET behaves like glucose in the body. Shifting your heart away from glucose before the scan is what makes the image readable.
This scan has been requested by your cardiologist or neurologist, not as part of cancer care. What it finds — and what it means for you — will be explained by the specialist who referred you. The imaging team will verify your preparation on the day, but clinical responsibility for interpreting the result stays with your referring doctor.
What does preparation for a brain PET scan involve?
Brain PET scans are used to assess conditions such as memory problems, seizure disorders and certain movement disorders. The preparation is simpler than cardiac prep, but it still requires care.
You will be asked to fast before the scan. On the day, avoid strenuous physical activity and try to stay mentally calm — the tracer reflects how active your brain is at the moment it is given. The hour before the scan is usually spent quietly in a dimly lit room, without screens, music or conversation.
Caffeine is typically stopped on the day of the scan. If you take regular medication, ask your referring neurologist before the appointment whether anything needs to be paused. Bring a full list of everything you are taking, including supplements and any herbal preparations.
PET-CT Partner Centres
PET-CT Scan Centres in Hyderabad
CION offers PET-CT scans through 4 trusted partner PET-CT centres across Hyderabad, so you can choose the one closest to you. Call 18002028726 and we’ll guide you to the earliest available appointment.
PET-CT Centre — Punjagutta
PET-CT Centre — Himayatnagar
PET-CT Centre — Narayanaguda
These are partner diagnostic centres within the CION network. Toll-free booking: 18002028726.
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What should you do before your scan?
Read your instruction sheet the day you receive it
Preparation for cardiac PET often begins two or more days before your appointment. Brain PET preparation typically starts the evening before. Do not leave reading the sheet until the night before.
Stop caffeine at the time stated
Tea, coffee, cola and energy drinks all count. For cardiac scans, caffeine can affect the stress component of the test. For brain scans, it can alter the baseline activity the tracer measures.
Switch to the cardiac diet if instructed
This step applies to cardiac PET only. From the evening your sheet specifies, eat high-fat, very low-carbohydrate meals. Eggs, paneer, cheese, butter, cream and non-starchy vegetables are typically allowed. Rice, roti, dal, fruit, potatoes, sugar and sweetened drinks are not.
Fast from the time your sheet specifies
Plain water is usually permitted. Do not eat, drink anything other than water, or chew gum during the fasting period. Do not take glucose-containing medicines without first checking with your team.
Check your medicines with the referring doctor before the day
Do not stop any regular medication on your own. If you are unsure whether beta-blockers, diabetic medicines or any supplement needs to be paused, ask before the day of the scan — not on the morning itself.
Arrive early and bring your referral letter
Your blood glucose will be checked before the tracer is given. If preparation has not been followed correctly, the team will tell you whether the scan can go ahead. Bring the instruction sheet and your referring doctor's letter.
Did you know?
The tracer used in most cardiac PET scans behaves like glucose in the body. When the heart is running on carbohydrates, it takes up the tracer everywhere — making it impossible to see which areas are struggling.
Eating a high-fat, very low-carbohydrate diet before the scan shifts the heart to burning fat instead. The tracer then concentrates only where the heart cannot make that shift, which is the information your cardiologist is looking for.
Source: EANM procedural guidelines for myocardial FDG PET imaging
A whole-body PET-CT at CION is Rs 10,499 — among the lowest published prices in Hyderabad — with a free Rs 950 oncologist consultation to talk through your report. Indicative price, as of September 2026.
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Common questions
Frequently asked questions
My cardiologist sent me for a PET scan. Does that mean I have cancer?
No. A cardiac PET scan is used to assess how your heart muscle is working — looking at blood flow, areas of damage, or how much heart tissue is still alive after a heart attack. It is requested by cardiologists, not as part of cancer investigation. Being sent for a PET scan to a centre that also treats cancer can feel alarming, and we understand that. The scan itself has nothing to do with cancer, and the result will be interpreted by the team your cardiologist instructs.
Can I have my morning chai or coffee before the scan?
Not for most cardiac PET scans, and usually not on the morning of a brain PET scan either. Caffeine can affect how the heart responds to some components used during cardiac scanning, and for brain PET it can alter the baseline activity the tracer measures. Your instruction sheet will say exactly when to stop — that time is typically well before the morning of the scan, not just a few hours before. Stop from that point, not just from when you wake up.
What if I accidentally ate the wrong thing before my cardiac PET?
Tell the imaging team before the scan starts. Your blood glucose will be checked before the tracer is given, and a high reading will usually flag the issue anyway. If preparation has not been followed correctly, the scan may need to be rescheduled. That is frustrating, but a poorly prepared cardiac PET can produce images that are difficult to interpret or actively misleading. The team will not judge you. They will tell you what the next step is.
How far in advance does the special diet for cardiac PET start?
For most cardiac PET protocols, the low-carbohydrate, high-fat diet begins the evening before the scan — though some protocols start earlier. Your specific instruction sheet will give you the exact time. If you have not received an instruction sheet, call the imaging centre before your appointment and ask for one. Do not rely on general information from the internet; protocols vary between centres and between different types of cardiac scan.
Is the injection safe? What about the radiation?
The radioactive tracer is given as a small injection and leaves your body within hours. The radiation dose from a PET scan is within the range that the International Atomic Energy Agency (IAEA) and other nuclear medicine bodies consider acceptable for a diagnostic study — meaning the clinical information it provides justifies the exposure. The tracer does not make you feel different and is not the same as a CT contrast dye. If you have had a reaction to any imaging agent before, mention it to the team before anything is given.