Medical Oncologist
CION Cancer Clinics
The mapping scan before Y-90, and why it is needed | CION Cancer Clinics
The mapping scan is a rehearsal for Y-90. A harmless tracer is put into the liver arteries, and a scan shows where it travels. This tells the team whether the radioactive beads would stay in the liver or leak to the lungs, stomach or bowel. It also helps them work out the dose. This page explains what happens, what the results mean and why it cannot be skipped. At CION Cancer Clinics, a multidisciplinary tumour board weighs your liver function and your scans before recommending any treatment.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed October 2026, next review due October 2027
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The short answer
Why do I need a mapping scan before Y-90?
The mapping scan shows exactly where Y-90 beads would go before any radiation is given. It checks that they would stay in the liver tumour and not drift to the lungs, stomach or bowel, where they could cause harm. Without it, Y-90 is not safe to give.
Doctors may call it a mapping angiogram, a planning study, an MAA scan or a shunt study. They all mean the same rehearsal. It is usually done a little before the real treatment, as a separate visit.
Who this page is for
This page is for people with liver cancer, whether it started in the liver or spread there, who have been offered Y-90 (also called TARE or radioembolisation). If you are still deciding whether Y-90 suits you, start with who is suitable for Y-90. The technique of the treatment itself is covered on our Y-90 radioembolisation page.
A mapping scan is not a treatment. Nothing radioactive enough to treat the cancer is given that day.What it looks for
What exactly does the mapping scan check?
It answers four questions that decide whether Y-90 is safe, and how it should be given.
Which arteries feed the tumour
Liver arteries vary a lot from person to person. The angiogram draws a map of yours, so the beads can be placed in the right branch on treatment day.
How much would reach the lungs
Some liver tumours have abnormal channels that let blood pass straight through to the lungs. If too much would travel there, the radiation could damage the lungs. This is called lung shunting.
Whether any flows to the gut
Small arteries near the liver sometimes supply the stomach, duodenum or pancreas. Beads reaching these could cause painful ulcers. The radiologist looks for them carefully.
What can be done about it
- Block the small vessel with a tiny coil
- Place the catheter beyond it on the day
- Choose a different treatment if neither works
How to work out the dose
The scan shows how the tracer spreads between tumour and healthy liver. The team uses this, with your CT or MRI, to plan a dose that targets the tumour while sparing the rest.
Not sure whether this applies to you?
Ask an oncologistOn the day
What happens during a mapping scan?
Preparation
You will be asked not to eat for a few hours beforehand. Bring your scans, blood reports and a list of every medicine you take, including blood thinners and any herbal products.
The angiogram
Under local anaesthetic, a thin tube is passed through an artery in the groin or wrist up to the liver. Dye is injected and X-ray pictures map the arteries. Small vessels to the gut may be closed off.
The tracer
A tiny amount of a harmless radioactive tracer, called MAA, is put into the liver artery. The particles are about the same size as Y-90 beads, so they travel the same way.
The nuclear medicine scan
You are moved to a gamma camera, which shows where the tracer has settled. Most people go home the same day, after a period of lying flat so the artery can seal.
On your report
What do the words on a mapping report mean?
- MAA
- Macroaggregated albumin. Tiny protein particles tagged with a small amount of radioactivity, used as a stand-in for Y-90 beads.
- Lung shunt fraction
- The share of the tracer that passed through to the lungs. A low figure is reassuring. A high one may mean a lower dose, or no Y-90.
- Extrahepatic uptake
- Tracer seen outside the liver, often in the stomach or bowel. It needs explaining before treatment can go ahead.
- Coil embolisation
- Closing a small artery with a tiny metal coil, so beads cannot reach an organ they should not.
- SPECT-CT
- A gamma camera picture combined with a CT, which shows exactly where in the body the tracer has settled.
- Dosimetry
- The calculation of how much radiation to give, and where, based on the mapping and your liver volume.
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Commonly believed
What do families often get wrong about the mapping scan?
"The mapping scan is the treatment."
It is only a rehearsal. The tracer does not treat the cancer. Y-90 itself is given at a separate visit, once the results have been reviewed and the dose planned.
"It is an extra test the hospital adds to raise the bill."
International practice treats it as an essential safety step. Skipping it would risk radiation damage to the lungs or gut, which can be serious and hard to treat. Ask for it to be shown separately on your written estimate.
"If the mapping is bad, nothing else can be done."
A poor result rules out Y-90, or changes the dose. It does not rule out other treatment. TACE, medicines or radiation from outside the body may still be options.
"The tracer will make me radioactive to my family."
The amount is very small and fades quickly. Your team will tell you if any simple precautions apply. Most people need none after a mapping scan.
Being straight with you
What this page cannot tell you
It cannot read your mapping report. The figures on it only make sense alongside your CT or MRI, your liver blood tests and the type of beads planned. Your interventional radiologist and nuclear medicine doctor interpret it together, and the tumour board decides what happens next.
It cannot tell you which centre does it
Mapping and Y-90 need interventional radiology and nuclear medicine in the same place, and few centres in India offer both. CION coordinates them through accredited partner hospitals. Your team will tell you where each step takes place, and the cost is quoted separately.
Who this does not apply to
If you have been offered TACE, ablation or surgery rather than Y-90, you will not need a mapping scan. TACE uses a different approach and does not need this rehearsal.
If anything on your mapping report worries you, bring it to a CION medical oncologist. We will explain it in plain words.Questions we are asked
Common questions about the mapping scan
Is the mapping scan painful?
Most people feel only the sting of the local anaesthetic where the tube goes in. You may feel warmth when the dye is injected. A sedative is often given to help you relax. Some people have a little bruising or soreness at the puncture site for a short while afterwards.
Will I need to stay in hospital?
Usually not. Most people go home the same day, after lying flat for a while so the artery seals. If you travel from a district far from Hyderabad, ask whether an overnight stay nearby would be wise. Someone should accompany you home.
How soon after mapping is Y-90 given?
It varies. The beads are ordered and the dose is calculated for you after mapping, which takes some time. Some centres do both on the same day for selected patients. Your team will give you the plan once results are reviewed.
What if too much tracer goes to my lungs?
The team may lower the dose to keep the lungs safe, or decide Y-90 is not suitable. If Y-90 is ruled out, other options such as TACE or medicines are discussed. The page on lung shunting explains this result in more detail.
Do I need to stop my blood thinners?
Possibly, because the procedure goes through an artery. Never stop them on your own. Tell the team about every medicine you take, and they will give you clear instructions about what to stop, when, and when to restart.
Can the mapping scan be repeated?
Yes, if the first one is unclear, if a long time passes before treatment, or if the plan changes. A repeat is not a sign that something went wrong. It is simply to make sure the map still matches your liver before radiation is given.
Is the dye safe for my kidneys?
For most people, yes. If your kidney function is reduced, or you have diabetes, the team checks your blood tests first and may give fluids. Tell them about any past reaction to contrast dye or iodine.
Who should I ask about my results?
Your interventional radiologist and the doctor leading your liver cancer care. If you want an independent look, a CION medical oncologist can review the report with your scans. Call the helpline and someone will arrange it.
Your Specialists
Meet CION's liver cancer specialists. Bring your scan reports and liver blood tests.
Our medical and surgical oncologists plan liver cancer care together, weighing the tumour and how well your liver works before choosing surgery, a liver-directed procedure or medicines.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
Medical Oncologist
Medical Oncologist
Surgical Oncologist
Dr. Muralidhar Muddusetty
MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
Surgical Oncologist
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Sources
- RadiologyInfo.org (RSNA/ACR) — Radioembolization (Y90)
- American Cancer Society — Embolization Therapy for Liver Cancer
- Cancer Research UK — Treatment for liver cancer
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
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Talk to us
Been told you need a mapping scan and not sure why?
A CION medical oncologist can go through your scans and the plan with you, and explain what the mapping result means for your treatment. One helpline serves every CION centre.