Your MRI scan: what it is like and what to ask

The scan almost everyone with a brain tumor has. What happens, how long it takes, what to do if small spaces frighten you, and what the dye is.

The short version

An MRI takes very detailed pictures of your brain. It uses a big magnet and radio waves. There is no radiation, and the scan itself does not hurt. It is loud, and you have to lie still. Most people also get a dye put into a vein part way through. You will have this scan more than once over time. That is normal, and it is how your team keeps track of what is going on.

What is an MRI?

An MRI is a scan that makes detailed pictures of the inside of your head. It uses a strong magnet, radio waves and a computer. It does not use x-rays or any other radiation.

For brain tumors it is the best scan there is, and it is usually the first one done.

A scan can show where a growth is, how big it is, and what it is doing to the tissue around it. It can often give your team a good idea of what type it is. What it cannot do is give you the name for certain. Only a piece of the tumor itself, looked at in a lab, can do that. If someone tells you they need tissue before they can say more, this is why.

Why am I having this scan?

There are three jobs, and the same machine does all three.

To find out what is going on. This is the scan that shows the growth in the first place.
To plan. Before surgery or radiation, your team needs a very exact picture of where it is. Extra sets of pictures are sometimes added to answer one specific question about the plan. The extra scans before treatment goes through them.
To keep watch. After treatment, scans are compared with each other over time to see what has changed.

The room, the machine and the noise are the same every time. What changes is what your team is looking for.

What happens, step by step

The safety form. Someone asks you a long list of questions about metal, devices and past surgery. Answer all of it, even the parts that seem silly. This is the step that keeps you safe.
Getting changed. You are usually given a gown. You take off jewelry, your watch, hearing aids, hair clips, coins, keys and anything with a magnetic strip.
The line in your arm. If you are having dye, a nurse or technologist puts a thin tube into a vein in your arm or hand with a small needle, the same as for a blood test.
Lying down. You lie on a padded table. A frame goes around your head. It looks like a cage or a helmet, and it is what picks up the pictures.
Ear protection. You are given earplugs or headphones. You need them.
Into the scanner. The table slides you into a tube that is open at both ends. You are alone in the room, but the staff watch you the whole time. They can talk to you, you can talk back, and you are given a button to press.
The dye. If you are having it, it goes in through the tube in your arm part way through. Sometimes a machine does it. Sometimes someone comes in and slides the table out to do it by hand.
Afterwards. The staff may check the pictures before you get dressed, in case they need more. Then you can go, and you can eat, drink and get on with your day as normal.

Unless you are told otherwise, take your usual medicines that day. Rules about eating and drinking before a scan are different at different places, so go by what your center tells you.

How long does it take?

Most MRI scans take somewhere between 15 and 45 minutes. Some take an hour or more. If you are having dye, it takes longer, because two sets of pictures are taken: one before the dye and one after.

The person running the scan can tell you before you start how long yours should take.

You do not have to lie perfectly still for the whole hour. You have to be still while each set of pictures is being taken. Between sets you can often move a little. Ask about that before you go in. Knowing you get breaks makes the whole thing easier.

What does it feel like?

Loud, mostly. The scanner bangs, knocks and buzzes while it works. The noise is normal and it does not mean anything is wrong. That is what the earplugs are for.

The scan itself does not hurt. You lie on your back on a padded table and stay still. Some people find it boring. Some people find it long. Neither is a sign that anything has gone wrong.

If you are having dye, the needle for the line in your arm feels like having blood taken.

If small spaces frighten you

Say so, early. This is a normal thing to be frightened of, and there is a lot your center can do about it. What there is not, is any need to get through it on your own.

You can ask your doctor for a mild calming medicine before the scan. Ask in advance, not on the day. If you take one, arrange a ride home, and check with the staff about driving.
Some centers let a person you know come into the room with you, or let you bring something of your own in. It helps more than people expect.
Ask about music. You are given headphones anyway, so it is worth asking whether they can play something through them.
Some centers have more than one machine, and one of them may be less closed in. Ask what they have. Machines differ in what they can show, so let the center tell you which of theirs suits your scan.
Knowing exactly what will happen helps. That is most of what this page is for. Ask the staff to walk you through it first.

When people are prepared and know what to expect, it is almost always possible to get the scan finished. Tell them you are worried. They have seen it many times and they would much rather know.

The dye: what people ask about it

The dye is a liquid called contrast dye: A liquid put into a vein before some scans. It makes certain tissues stand out, which helps show where a tumor is. It does not always show the whole of it. See the glossary. It goes into a vein and makes some tissue stand out, which helps show a tumor more clearly.

Is it the same as the dye for a CT scan? No. It has no iodine in it, and it only rarely causes a reaction of any kind. Your CT scan covers the other one, which has different rules.

Who needs to speak up first? Tell the staff before the scan if you have kidney disease, kidney failure, a kidney transplant or liver disease, or if you have ever reacted to this dye before.

Does it stay in my body? Small amounts can stay after many scans. There are no known health effects from this. It is most likely in people who have a lot of scans over their lifetime, which includes people with a brain tumor. It is a fair thing to ask your team about, and it is worth asking once so it stops sitting at the back of your mind.

What if I am pregnant, or might be? Tell them at the safety form. There is no known risk to a baby from the scan itself, and MRI is usually safer than an x-ray or a CT scan. Most centers avoid the dye during pregnancy to be careful.

What if I am breastfeeding? Tell the clinic when you book. Doctors take it as safe to carry on feeding after the dye. Some parents choose to pump some milk beforehand and use it for the next day instead. Either choice is fine, and the clinic can talk it through with you.

Metal, implants and your device card

If you have a device fitted, bring its card. That one thing solves most of it.

Many newer devices are fine in an MRI, including some pacemakers, heart defibrillators, nerve stimulators, cochlear implants and medicine pumps. What the staff need is the exact make and model, which is what the card gives them. Without it they may have to be cautious for no reason. If you have a shunt, Shunts and hydrocephalus says what to tell them.

A few things do stop a scan. Some clips used on blood vessels in the brain are made of metal that a magnet pulls on, so the team checks which kind you have. Metal near the eye has to be checked first too, and that is more likely if you have worked with metal.

Some other things to know:

Clothes with metal threads in them, including some sports clothes, can heat up and burn your skin. A gown avoids the whole problem, which is why you are usually given one.
Tattoos can sometimes sting or feel hot. Tell the staff if you have them.
Metal in your body does not always stop the scan, but it can smudge the pictures. If the staff know it is there, they can work around it.

If a center tells you it cannot scan you, ask why, and ask what else would show the same thing. It is also fair to ask another center. Some have machines or staff that can handle devices others cannot.

Why am I having another scan?

Two scans catch almost everyone out. Both are normal, and neither means something has gone wrong.

This one is a map, not a repeat.

A scan can be done before an operation to map exactly where the tumor sits, which matters most when it is deep in the brain. Your team may call it the neuronavigation: A map of your head that a surgeon follows during surgery. It is built from a scan taken beforehand. Stickers on your scalp, or the shape of your face, line it up with you. See the glossary. For some procedures small markers are stuck on your scalp first, or the shape of your own face is used instead, so the pictures can be lined up with your real head in the room.

So being sent for another MRI days after the last one is not a sign that the first was wrong or that something has changed. It is the surgeon getting the map they work from.

The scan just after surgery

This one is usually done within a day or two, and it is booked that soon on purpose.

It does two jobs. It shows how much of the tumor was taken out. It also becomes the picture that every later scan gets compared with, which is why it matters so much.

The reason for the rush is simple. Healing itself shows up on a scan, and the longer you wait, the more of it there is to see and the harder it is to tell healing from tumor. Getting the scan early gives your team a clean picture to measure everything else against.

The scans that come later, once treatment is over, are asked for a different reason again. Follow-up scans, and what the results mean covers those, and what the words on the report mean.

Who reads my scan, and how do I get the result?

How long it takes depends on where you are, so ask before you leave. What follows is who does what, so you know what the wait is made of.

A radiologist: A doctor trained to read scans and write down what they show. The report goes to the doctor who asked for the scan, who then tells you. One who specializes in the brain and spine is called a neuroradiologist. See the glossary reads the pictures. That is a doctor trained to read scans. They send a signed report to the doctor who ordered it, and that doctor tells you.

For a brain tumor, your scan may also go to a tumor board: A meeting where specialists talk through one person's case together: the surgeon, the cancer doctor, the lab, and whoever read the scans. You are not there. What they decide is advice your own doctor goes through with you. See the glossary.

A tumor board is a meeting where specialists look at one person's case together: surgeons, cancer doctors, the lab, and the people who read scans. It tends to happen when a case is complicated or something is hard to read.

You do not go to the meeting. Afterwards, the doctor who knows you best explains what was said.

What they decide is advice, not an order. The choice is still yours. Because you are not in the room, tell your team what matters to you before it happens, so it is taken into account.

The wait is the part most people find hardest. You can shorten the not-knowing a little by asking, before you leave the scan: when should the result be ready, and who is going to call me?

What to ask your team

Is this scan with dye, without, or both, and why?
I have this device. Here is the card. Is it safe, and does anything need changing first?
I get very anxious in small spaces. What can you offer me?
If I have a calming medicine, can I drive myself home?
How long will the scan take, and how long do I need to stay still at a time?
Can someone come in the room with me?
When will the result be ready, and who will call me?
Will my scan go to a tumor board before I hear anything?
Can I get a copy of my pictures, for my own records or for a second opinion?

Where to go next

Just diagnosed? Start here if this is all new.
Your CT scan for the fast scan that usually came first, and the one that does not use a magnet.
The extra scans before treatment if your team has mentioned adding sequences to plan an operation or radiation.
How tissue is taken for the step after this one, when a scan has gone as far as a scan can go.
Waiting for your pathology results if tissue has been taken and you are waiting to hear what it is.
Your pathology report, part by part once that report is in your hands.
Getting ready for surgery if this scan is the one your surgeon will navigate by, and the operation is being planned.
Follow-up scans, and what the results mean for the scans that carry on after treatment, and the words used to describe change.
Brain tumor types to read about your own diagnosis.
What to do when someone has a seizure, which is worth reading before you need it.
The glossary for any word on your report you do not recognize.

This is not medical advice. It explains research in plain words. Your care team knows your case. Talk with them before you make any decision about your treatment.

Last reviewed: August 31, 2026

Sources for this page: