The extra scans before treatment, and what each one is for

Nobody is offered a functional MRI on its own. You are told your team wants to add some sequences. What each of the extra scans answers, which one gives you a job to do, and why a map is not the same as a verdict.

The short version

Before an operation or radiation, your team may add more scans. Most of them are extra minutes in the same MRI machine, each one answering one specific question about where things sit. One is different from all the others: in a functional MRI you have a job to do while you are in there, and you cannot fail it. What these scans make is a map, not a verdict. They help your team plan around the parts of your brain you would notice losing, and for a critical decision your doctor may ask for more tests to confirm what one of them shows.

What are these extra scans?

Mostly they are not separate appointments at all. They are extra sets of pictures taken during an MRI you were having anyway. The room is the same, the machine is the same, the noise is the same, and the dye is the same.

What changes is the question being asked.

Your MRI scan is the whole of that appointment, from the safety form to the trip home, and everything on it still holds when a sequence is added. So this page does not repeat it.

Here is what your team may add, and what each one answers:

• Functional MRI: which part of your brain does which job. The one where you have something to do.
• DTI: where the wiring runs between those parts.
• MR spectroscopy: what the tissue is made of, chemically.
• Perfusion: how much blood is going through it.
• PET: what the tissue is doing. This one is its own appointment.
• Pictures of the blood vessels: where the arteries and veins run before anyone opens the skull.

If radiation is your treatment rather than an operation, the planning scan you meet is a different thing again: a CT taken in a mask made for you, at a visit of its own. Radiation therapy walks through that one, and none of the scans below replace it.

Why am I having one?

Because somebody has a specific question, and an ordinary MRI does not answer it.

These are not ordered automatically. A surgeon or a radiation oncologistradiation oncologist: The doctor in charge of radiation treatment. They decide which area is treated, and how the treatment is split up. See the glossary asks for the one that answers the thing they need to know:

• Which part of the brain handles speech, thought, sensation or movement here, so that the plan can steer around it.
• Where the main nerve pathways run, so that an operation does not cut through one.
• How much blood is going through the tissue, which is one of the things that suggests how fast it is growing.
• What the tissue is made of, which can help suggest what kind of tumor it is.

The question worth asking is a short one: what is this scan for, and would the answer change the plan? Your team should be able to answer it directly, and it turns another appointment into a step you can see the point of.

What happens on the day

For everything except a PET, this is the answer:

1. It is usually the same appointment. The extra pictures are taken during your MRI, often without the day looking any different to you.
2. Same table, same frame, same noise. You lie on your back with a frame around your head, exactly as before.
3. A line in your arm, if the scan needs dye. A perfusion scan does. Others do not.
4. You hold still. For most of these there is nothing for you to do at all. The scanner does the work and you lie there.
5. Except one. In a functional MRI you have tasks to do, and there is a whole section about that below.

A PET scan is the exception to all of it. It happens in a different department, on a different day, and its own section walks through it.

How long does it take?

For the MRI add-ons, think in extra minutes rather than another appointment. How many depends on how many sequences your team asked for.

The person running the scanner can tell you before you go in how long yours should take, and it is worth asking, because the answer is often shorter than people brace for.

A PET is longer, and most of the extra time is waiting rather than scanning. See the PET section for the shape of that day.

What does it feel like?

Like more of the same. The main cost is time spent lying still.

If lying still is the part you find hard, that is worth saying before you go in rather than after. Your MRI scan has what your center can offer, and all of it applies here.

The scan where you have a job: functional MRI

This is the one that is unlike the others, because it is the only one where what you do changes what the scan can show.

What it is. A functional MRI measures the small changes in blood flow that happen when a part of your brain is working. Doing a task makes a part of your brain work. The scan watches where the blood goes while you do it.

What it is for. It helps your team work out which part of your brain handles a job such as speech, thought, sensation or movement, so they can plan around those areas. That is the only use it is approved for in the United States: planning an operation.

What you actually do. Simple things, one at a time, while you lie in the scanner:

• Tapping a thumb and finger together, on one hand or the other.
• Moving a foot.
• Reading words.
• Reading a word backwards.
• Thinking of words without saying them out loud.
• Naming objects you are shown.

Which tasks you get depends on where your tumor is. A tumor near the part that runs your hand gets a hand task. A tumor near the speech areas gets word tasks. You may also be asked to hold your breath for a few seconds at a time. That one is not testing your brain. It is checking the blood vessels, and the next part explains why that matters.

You cannot fail this. Of everything on this page, it is the part to carry into the room with you. The scan needs you to be able to do the tasks, so if one is too hard, or you are having trouble doing it, tell the person running it. They can give you different tasks or easier questions. That is not you failing the test. In one study of people having this scan before surgery, swapping to simpler tasks gave more reliable results, not worse ones. Saying "I cannot do that one" makes the scan better.

Holding still matters more here than usual. This scan is especially sensitive to head movement, and the radiology societies' own patient guidance names who finds that hardest: anyone who is anxious, confused or in a lot of pain. If that is you, say so beforehand. It is a reason to prepare rather than a reason to be brave.

Keep your coffee normal. This is an odd instruction and a real one. If you drink coffee every morning, do not skip it on the day. If you hardly ever drink it, do not have one that morning. Caffeine changes blood flow, and blood flow is what this scan measures.

The limit, and it is a real one

A tumor can break the normal link between a part of the brain working and the blood flowing to it. Doctors call that neurovascular uncoupling.

Here is why it matters to you. The scan does not watch your brain working. It watches the blood. So near a tumor, a part of your brain that is working perfectly well can fail to light up, and a quiet spot on the map looks like a spot that is safe to operate on. That is the wrong way round to be wrong.

The breath-holding runs are one of the ways a team checks for this. Holding your breath changes the blood flow everywhere without asking your brain to do anything, so it shows whether the blood vessels in that area can still respond at all.

There is also less experience with this scan than with most other kinds of MRI. So your doctor may recommend more tests to confirm what a functional MRI shows, when there is a critical decision to make such as planning brain surgery.

For a tumor near a speech or movement area, the test that confirms it is often done in the operating room rather than beforehand. In an awake craniotomy the surgeon checks the same question directly, on the day, one small spot at a time.

The map of the wiring: DTI

What it is. The working parts of your brain are joined to each other by bundles of fibers that carry signals between them. Think of them as cables. A DTI scan shows where the major ones run. You may also hear it called tractography.

What it is for. So a surgeon can see the cables and avoid them while taking a tumor out. It can also show what the tumor has done to them: pushed a bundle aside, grown into it, or broken it. Those are different problems with different answers, and surgeons use the difference to plan both the route in and how much they can safely take.

What you do. Nothing. No tasks, no extra injection. It is more minutes on the same table.

The chemistry graph: MR spectroscopy

What it is. Every other scan on this page makes a picture. This one makes a graph. It measures the chemicals in a patch of brain and draws them as a set of peaks.

What the peaks mean. Healthy brain tissue has a normal mix. Tumor tissue usually does not, and the pattern of what is high and what is low is the useful part:

• Choline is part of the wall around a cell. More of it means cells are being made and replaced faster than normal.
• NAA is found in healthy nerve cells, so less of it means nerve cells have been damaged or crowded out.
• Creatine is used as a steady reference to measure the others against.
• Lactate is not seen in a normal adult brain at all. It turns up where tissue is short of oxygen.

What it is for. It can help suggest what kind of tumor something is. It does not name it. Only a piece of the tumor itself, looked at in a lab, can do that. The gene results that go with the name come from that same piece, not from this graph. The words on your gene results takes them one at a time.

What you do. Nothing extra. More minutes in the same machine.

The blood supply scan: perfusion

What it is. A scan that shows how much blood is going through different parts of the brain.

What it is for. Tumors often have a bigger blood supply than normal areas of the brain, and a faster-growing tumor often needs more blood. That makes the blood supply a useful thing to know. It can also help decide the best place to take a piece from, if tissue is being taken. How tissue is taken covers that step.

What you do. This is the one that needs dye. It goes into the line in your arm quickly, during the scan, and you are asked to stay very still while that set of pictures is taken.

Perfusion is used after treatment as well, for a different question entirely. Follow-up scans, and what the results mean is where that belongs, and it is not the same conversation as this one.

The tracer scan: PET

What it is. You are injected with a slightly radioactive substance that collects mainly in tumor cells. The scanner then finds where it has gone. Most of the other scans here show what tissue looks like. This one shows what it is doing.

What it is for. Before treatment, the job it does here is helping choose where to take a piece from. The spot taking up the most tracer is the one worth sampling. It is more likely to help with fast-growing tumors than with slow-growing ones.

It is also used after treatment, to help work out whether an area that still looks odd on an MRI is more likely to be tumor or scar tissue. That is a whole question of its own, and it does not have a clean yes or no in it. Follow-up scans, and what the results mean is the page that goes through what the fancier scans can and cannot settle.

There is more than one kind of tracer, and it is worth asking which. The usual one is a form of sugar. In the brain that causes a problem, because normal brain tissue uses a lot of sugar anyway, so a tumor can be hard to pick out against everything around it. There is another kind, made from an amino acid instead, which normal brain takes up much less of. Ask whether the kind your team has in mind is done where you are being treated, or whether you would be going elsewhere for it.

The day is different from the others. This is its own appointment:

1. You are usually asked not to eat for several hours beforehand, and to drink water only.
2. A small needle goes into a vein in your arm. You feel a pin prick.
3. Then you wait, and this is the part nobody expects. The tracer needs roughly 30 to 60 minutes to collect where it is going. You spend that time sitting quietly, asked not to move about or talk, because moving a muscle sends the tracer to that muscle.
4. The scan itself takes about half an hour.
5. Afterward you can get on with your day. The tracer leaves your body over hours to days, and drinking water helps it along.

Apart from the injection, none of it hurts.

If you are breastfeeding, raise it when you book. The advice is to ask the radiology department or your own doctor how to go about it, and it may help to pump some milk beforehand and keep it for use until the tracer and any CT dye have left your body. Tell them if there is any chance you are pregnant, too.

Pictures of the blood vessels

Short, because there is not much to it from where you are lying.

A surgeon may want to know where the arteries and veins run before opening the skull. There are MRI versions of that picture, and there is a CT version, which in some cases shows the vessels in and around a tumor better than the MRI version does. Your CT scan covers what a CT is like.

You do nothing during these. They are more pictures taken while you lie there.

What is hard about these, and what helps

Three things, and each has something you can do about it.

More time lying still. That is the real cost of most of these. Ask the person running the scan how long yours will take and whether there are breaks between sets of pictures. There usually are, and knowing that changes the whole hour.

Another injection. It is the same kind of line that goes in for an MRI with dye. If your veins are hard to find, say so at the start rather than after the third attempt, and ask whether the line can be put in by somebody who does the difficult ones.

Being asked to perform. The functional MRI is the one that worries people, because it feels like a test with a pass mark. It is not one. Ask to be told the tasks in advance so you can think about them at home, and tell them on the day if one is too hard. Both of those make the scan better.

And if being sent for more scans is itself the frightening part, follow-up scans has the section about that, and it holds here too.

What to sort out before the day

• Ask what the scan is called and what question it answers. You are allowed to write the name down and look it up.
• Ask whether you have to do anything during it. For most of them the answer is no, and knowing that is worth the question on its own.
• Ask whether it needs dye or a tracer, and whether that changes anything about eating, drinking or driving.
• Ask whether it is done where you are being treated, or whether you would be going somewhere else for it.
• Tell them about any device or metal in your body. These are MRI scans, so the same rules apply. Your MRI scan covers the device card, and bringing it solves most of it.
• Keep your caffeine normal on the day, if a functional MRI is one of them.
• For a PET, check the eating and drinking rules, because that one usually has some.
• If small spaces are hard for you, say so in advance rather than on the day. Your MRI scan lists what your center can offer.

Who reads it, and how do I get the result?

How long it takes depends on where you are, so ask before you leave.

A functional MRI is read by a radiologistradiologist: 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, a neurologist or a neuropsychologistneuropsychologist: A psychologist who looks at how a brain problem changes thinking. They read the tests of memory, attention and language. Then they write the report that says what would help. See the glossary trained to read them, which is a wider set of people than usual. The rest of the scans on this page are read by a radiologist, as your first MRI was. Your MRI scan has more on who does what.

The thing worth asking about here is different from a normal scan. These scans are asked in order to make a plan. So the answer may reach you as part of a conversation about what is going to happen, rather than as a result on its own. Ask which it will be: do I hear about this separately, or at the appointment where we decide.

What to ask your team

• What question is this scan answering, and would the answer change the plan?
• Do I have to do anything during it, and can I know the tasks beforehand?
• Does it need dye, or a tracer, or another needle?
• Is it done here, or would I be going somewhere else?
• How long will I be in there, and are there breaks?
• I find lying still hard. What can you offer me?
• For a functional MRI: what happens if I cannot do one of the tasks?
• How much does the plan rest on this scan, and is anything checked again during the operation?
• Do I hear the result separately, or at the planning appointment?
• Can I take away a disc or a link to these images?

Where to go next

• Your MRI scan for the appointment itself, all of which still applies to every scan on this page.
• Your CT scan for the fast scan that usually came first.
• An awake craniotomy if your team has raised being awake for part of the operation, which is where the same question gets checked directly.
• Brain surgery, step by step for the operation these scans are planning.
• Radiation therapy for its own planning visit, which is a different appointment from these.
• How tissue is taken for the step that gives the tumor a name.
• Follow-up scans, and what the results mean for what these same scans are used for after treatment.
• The glossary for any word here you want in one line.