Pediatric Brain Tumor Foundation
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Diagnostic Tools and Imaging

Can a brain tumor be diagnosed by its symptoms alone?
Will my child need to be under anesthesia for the MRI?
What happens during the MRI?
Can a CT scan cause cancer?
Will my child need a PET scan?
What’s the difference between a “resection” and a “biopsy”?
How long will my child require scans following treatment?

Can a brain tumor be diagnosed by its symptoms alone?
No, the symptoms of brain tumor frequently mimic disorders that are much more common. Confirmation of a tumor is made after a scan, such as computerized tomography (CT), which is usually followed by magnetic resonance imaging (MRI).

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Will my child need to be under anesthesia for the MRI?
Patients need to remain completely still during an MRI, and the procedure may last up to an hour. Therefore, anesthesia may be required for children younger than 8 and older ones who are anxious. This means that your child will not be allowed to eat for several hours before the MRI and may be drowsy afterwards.

Video goggles and headphones, as well as your presence (if the hospital allows it), may help calm children who are old enough to have the MRI without anesthesia.

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What happens during the MRI?
Before the test, a contrast material may be injected into your child’s vein. This will help doctors identify fine detail of a tumor and any abnormalities of the brain. Your child will lie on a mechanical table, which is moved into a large structure with a doughnut-shaped opening. An “open MRI” means the top and sides are open, while a “closed MRI” will feel like going into a tunnel.

MRIs do not use ionizing radiation, which is a carcinogen. Because of this they are safe. They provide very intricate images of the brain and soft tissue, and are the most sensitive tool for detecting brain abnormalities.

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Can a CT scan cause cancer?
Unlike MRIs, a CT scan does use ionizing radiation, which with repeated exposure can increase the chance of developing cancer many years later. For this reason doctors are conservative in recommending CTs for children.

When used appropriately, CT scans can be very useful. CT is a much quicker than an MRI, making it lifesaving in its ability to identify neurological emergencies. Consequently, it is often the first type of scan done when your child is first being diagnosed with a brain tumor. CTs can more accurately detect calcium deposits, a feature of some tumors, and can provide more detailed pictures of the outer layer of the skull than other imaging techniques.

In general, MRI scans are used instead of CT to follow the progress of brain tumors over time and after treatment.

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Will my child need a PET scan?
A positron emission tomography (PET) scan is used less frequently in diagnosing CNS tumors, but can provide information about the aggressiveness of disease and help determine the difference between scar tissue and recurring tumor. PET scans are not often used for newly diagnosed brain tumors.

A PET scan provides a picture of the brain’s metabolic activity, rather than its structure, by measuring the rate at which a tumor absorbs glucose (sugar). Your child will need to skip eating for four to six hours before a radioactive glucose tracer is injected through a vein. This tracer is needed so the radiologist can track how it is absorbed by the body.

After the injection, you child must wait for about 30 minutes while the tracer circulates throughout the body. Next your child will lie on a table that slides into a large tunnel-shaped scanner, then remain still for up to 30 minutes.

The PET detects signals from the tracer and changes them into 3-D pictures for the doctor to read. The amount of radiation used in a PET is about the same as for a CT scan. As is the case for MRI scans, younger children and those who are anxious may need to be under anesthesia.

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What’s the difference between a ‘resection’ and a ‘biopsy’?
If a tumor occurs in an area where it’s difficult to resect (surgically remove), a neurosurgeon may perform a biopsy, or limited surgery, so that a pathologist can make the diagnosis by examining a small piece of the tumor tissue under a microscope.

Biopsies can be either “open” or “closed” depending on the surgical technique used. In a closed biopsy,  also known as a stereotactic or needle biopsy, a small hole is drilled into the skill and a tissue sample is removed via a narrow hollow needle. An open biopsy is done during surgery. The pathologist’s report will help your child’s medical team devise the best treatment plan.

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How long will my child require scans after treatment?
It depends on the tumor type and clinical scenario. Often, routine follow-up imaging MRI scans are performed every three or four months for the first year after treatment is completed, and then less frequently over several years unless there is clinical concern for recurrence.

Content reviewed September 2013. To follow up on any diagnostic tools and imaging questions, please email us or call 800-253-6530.

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