Tests for Brain Tumors in Adults

MRI uses strong magnets and radio waves to make detailed pictures of the inside of your body. This is the best test for looking for brain and spinal cord tumors, and it’s often the first one done.

Most often, 2 scans are done. Before the second scan, a contrast material called gadolinium is injected into a vein to help see tumors better.

Special types of MRI can be useful in some situations:

Magnetic resonance spectroscopy (MRS) measures biochemical changes in an area of the brain and displays them in graph-like results called spectra. It’s done as part of an MRI, so regular MRI pictures are taken at the same time.

MRS can help determine:

• The type of tumor or how quickly it is likely to grow, by comparing the results for a tumor to normal brain tissue
• Whether an area that still looks abnormal after treatment is more likely to be remaining tumor or scar tissue

Magnetic resonance perfusion (also called MR perfusion or perfusion MRI) shows the amount of blood going through different parts of the brain, using a contrast dye injected quickly into a vein. Tumors often have a bigger blood supply than normal areas of the brain, and a faster-growing tumor often needs more blood.

MR perfusion can help determine:

• The best place to take a biopsy
• Whether an area that still looks abnormal after treatment is more likely to be remaining tumor or scar tissue

Functional MRI (fMRI) looks for tiny blood flow changes in an active part of the brain. It’s like a standard MRI, except that you will be asked to do specific tasks (such as answering simple questions or moving your fingers) while the scans are being done.

fMRI can help determine which part of the brain handles a function such as speech, thought, sensation, or movement so doctors can avoid these areas when planning surgery or radiation therapy

Diffusion tensor imaging (DTI) or tractography shows where the major pathways (tracts) of white matter (nerve fibers) are in the brain so surgeons can avoid these areas when removing tumors.

Magnetic resonance angiography (MRA) and magnetic resonance venography (MRV) look at the blood vessels (arteries or veins) in the brain. This can sometimes be useful before surgery to help plan an operation.

A CT scan uses x-rays to make detailed cross-sectional images of your brain and spinal cord (or other parts of the body).

CT scans aren’t quite as good as MRI scans for looking at brain or spinal cord tumors, so they aren’t used as often. But they may be used if MRI isn’t an option for some reason, or if a scan is needed right away. CT scans can also show greater detail of the bone structures near the tumor than an MRI.

You may get an injection of a contrast dye through an IV (intravenous) line before part of the scan. This helps better outline any tumors that are present.

CT angiography (CTA): For this test, you are injected with a contrast material through an IV line while you are in the CT scanner. The scan creates detailed images of the blood vessels in the brain, which can help doctors plan surgery. CT angiography can provide better details of the blood vessels in and around a tumor than MR angiography in some cases.

For a PET scan, you are injected with a slightly radioactive substance that collects mainly in tumor cells. A special camera is then used to create a picture of areas of radioactivity in the body.

Unlike CT or MRI scans, which show what the brain looks like, a PET scan shows how the brain is working. It highlights areas that are more active or using more energy. This can help doctors see whether an area is behaving like a tumor, even if it doesn’t look very different on other scans. The pictures are not as detailed as a CT or MRI scan, but they can help tell whether abnormal areas seen on those tests are likely to be tumors.

This test is more likely to be helpful for fast-growing (high-grade) tumors than for slower-growing ones.

A PET scan can also be useful after treatment to help determine whether an area that still looks abnormal on an MRI is more likely to be remaining tumor or scar tissue. Tumor usually shows up on a PET scan, while scar tissue does not.

Many centers now use machines that can do both a PET scan and a more detailed scan at the same time (PET/MRI or PET/CT).

A chest x-ray might be done to look for tumors in the lungs if a tumor is found in the brain. This is because in adults, most tumors in the brain are actually cancers that started in another organ (most often the lung) and then spread to the brain.

A stereotactic (needle) biopsy may be used if, based on imaging tests, a biopsy sample is needed but surgery to remove the tumor might be too risky (such as with some tumors in vital areas, those deep within the brain, or other tumors that probably can’t be removed safely with surgery).

The biopsy may be done while you’re asleep under general anesthesia or while awake. If you need to be awake for the procedure, the neurosurgeon will inject the area with a local anesthetic to numb the skin. (The skull and brain do not feel pain.)

The biopsy itself can be done in 2 main ways:

• The most common approach is to get an MRI or CT and then use either markers (each about the size of a nickel) placed on different parts of the scalp, or facial and scalp contours, to create a map of the inside of the head. The neurosurgeon then makes an incision (cut) in the scalp and drills a small hole in the skull. Using an image-guidance system, they insert a hollow needle into the tumor to remove small samples of tissue.
• In an approach that’s being used less often, a rigid frame is attached to the head. An MRI or CT scan is often used along with the frame to help the neurosurgeon guide a hollow needle into the tumor. This also requires an incision in the scalp and a small hole in the skull.

The removed tissue (biopsy sample) is sent to a pathologist (a doctor specializing in diagnosis of diseases by lab tests) or neuropathologist (a pathologist who specializes in nervous system diseases).

The pathologist looks at the biopsy sample under a microscope (and might do other lab tests) to determine what type of tumor it is. A preliminary diagnosis might be available the same day, although it often takes at least a few days to get a final diagnosis.

If imaging tests show the tumor can likely be treated with surgery, the neurosurgeon may do a craniotomy to remove the tumor instead of a needle biopsy. If removing the whole tumor would likely damage nearby important structures, then the tumor might be debulked to remove most (but not all) of it.

For a preliminary diagnosis, small samples of the tumor are looked at right away by the pathologist while the patient is still in the operating room. This can help guide treatment, including whether further surgery should be done at that time. A final diagnosis is made within a few days in most cases.

You can read more about the kinds of tests done on biopsy or tissue samples in How Biopsy and Cytology Samples Are Tested for Cancer.