Tests That Help Evaluate a Brain Tumor
Your doctor will order more tests if he or she thinks you have a brain tumor. Here are some of the tests.
Magnetic Resonance Imaging (MRI)
An MRI scanner uses magnets and strong radio waves to make pi ctures of the brain. MRIs are very useful in diagnosing brain tumors because they allow your doctor to “see through” your skull. This results in clearer pictures of the brain. A technician might inject a special dye into your vein to make it easier to see the difference between a tumor and normal brain tissue. An MRI can show slices of the brain from many different angles. It can show smaller details better than other scans. An MRI is especially helpful in finding cancer in the back part of the brain called the posterior fossa. It is also better at finding cancer within the spinal cord.
Computed Tomography (CT) Scan
A CT scan is a type of X-ray that provides detailed pictures of the brain. Many images of the brain are taken as the X-ray scanner moves around your head. A computer combines these many images into a useful picture. Sometimes a technician injects a special dye into a vein before the CT scan to enhance the difference between normal and abnormal tissue. CT scans can also show these problems that require immediate attention.
Positron-Emission Topography (PET) Scan
In a PET scan, a technician injects a small amount of radioactive material into your vein. Fast-growing tissue such as the tumor absorbs this dye and can be seen by using a special type of scanner. The radioactive material used in this test is not dangerous. It will leave your body in about 6 hours. PET scans can help your doctor tell the difference between dead tissue and an actively growing tumor.
Angiogram
An angiogram may also be called arteriogram or venogram, depending on which type of blood vessel is accessed. It’s a series of X-rays taken after a technician injects a special dye into one of your blood vessels. A technician also inserts a catheter into one of your large blood vessels, usually in your groin, and then positions it with the help of an X-ray. After injection, the dye flows through the blood vessels in your brain and can be seen on X-rays. These X-rays show the tumor and the blood vessels that lead to it.
Magnetic Resonance Angiography (MRA)
This is a special type of MRI. An MRA is a new, less invasive alternative to an angiogram. But certain types of cancer cannot be seen with this technique.
Myelogram
A myelogram is an X-ray of the spine. A technician injects special dye into your cerebrospinal fluid in the spine to help make tumors more visible. This test is rarely done because MRIs offer more information without injecting dye into the spine.
Skull X-Ray
Certain types of tumors can leave calcium deposits. A skull X-ray is very good at seeing these. Skull X-rays will also show changes to the structure of the skull caused by tumors.
Other Tests
You may need formal testing of your vision or hearing. Your doctor may want to do an electroencephalogram (EEG), which checks your brain waves, to rule out invisible seizures. If these tests suggest that a tumor might be present, a neurosurgeon will take a biopsy. This is the only way to know for sure if a tumor is benign or malignant.
For a brain tumor biopsy, a doctor takes out as much of the tumor as possible through a bone “window” made in your skull. A pathologist examines this sample under a microscope to see if it is cancer.
Another type of biopsy is the stereotactic biopsy. For this biopsy, the neurosurgeon removes a small piece of the tumor with a needle. The needle is carefully guided and placed in the tumor with the help of an imaging test, such as an MRI or CT scan.