Doctors use many tests to diagnose a brain tumor, determine the type of brain tumor, and learn if it has metastasized (spread). A biopsy is usually required to diagnose the type of brain tumor.
In addition to asking for a detailed medical history and doing a physical examination, your doctor may recommend the following tests:
A CT scan produces a series of detailed, two-dimensional images of the brain created by a computer linked to an x-ray machine. The patient lies on a sliding table that's guided into what looks like a small tunnel where the images are taken. A special dye may be injected into a patient's vein to provide better detail. A CT scan is painless and generally takes less than 10 minutes.
MRI is a procedure that uses a magnet, radio waves and a computer to produce detailed pictures of the brain and spinal cord.
The Northwestern Brain Tumor Institute offers specialized applications of MRI imaging, including:
- MRI Spectroscopy - MRI Spectroscopy combines MR imaging and chemical analysis of the brain's chemistry. This procedure can be used to grade tumors and assist the surgeon in localizing the optimal place for a biopsy if a tumor cannot be removed.
- MR perfusion - MR perfusion assesses the patient's blood flow and can assist in grading tumors and identifying the best place for a biopsy.
- Functional MRI - Functional MRI is used to determine what parts of the brain "light up" when functions such as speech or recognition are engaged, thereby minimizing the chance of injury to these areas.
- Diffusion Tensor Imaging - Diffusion Tensor Imaging provides detailed information about the motor or visual fibers in the brain, again helping to minimize injury when tumors are near these areas.
PET is a procedure in which a small amount of radioactive glucose (sugar) is injected into a vein, and a scanner is used to make detailed, computerized pictures of areas inside the body where the glucose is used.
Your doctor may also ask for other tests, including:
Dye injected into the bloodstream during an angiogram flows into the blood vessels in the brain to make them show up on an x-ray. If a tumor is present, the doctor may be able to see it on the x-ray.
Removal of tissue to look for tumor cells is called a biopsy. The sample removed from the biopsy is analyzed by a pathologist (a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease). A biopsy can show cancer, tissue changes that may lead to cancer, and other conditions, and is the only definitive way a brain cancer diagnosis can be made.
A cerebral angiogram, also called a cerebral arteriogram, is an x-ray, or series of x-rays, of the head that shows the arteries in the brain. X-rays are taken after a special dye is injected into the main arteries of the patient's head.
Because some specific types of brain tumors can spread to the spinal fluid, other parts of the brain, or the spinal cord, the doctor may order a myelogram to look for metastases. A myelogram uses a dye injected into the cerebrospinal fluid CSF that surrounds the spinal cord. The dye shows up on x-ray and can outline the spinal cord to help the doctor look for tumors.
Some types of brain tumors cause calcium deposits in the brain or changes in the bones of the skull. With an x-ray, your doctor can check for these changes.
Your doctor may remove a sample of cerebrospinal fluid (the fluid that fills the spaces in and around the brain and spinal cord). This procedure is performed with local anesthesia. The doctor uses a long, thin needle to remove fluid from the spinal column. A spinal tap takes about 30 minutes. The patient must lie flat for several hours afterward to keep from getting a headache. A laboratory checks the fluid for cancer cells or other signs of problems.