Brain Scans (Neuro-Imaging Studies)

A brain scan is a type of diagnostic test that takes pictures of the brain and/or spinal cord. Like an X-ray can see inside the body to diagnose a broken bone, a brain scan can see a tumor inside the skull. The two most common scans for diagnosing a brain tumor are magnetic resonance imaging (MRI) and computed tomography (known as a CT or CAT scan). A CT is often used to detect the presence of a tumor, and an MRI is used to gather more detailed information about the tumor’s size, location, and possible type (a biopsy is needed to confirm tumor type).

Brain scans are non-invasive. A noninvasive procedure is one that does not involve cutting into the body or removing tissue, and is generally painless. For some, the most challenging part of a scan is having to sit or lie still for a long time.

During a scan, your doctor may use a special dye, called contrast, to make areas of the brain easier to see. Contrast material is usually injected into a vein before the scan starts. Prior to the scan, you will be provided with information, including any details and instructions about the contrast agent (if prescribed), what to wear, and what to bring along. The doctor will determine if you need a blood test to ensure your kidneys are safe to receive contrast. Let the doctor know if you have any allergies.

Computed Tomography (CT)

CT scans are commonly used as screening scans, and are preferred for looking at bones or the presence of blood or abnormal brain tissue  They are safe overall but do expose patients to a small amount of radiation. This scan combines high-speed X-ray technology with a computer. The CT scanner is a large donut-shaped piece of equipment.  The patient lies on a table that slides into an opening in the CT machine. The CT scanner circles the head, taking X-rays from different angles. A computer then combines these X-ray images into a cross-sectional image of the brain (sometimes called a “slice”). A contrast dye may be injected to help the tumor appear more clearly in the CT scan results. These images help the doctor determine the presence and location of a tumor.

Magnetic Resonance Imaging (MRI)*

The MRI scanner is a tunnel-shaped piece of equipment that uses magnets and radio waves to generate two-dimensional or three-dimensional pictures of the brain tissue. These images are more detailed than those of a CT for assessing the presence of a brain tumor. The patient lies on a table that slides into the scanner, where a magnetic field surrounds the head. Prior to the scan, a contrast dye (typically gadolinium) is injected into the body. This contrast agent helps some tumors appear more clearly. The final images help the doctor determine the presence, size, and exact location of a tumor.

Functional MRI (fMRI)*

fMRIs produce MRI images that help identify parts of the brain responsible for important functions like speech or movement. This information can help a surgeon plan to remove a tumor without harming these functional areas. During this scan, you may be asked to answer questions or move certain parts of your body. These actions help identify the functional areas during the scan.

Flow-Sensitive MRI (FS MRI)*

This technique combines functional MRI with images of the flow of cerebrospinal fluid (CSF), a colorless liquid that fills and surrounds the brain and the spinal cord. FS MRIs are particularly useful in planning surgery to remove a skull base tumor, spinal cord tumor, or a tumor causing hydrocephalus (fluid buildup on the brain).

Perfusion MRI *

The type of scan works by seeing how blood moves through the brain. It can help to determine if a brain mass is a tumor or something else (e.g., abscess, stroke, radiation related change from prior radiation, or cells killed by radiation called radiation necrosis). It also helps predict what type of tumor it may be, or whether new growth of a tumor is actually tumor or if it is radiation necrosis or pseudoprogression.

CT Angiography (CTA) and Magnetic Resonance Angiography (MRA)*

These scans are used to locate blood vessels in the brain. This information can help the surgeon plan for tumor removal. This scan may be done with a contrast dye.

Magnetic Resonance Spectroscopy (MRS)*

This type of MRI provides information about the chemical make-up of brain tissue. It helps determine tumor type (which must be confirmed by biopsy), identify dead tissue (also called necrosis), or the difference between old and new tumor cells.

Positron Emission Tomography (PET, FDG-PET)

A PET scan shows how your brain is working as opposed to just the structure of the brain. Before the test, a small amount of radioactive material, (called a “tracer”), is injected into the bloodstream. The tracer will then collect into areas with actively dividing cells. Tumor cells are actively dividing so they will show up as bright spots on the scan. It may also help your doctor estimate the tumor’s grade and in some cases, it may help to tell the difference between recurrent tumor cells and necrosis (cells killed by radiation). The tracer leaves the body quickly and does not pose a safety risk to you or your loved one.

Single Photon Emission Computerized Tomography (SPECT):

SPECT is not usually used to diagnose brain tumors. However, it sometimes provides data that complements information captured in other scans. This data includes how malignant the tumor may be and the difference between tumor tissue and cells killed by radiation (necrosis).

*For these tests, the radiology facility will ask you to complete a form determining if they are safe. For instance, metal objects implanted in your body or certain medical conditions like kidney disease can pose safety risks.