Brain Tumor Diagnosis – Magnetic Resonance Imaging (MRI)
A brain tumor is an abnormal cluster of cells in the brain or the tissues surrounding it. The mass may be benign (noncancerous) or malignant (cancerous). There are two main types: primary and metastatic. A primary brain tumor begins in the brain, while a metastatic brain tumor spreads to the brain from cancer that developed elsewhere in the body.
Scientists believe brain tumors form when brain cells undergo harmful DNA changes that cause them to grow and divide uncontrollably. Often, the precise cause is unknown.
As a brain tumor grows, it may begin to press on healthy brain tissues and interfere with neurological functions, such as speech, movement and thought. While the warning signs can vary based on the size, type and location of the tumor, possible symptoms include persistent headaches, seizures, memory problems, personality changes, speaking difficulties, vision changes, weakness, numbness and balance issues.
Although brain tumors are relatively uncommon compared with many other types of cancer, thousands of people in the United States are diagnosed each year. An early and accurate diagnosis is key to developing an effective treatment plan.
How are brain tumors detected?
The diagnostic process for a brain tumor typically begins with a detailed medical history review followed by a neurological examination, which may include an evaluation of:
- Cognitive function and memory
- Coordination and balance
- Reflexes
- Strength and sensation
- Vision, hearing and speech
If a brain tumor is suspected based on the initial clinical assessment, the physician may order advanced imaging and other specialized tests to confirm the diagnosis, pinpoint the location of the tumor and identify its type.
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Schedule an AppointmentMRI is the primary type of imaging used to diagnose brain tumors. This well-established, noninvasive test uses radio waves and a powerful magnetic field to generate high-definition images of the brain and surrounding structures without exposing the patient to radiation.
What is the purpose of an MRI in diagnosing a brain tumor?
Magnetic resonance imaging may be performed to check for abnormal areas in the brain and, if any are found, help the physician evaluate the:
- Effect on surrounding tissues
- Location
- Pattern of contrast enhancement
- Shape
- Size
MRI can help the physician determine whether a mass is present, whether it appears consistent with a tumor and how it may be affecting nearby brain structures. It can also provide detailed information to help guide biopsy, surgery and overall treatment planning.
What types of MRI scans are used to diagnose brain tumors?
Different types of magnetic resonance imaging can provide specific information about a brain tumor. Some techniques may help show the tumor’s boundaries more clearly, while others may provide clues about its activity, blood supply or proximity to areas of the brain that control critical functions.
Intravenous (IV) gadolinium-enhanced MRI
IV gadolinium-enhanced MRI is a diagnostic imaging procedure for brain tumors that uses a contrast medium (gadolinium), which is administered intravenously before the test. Gadolinium collects around cancerous cells, which can make abnormal tissues appear brighter and more defined on the images. This can improve diagnostic accuracy by helping the physician distinguish tumor tissue from the surrounding brain structures. While generally safe, IV gadolinium-enhanced MRI may cause mild side effects, such as dizziness and headaches.
Diffusion-weighted imaging (DWI)
DWI evaluates how water molecules move through brain tissue. Because a tumor can change the way water diffuses, this technique can help the physician assess the tumor’s nature, structure and cellularity. It can also provide information about white matter tracts, which are pathways that carry signals between different areas of the brain. In addition to brain tumor evaluation, diffusion-weighted imaging may be used to help identify or rule out a stroke.
Diffusion tensor imaging (DTI)
A specific type of diffusion-weighted imaging, DTI maps the brain’s white matter pathways. Often used for surgical planning, this advanced MRI technique can help the neurosurgeon see how close a tumor is to critical nerve pathways and determine whether those pathways are displaced or affected. This information can help guide a surgical approach that helps avoid essential pathways when possible and supports safer tumor removal.
Perfusion imaging
Perfusion imaging measures blood flow in the brain and can help the physician assess the tiny blood vessels that supply a tumor. Because some tumors develop a stronger blood supply as they grow, perfusion imaging can provide clues about how active the tumor may be. This information can help the physician better understand the tumor’s behavior, distinguish among tumor types and support treatment planning.
Functional MRI (fMRI)
During an fMRI examination, the patient will be asked to complete certain tasks while lying still, such as thinking about specific topics or performing silent exercises. These tasks will cause tiny blood flow changes in the active part of the brain, which can be seen on fMRI images. Often used for diagnostic purposes and surgical planning, functional MRI can identify the brain areas responsible for critical functions, such as speech and muscle movement, which can help the physician plan the safest treatment approach for a nearby tumor.
Magnetic resonance spectroscopy (MRS)
MRS provides information about the chemical composition of brain tissue. Rather than showing anatomy alone, this imaging test can reveal chemical patterns that may be associated with tumor cells. It can help the physician identify cancerous cells, better understand the type of tumor that may be present and monitor changes that could suggest tumor progression or treatment response.
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Other types of imaging used to diagnose brain tumors
Although MRI is the primary imaging test for brain tumors, other imaging studies may be used in certain situations, such as to help the physician evaluate urgent symptoms, confirm findings seen on magnetic resonance imaging or obtain additional information. Other imaging modalities may also be used if MRI is not possible.
Computed tomography (CT) scan
A CT scan uses multiple X-rays captured from different angles to create cross-sectional images of the brain. Computed tomography is fast, widely available and ideal for initial imaging to rule out immediate, acute or life-threatening issues. For example, a CT scan can help the physician quickly detect bleeding, swelling or a large tumor. It is often used in emergency situations, such as when the patient presents with severe symptoms, or if the patient cannot undergo an MRI.
Nuclear medicine/functional imaging
In some cases, a nuclear medicine imaging test, such as a positron emission tomography (PET) scan, may be used to diagnose a brain tumor. For this test, a small amount of radioactive tracer will be injected into a vein. After traveling through the bloodstream, the tracer will be absorbed by cells in the brain. Because active cells use more energy, they will absorb more of the tracer, allowing the scan to highlight areas with increased metabolic activity. This can help the physician identify tumor sites, distinguish between active tumor tissue and scar tissue and assess treatment-related changes.
Can an MRI tell if a brain tumor is cancerous?
Magnetic resonance imaging can provide important clues about whether a brain tumor might be cancerous, but it cannot confirm it on its own. Certain findings, such as the pattern of contrast enhancement, signs of rapid growth or evidence that the tumor is affecting nearby tissues, may raise concerns about cancer. Still, imaging cannot definitively determine whether a tumor is benign or malignant.
Usually, a biopsy is needed for a confirmed diagnosis. During this procedure, the physician will remove a small amount of suspicious tissue for microscopic examination by a pathologist, who can conclusively identify cancerous cells. The sample may also be analyzed for molecular markers, which are specific genetic or biochemical features found in tumor cells. Identifying these markers can help the physician more accurately classify the tumor, estimate how aggressively it may behave and determine which treatments are most likely to be effective. Molecular testing is now an important part of diagnosing many brain tumors and developing an individualized treatment plan.
Biopsy techniques used to diagnose brain tumors include:
Stereotactic needle biopsy
A stereotactic needle biopsy is a minimally invasive procedure in which a neurosurgeon uses advanced imaging guidance to insert a thin needle through a small opening in the skull to obtain a tissue sample. This approach is often used for tumors located deep within the brain or in other difficult-to-access areas.
Surgical biopsy or resection
In some cases, surgery may be performed to remove part or all of the brain tumor. During the procedure, a pathologist will examine the tissue under a microscope to confirm the diagnosis. Removing as much of the tumor as safely possible can also help relieve symptoms caused by pressure on the brain.
Benefit from world-class care at Moffitt Cancer Center
The multispecialty team in Moffitt’s comprehensive Neuro-Oncology Program utilizes advanced imaging technologies, sophisticated laboratory testing and state-of-the-art surgical techniques to evaluate and treat brain tumors. Specialists in neuro-oncology, neurosurgery, neuroradiology, neuropathology and radiation oncology collaborate closely to ensure each patient receives an accurate diagnosis and an individualized treatment plan. We are also actively involved in research and clinical trials designed to improve outcomes and quality of life for patients with brain tumors.
If you would like to learn more about the role of magnetic resonance imaging in diagnosing brain tumors, you can request an appointment with a specialist in the Neuro-Oncology Program at Moffitt by calling 1-888-663-3488 or submitting a new patient registration form online. We do not require referrals.
