Magnetic Resonance Spectroscopy

Nov. 14, 2025

This page was reviewed under our medical and editorial policy by Keng Lam, M.D., assistant clinical professor, Department of Medical Oncology & Therapeutics Research, City of Hope^® Cancer Center Duarte.

Doctors often use magnetic resonance imaging (MRI) to look for brain diseases. If a brain tumor is present, these scans are likely to show it.

Magnetic resonance spectroscopy (MRS), also known as MR spectroscopy or MRI spectroscopy, is a noninvasive imaging technique used in certain cases and often performed as part of an MRI.

What Is a Magnetic Resonance Spectroscopy?

MRS uses the same machine as an MRI, and both scans are routinely done together to provide a more complete picture of how the body tissues function. MRS adds another layer of technology —spectroscopy — to measure how the cells in those tissues are working.

Specifically, MRS looks at signals from hydrogen ions or protons inside the cells to show how they’re producing energy and breaking it down. This more in-depth view can help doctors compare healthy tissue to cancerous tissue. Cancer cells usually grow more quickly and produce more byproducts, which MRS can detect — helping to better identify problem areas.

Magnetic resonance spectroscopy can help doctors determine tumor type, aggressiveness or recurrence. MRS can also show how well a tumor is responding to treatment — for example, helping doctors tell whether an area that still looks abnormal on another scan is remaining cancer or just scar tissue.

MR Spectroscopy vs. MRI

While both magnetic resonance imaging and magnetic resonance spectroscopy can help doctors explore the health of soft tissues and organs, they differ in the insights they offer.

An MRI gives doctors a detailed look at the structure of the soft tissues and organs — including fat and water content, blood flow and possible damage to arteries. This can offer helpful clues about how healthy the patient’s tissues are. But when paired with MRS, the scan provides even deeper insight.

Here’s how it works: During an MRI, strong magnets temporarily shift the natural alignment of protons in the body. When the magnets are turned off, the protons slowly return to their normal positions. The MRI machine uses radio waves and a computer to measure how long that process takes — something called T1 or T2 relaxation time — which helps assess the health of cells. MRIs are useful for scanning many parts of the body, including the brain, spine and internal organs.

MRS goes a step further by helping doctors look at how the cells are functioning, especially how they’re producing energy. As cells break down nutrients, they create tiny chemical byproducts called metabolites. By tracking the type and number of metabolites, MRS can show how active or abnormal a group of cells may be — often providing early signs of conditions like cancer or brain disease.

Typically, MRS is done alongside an MRI and may include a contrast dye to help highlight certain tissues and disease progression. After the scan, a computer generates a graph showing the metabolite activity in the tissue. This information helps the care team understand whether the tissue is behaving normally, how aggressive a disease might be, or how well treatment is working.

To summarize, MRI shows where a tumor is located in the brain, while MRS compares the chemical makeup of normal brain tissue with abnormal tumor tissue.

How to Prepare

The following checklist can help patients prepare for a combined MRS and MRI procedure:

• Wear comfortable clothes that make it easier to change into and out of a hospital gown.
• Remove any metal jewelry, hearing aids or body piercings.
• Disclose any implants or prior work with metal.
• Share any prescription information.
• Stick to clear fluids. If the scan requires a contrast agent, avoid caffeine 24 hours before the appointment.
• Complete required bloodwork if a contrast agent will be used.

How Long Does It Take?

A radiology technologist will perform the test in the MRI suite in a hospital’s radiology department or an outpatient imaging center.

Whether performed by a radiology technologist in a hospital’s radiology department or an outpatient imaging center, an MRS procedure may take slightly longer than a conventional MRI, which usually last around 45 minutes to an hour.

Benefits, Risk and Limitations

MRI and MR spectroscopy are considered very safe. Importantly, they don’t use radiation or harm surrounding healthy tissue, and there are no known risks from the magnetic field or radio waves used during the scan.

A small number of people may feel mild discomfort. Here are some things to be aware of:

• Anxiety or claustrophobia: If the patient typically feels nervous or uneasy in enclosed spaces, talk to the care team or radiologist ahead of time. Mild sedatives can be prescribed to help the patient stay calm during the scan.
• Tattoos: Some tattoo inks contain tiny metal particles that can heat up slightly during the scan. Let the technician know right away if any warmth occurs in tattooed areas.
• Pregnancy: Always let the care team know if the patient is pregnant or thinks she might be. While MRI can sometimes be done during pregnancy, it’s usually avoided unless medically necessary for the patient’s health or the baby’s.
• Allergies: The contrast dye used in scans is FDA-approved and safe, but some people may feel flushed or warm afterward. Allergic reactions rarely occur. Tell the care team about any allergies to contrast dye, medications or iodine, before the scan.