Intraoperative magnetic resonance imaging (iMRI) is a procedure that creates images of the brain during surgery. Neurosurgeons rely on iMRI technology to obtain accurate pictures of the brain that guide them in removing brain tumors and treating other conditions such as epilepsy.

Advantages of iMRI

Although doctors use imaging tests to plan brain surgery, real-time images created with iMRI are crucial to:

  • Locate abnormalities if the brain has shifted. The brain often shifts during surgery, which makes pre-surgical imaging not exactly precise. Imaging with iMRI during the operation helps to provide surgeons with the most accurate information.
  • Distinguish abnormal brain tissue from normal brain tissue. It can be difficult to distinguish the edges of a brain tumor and separate normal tissue from abnormal tissue. Imaging with iMRI during surgery helps confirm successful removal of the entire brain tumor.
  • Protect critical structures. A procedure called laser interstitial thermal therapy (LITT) allows surgeons to treat epilepsy by heating tissue and making it inactive, disrupting the flow of seizures through a minimally invasive approach. By using iMRI to monitor brain temperature, surgeons are also able to keep temperatures low enough to avoid injury during the procedure, In MR-guided ultrasound, surgeons can focus ultrasound energy on areas of the brain causing epilepsy without performing surgery.

    Intraoperative MRI allows surgeons to achieve a more complete removal of some brain tumors. For this reason, iMRI has become standard for many operations to remove certain brain tumors.

How iMRI works

MRI uses a magnetic field and radio waves to create detailed images of the organs and tissues in your body. MRI is especially helpful for imaging the brain.

To utilize MRI technology during surgery, doctors use special imaging systems and operating rooms, including:

  • Portable iMRI devices, which are moved into the operating room to create images.
  • Nearby iMRI devices, which are kept in a room near the operating room. This way, doctors can easily move you to the specially designed room for imaging during your surgery.

At certain points in your operation, the surgeon may request imaging with iMRI. When and how often the surgeon creates images during surgery depends on your procedure and your condition.

Uses for iMRI

Doctors use iMRI to assist in surgery to treat:

Why it's done

Surgeons use iMRI to assist in procedures that treat a variety of brain tumors. Surgery is often the first step to treat a tumor that can be removed without causing neurological damage. Some tumors have a clearly defined shape and can be removed easily.

In addition, surgeons use iMRI to place deep brain stimulators to treat epilepsy, essential tremor, dystonia and Parkinson's disease. iMRI is also used to assist in surgery for some brain conditions, such as a bulge in a blood vessel (aneurysm) and tangled blood vessels (arteriovenous malformation) as well as mental health disorders.

During these procedures, iMRI allows surgeons to monitor brain activity; check for bleeding, clots and other complications; prevent damage to surrounding tissue; and protect brain function. This helps with earlier intervention to address complications and may reduce the need for additional operations. For cancer surgery, iMRI helps surgeons ensure that the entire tumor has been removed.

What you can expect

Surgeons use iMRI to create real-time brain images. At certain points during an operation, the surgeon may want to see certain images of the brain. MRI uses a magnetic field and radio waves to create detailed brain images.

To use MRI technology during surgery, doctors may bring a portable iMRI machine into the operating room to create images. They may also keep the iMRI machine in a room near the operating room so surgeons can easily move you there for imaging during the procedure.

iMRI cannot be used in patients with most pacemakers, cochlear implants, and metal joints or certain implants.

Intraoperative magnetic resonance imaging (iMRI) care at Mayo Clinic

March 05, 2022
  1. Dietrich J, et al. Clinical manifestation, diagnosis, and initial surgical management of high-grade gliomas. https://www.uptodate.com/contents/search. Accessed Nov. 27, 2021.
  2. Winn RH, ed. Youmans and Winn Neurological Surgery. 7th ed. Elsevier; 2017. https://www.clinicalkey.com. Accessed Nov. 27, 2021.
  3. Van Gompel J (expert opinion). Mayo Clinic. December 6, 2021.
  4. Rogers CM, et al. Intraoperative MRI for brain tumors. Journal of Neuro-Oncology. 2021; doi:10.1007/s11060-020-03667-6.
  5. Brain and spinal cord tumors: Hope through research. National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Hope-Through-Research/Brain-and-Spinal-Tumors-Hope-Through. Accessed Dec. 4, 2021.
  6. Brown DA, et al. Cranial tumor surgical outcomes at a high-volume academic referral center. Mayo Clinic Proceedings. 2018; doi:10.1016/j.mayocp.2017.08.023.
  7. Venkatraghavan L. Anesthesia for deep brain stimulator implantation. https://www.uptodate.com/contents/search. Accessed Dec. 4, 2021.
  8. Find an NCI-Designated Cancer Center. National Cancer Institute. https://www.cancer.gov/research/infrastructure/cancer-centers/find/mayoclinic. Accessed Dec. 29, 2021.


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