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Advanced technology plays a critical role in safely removing brain tumors. One key technology that does this is magnetoencephalography (MEG). MEG can measure the brain’s electrical activity down to the millisecond.

It allows neurosurgeons to plan surgeries to remove brain tumors and other brain pathologies. It does this while preserving critical brain functions. These include language, motor skills, and vision.

“Neurosurgeons want to protect neurologic function while approaching the tumor during surgical removal,” says Ajay Niranjan, MD, director, UPMC MEG Brain Mapping Center.

“If MEG can inform the neurosurgeon the exact location of language function, for example, then the surgeon can approach the tumor from a safer approach to avoid any damage to those areas and preserve language.”

According to Constantinos Hadjipanayis, MD, PhD, director of the UPMC Center for Image-Guided Neurosurgery and co-director of the UPMC Brain Tumor Program, “Preoperative MEG planning is quite informative and contributes to the best surgical outcomes for our brain tumor patients. Dr. Ajay Niranjan and his MEG team routinely perform these important studies for our patients.”

UPMC routinely uses MEG imaging to plan for brain tumor removal and localize brain areas that may cause seizures and epilepsy. We are the only center in Pittsburgh using MEG. We are also the only center in Pennsylvania using it for brain tumors.

Learn more about MEG, including how it works and how it helps with brain tumor removal, below.

What Is Magnetoencephalography?

MEG is a noninvasive test that measures your brain activity based on your brain’s magnetic fields.

“Basically, it is a technique that picks up the tiny magnetic signals that arise from the electrical currents in the brain,” Dr. Niranjan says. “When in the brain, current is flowing, that magnetic signal comes out, and this machine can detect that magnetic signal.”

MEG can measure brain activity down to the millisecond, with millimeter-level precision. Because of this accuracy, it’s currently the most advanced technology for mapping brain activity.

How Does MEG Work?

MEG is sensitive to other electromagnetic signals. The machine must stay in a special magnetically shielded room.

During the test, patients wear a specialized helmet that contains 306 sensors known as superconducting quantum interference devices (SQUIDs). The SQUIDs can pick up tiny magnetic signals from the brain. Cooling them in liquid helium at a temperature of about -270.0 C is necessary to do this.

Patients may stay awake or sleep during the test. They may have to answer questions or perform simple tasks. The SQUIDs pick up the tiny magnetic signals from the brain.

Providers use algorithms and software to clean up the data collected and pinpoint the areas of different brain functions. They then project the MEG data onto a magnetic resonance image (MRI) of the patient’s brain.

This magnetic source imaging (MSI) maps different brain functions.

“It is a mixture of neuroscience, signal analysis, signal processing, computer science, and of course, neurosurgery and neurology,” Dr. Niranjan says. “It’s not just an isolated field.”

Neurosurgeons receive the MRI with different functions mapped and can use it to plan their procedures.

“I get the MEG, and I understand the location of the tumor in relationship to surrounding critical structures: language, motor, (and) even vision,” Dr. Hadjipanayis says. “That now lets me start thinking: How am I going to approach the tumor safely?”

How Does MEG Help with Removing Brain Tumors?

MEG is the most advanced technology for mapping brain activity.

It has millimeter precision. It can also detect activity to the millisecond. This makes it faster and more precise than other tests.

By comparison:

• A functional MRI (fMRI) exam can pick up magnetic signals every one to three seconds. That makes MEG at least 1,000 times faster.
• An electroencephalogram (EEG) can pick up the electric current at the scalp level. MEG picks up the electric current in the brain itself before any distortion can happen

“There are many tools for us to look into the brain, but magnetoencephalography, I would say, is much superior to both EEG and functional MRI,” Dr. Niranjan says.

MEG is also a safe test. It’s noninvasive and doesn’t need x-rays or strong magnetic fields. This makes it different from other tests.

But its biggest benefit comes in surgical planning. MEG’s precision allows neurosurgeons to remove a tumor without affecting key brain functions. These functions include language and motor skills.

This planning helps ensure patients have no long-term complications from surgery. It also safely removes as much of the tumor as possible.

“The name of the game is: How do we perform more effective, more complete tumor resections while preserving and improving neurologic function?” Dr. Hadjipanayis says. “The game’s lost if someone’s neurologic function gets worse, and that’s why we need these tools and technologies to keep things intact or make it better after surgery. We’ve been able to thread that needle well here with our approaches.”

MEG helps neurosurgeons determine whether they can remove the area of an epilepsy patient’s brain that causes seizures without affecting brain functions.

How Is UPMC a Leader in Magnetoencephalography?

The UPMC Center for Image-Guided Neurosurgery has used MEG for more than 15 years. We have extensive experience in analyzing the data collected by MEG and using it to map the brain.

“We have good experience with this technology,” Dr. Niranjan says. “We have actually developed our own algorithm, our own method of doing analysis, and putting those pictures in the format that surgeons would prefer.”

Surgical planning for glioma tumors is UPMC’s main use for MEG. Other uses include treating meningioma tumors, arteriovenous malformations (AVMs), and epilepsy.

Research to determine further uses of the technology in neurosurgery is in progress.

Dr. Niranjan says MEG has helped significantly when it comes to surgical planning at UPMC.

“It certainly increases the confidence of the surgeon, but if the patient knows that this is what is done for them, the patient also has increased confidence in the surgery,” he says. “They know that, ‘OK, my surgeon has all the data. They have everything that they need to know to do a safe surgery.’’’