THE BRAIN AND EPILEPSY
UCI researchers are developing a noninvasive, cheaper and more accurate method for mapping brain regions related to epileptic seizures, autism
Pre-surgical teams may soon have a more reliable, cost effective and noninvasive way to help pinpoint areas in a patient’s brain causing epileptic seizures.
A new method for magnetoencephalography (MEG), developed by UCI professors, will allow researchers to measure brain activity at a millimeter scale with millisecond temporal resolution. The technique also has applications in noninvasive mapping of brain function and brain connectivity in disorders such as autism.
“Measuring the magnetic field of the brain using MEG is potentially the best approach for accurately mapping brain activity because it has very high temporal resolution and can be used to localize brain activity through magnetic source imaging,” says Ramesh Srinivasan, UCI cognitive sciences and biomedical engineering professor.
However, current MEG technology uses expensive coils that must be kept at absolute zero temperature; as a consequence, there’s a more than three-centimeter-thick layer of insulation between the scalp and sensor.
The impact of this distance, says Srinivasan, is weaker signals from the brain and reduced spatial resolution. The equipment costs are also in the millions of dollars, and the liquid helium cooling systems are expensive to maintain.
Working together with Jing Xia, astronomy and physics associate professor, Srinivasan is developing a method to measure MEG using sensors at room temperature that are placed directly against the scalp. They will adapt Sagnac interferometer technology developed by Xia for magnetic field measurements in physics application. The Sagnac interferometer uses laser-charged, pure atomic vapor as a sensing media that will measure the brain’s magnetic field.
The laser aligns all of the atomic spins; if there’s no magnetic field, they’ll spin in one particular direction. If a magnetic field is imposed on it, the spins of the atoms are modified which can be detected by the interaction of the atomic media with a probe laser.
In epilepsy research, the new equipment and procedure would provide useful information on where seizures are occurring without a doctor opening a patient’s skull.
“We estimate that the cost of the Sagnac MEG will be one-tenth the cost of a conventional MEG machine, with five times higher spatial resolution and 10 times higher sensitivity,” Srinivasan says. “This will potentially allow for recording from deep brain structures.”
The technology has immediate impacts in pre-surgical mapping by clinicians and numerous possibilities in basic and clinical research on disorders including autism and epilepsy.
“In epilepsy research, the new equipment and procedure would provide useful information on where seizures are occurring without a doctor opening a patient’s skull, potentially reducing the need for extensive intracranial mapping,” Srinivasan says.
He and Xia are affiliated with UCI’s Center for Autism Research and Translation, which provided seed funding for this research. One of their long-term goals is to apply MEG for noninvasive brain mapping of connectivity in autistic patients.
“One of the most reliable markers of autism is changes in connectivity measured using EEG,” Srinivasan says. “Professor Xia and I would like to perform this research with our new MEG technology to improve the specificity of brain areas showing changes in connectivity.”
The scientists have received $367,000 from the National Institutes of Health to modify the interferometer to work for MEG. When complete, they’ll begin testing with phantom heads and then on human subjects.