Delivering a baby MEG

baby MEG
This array of sensors surrounding a baby’s head will give researchers and eventually clinicians a high-resolution image of neural activity.

Imagine you’re a clinician or researcher and you want to find the source of a newborn’s seizures. Imagine being able to record, in real time, the neural activity in his brain and to overlay that information directly onto an MRI scan of his brain. When an abnormal electrical discharge triggered a seizure, you’d be able to see exactly where in the brain it originated.

For years, that kind of thinking has been the domain of dreams. Little is known about infant brains, largely because sophisticated neuroimaging technology simply hasn’t been designed with infants in mind. Boston Children’s Hospital’s Ellen Grant, MD, and Yoshio Okada, PhD, are debuting a new magnetoencephalography (MEG) system designed to turn those dreams into reality.

Several years ago, Grant, who founded the Fetal-Neonatal Neuroimaging and Developmental Science Center at Boston Children’s, heard Okada give a talk on MEG systems. Realizing their potential for understanding brain disorders and injury in newborns, Grant approached Okada about creating a MEG facility at the hospital, and Okada set out to design and construct it. A grant from the National Science Foundation was instrumental.

Like existing MEG systems designed for older patient populations, “baby MEG”—as Grant and Okada affectionately refer to it—uses highly sensitive, helium-cooled magnetometers connected to SQUIDs (superconducting quantum interference devices) to record, measure and map the magnetic fields created by the brain’s electrical activity. Unlike earlier iterations of MEGs, however, baby MEG boasts several unique features.

Extra “sensory” perception

Because it’s loaded with extra sensors—375 compared with the 300 typically found on existing MEGs—the images baby MEG produces will be rendered with unprecedented spatial resolution, giving clinicians a clearer and sharper picture of a patient’s neural activity.

That clearer, sharper image has the potential to advance research into a wide range of pediatric conditions like cerebral palsy, Down syndrome, fetal alcohol syndrome and especially epilepsy, where Grant and Okada see great potential for complementing the EEGs that neurologists currently use.

baby MEG
MEGs are passive, non-invasive systems designed to complement information from MRI, PET and other imaging technologies. MEGs are surprisingly quiet, allowing sleeping infants to be tested undisturbed.

Okada collaborated with Mass General Hospital’s Martinos Center and the Director of its MEG Core facility, Matti Hämäläinen, PhD, to create software that will enable baby MEG to display its data in real time. “You could actually sit there and watch it instead of waiting for it to process and then taking it to a computer,” Grant explains.

Baby MEG is also able to recycle 100 percent of its liquid helium, which is used to cool the system’s sensors to minus 452 degrees Fahrenheit, at which point the sensors lose their resistance and become extremely sensitive to magnetic fields. That may not sound like a big deal, but helium is increasingly scarce. In the United States, 42 percent of helium demand is met by a government-run national reserve. (That arrangement that nearly led to a shortage last year, averted when the Senate renewed the relevant legislation at the last minute.) Baby MEG’s helium recycler will help ensure a longer life for the system.

Putting epilepsy on the map

Baby MEG adds some key advantages in evaluating epilepsy. MEGs are less hampered by soft tissue swelling, which can make it difficult to accurately localize seizures by EEG. And they are much better than EEGs at picking up certain patterns of abnormal electrical activity associated with epileptic seizures. “The magnetic field is specifically very good at picking up some discharges that are tangential to the surface, for example, in the inter-hemispheric fissure or that are hidden deeper in the brain,” explains Tobias Loddenkemper, MD, a neurologist at Boston Children’s.

For Loddenkemper, the greatest advantage may lie in surgical planning. “We will be able to see which areas of the brain should be avoided and must not be resected when planning epilepsy surgery in infants,” he explains. By mapping functional brain activity, the system can help pinpoint brain areas responsible for early language processing and other important cortical functions.

From the lab to the cradle

Currently, EEGs are used much more frequently than MEG systems in pediatric epilepsy care and for good reason: they’re much smaller, they’re portable and they don’t need to be housed in heavy, expensive magnetically shielded rooms.

The need for such housing is generally the reason most MEGs are located in the basement of research centers far from hospitals—and the critically ill patients who need them most. In designing baby MEG, Okada worked with San Diego’s Tristan Technologies to find a way around that.

The product of that collaboration is a magnetically shielded room that is both light enough to be safely installed above ground and effective enough at containing magnetic and electrical interference to be placed next to the NICU. “Within the clinical infrastructure of a hospital, this is the only such structure in the world, and that will give us a very critical advantage for studying children,” Okada says.