Biomagnetometer Maps the Brain

Healthy brain tissue can be damaged when a neurosurgeon cuts through the brain to reach the diseased area. A precise map of the brain’s activity would help minimize damage to functional areas. That map can now be created with information from a biomagnetometer.

Los Alamos National Laboratory recently developed the biomagnetometer, a new approach to measuring the minute magnetic fields generated by brain activity. By measuring these fields, precise maps of the brain functions can be created. The biomagnetometer uses a sensitive coil shielded by a layer of superconducting matter, which blocks other magnetic fields. The shielding is critical because the brain’s weak magnetic field would otherwise be “drowned out” by interference from naturally occurring magnetic fields, such as the Earth’s. Since other biological systems also generate weak magnetic fields, the biomagnetometer may be useful in examining the heart, lungs, and intestinal tract.

Magnetic sensing coils mounted in a superconducting helmet monitor brain function.

In 1982, Edward Flynn started the program at LANL. The Albuquerque Veterans’ Administration hospital and the University of New Mexico medical school began using the technology for clinical applications. Initially, the Veteran’s Administration program used a small machine to examine more than 1000 patients; since then, a large whole-head system has been used to examine four or five patients per day. This device has been used to examine more than 500 patients. In the next step of the LANL program, 100 detectors will be mounted in a helmet made of superconductor, allowing measurements in 1 hour that used to take weeks to obtain. The hospital and medical school are using the technology for epilepsy, pre-surgical localization of function, Alzheimer’s, schizophrenia, trauma, and stroke studies. Much of their work was reported recently at the International Conference on Biomagnetism in Santa Fe, with 500 people attending from around the world.

In addition to clinical applications, the potential exists for nondestructive examination of materials for microscopic cracks, corrosion, and imperfect welds. The system will detect the small electrical currents either generated by the imperfection or induced in the material. LANL has a cooperative research and development agreement with Conductus, a superconducting electronics firm in the San Jose area, to work on weak magnetic field sensors in general.

This research is funded by the Department of Energy’s Office of Health and Environmental Research and the National Institutes of Health. “I have an NIH grant that basically pays for the hardware and partial labor support for building the large system,” Flynn says, “I combine my grant with the OHER funding, which is for technological research in biomagnetism, to both build the large instrument and examine other problems associated with biomagnetism such as the inverse problem of electromagnetism, interpretation of data, data presentation and cross discipline comparisons of functional results on the human brain.”

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