Mapping the body's electrical fields

by Holly Korab

Hundreds of times each second, the brain sends electrical impulses racing through the body's web of nerve cells to the motor neurons, where they initiate the chemical reactions that cause muscles to contract.

About a century ago, scientists recognized that these excitation currents produce an electrical field which can be detected as small voltages in the skin or scalp. By measuring changes in the patterns of the body's electrical activity, researchers could detect some forms of heart disease and neurological disorders. Electrocardiograms of the heart (ECGs) or electroencephalograms of the brain (EEGs) measure these voltages; however, they provide physicians with only a snapshot of heart or brain activity. These glimpses help doctors spot disorders but are not always sufficient for diagnosing them. For the latter, doctors turn to other techniques; in rare cases, to surgery.

Such is the case with some abnormal heart rhythms (arrhythmias). For patients who do not respond to drug treatment or pacemakers, cardiac surgeons often must open the chest and examine the heart with a roving, hand-held electrode or a flexible grid of surface electrodes to determine just where to operate.

For temporal lobe epilepsy, neurosurgeons determine whether a patient who is not responding to medication has an operable form of the disorder by opening the cranium and attaching electrodes directly to the brain to identify whether the disordered electrical activity is highly localized (thus operable) or diffused over the entire brain.

Revolutionizing diagnostic procedures

A team of computer scientists, physiologists, and physicians at the University of Utah are developing a diagnostic tool so that doctors may not have to undertake risky preoperative procedures. Using NCSA's POWER CHALLENGE, Christopher Johnson, associate chairman of computer science; Robert MacLeod, assistant professor of internal medicine; Peter Heilbrun, chairman of the Department of Neurological Surgery; and John Schmidt, research associate of computer science, are simulating the electrical fields emanating from the heart and brain to replace the snapshots from ECGs and EEGs with full-scale, 3D models. Johnson is team leader for Utah's Scientific Computing and Imaging Group (SCI).