Biomeganetometry was discussed at the 75th Annual Meeting of the Radiological Society of North America. Unlike ultrasound, CT, and MRI (which provide anatomic information) and PET (metabolic information), biomagnetic imaging provides spatial and temporal data on the electrical activity of the brain. It may help locate the foci of epileptic seizures and show locations for language, auditory and visual processing. Unlike the EEG which is crude and looks at ripples in the water, biomagnetometry shows the stone and the source of the ripples (Dr. Harwood-Nash, Toronto). EEG signals travel through many types of tissue with varying degrees of electrical resistance and consequent distortion. The magnetic flux generated by neurons are not distorted by bone or other biologic tissues, they are picked up and converted to electrical signals by detection coils, amplified, filtered and processed for display on a computer screen to show spatial distribution and time evolution of the electrical activity being scanned. The information is presented graphically superimposed over a single plane MRI image so that correlations with the anatomical structures can be made. In 15 of 40 patients with epilepsy who received biomagnetic scans and underwent surgery for the removal of epileptic foci, there was good correlation between EEG and biomagnetometry mapping of the epileptic foci. (Sato S. Bethesda, MD). [1]

COMMENT. Biomagnetic Technologies (BTi), a San Diego company, has installed more than 50 seven channel machines and announced the availability of a 37 channel biomagnetometer at the RSNA November 1989 meeting. Siemen's expects to install its first 37 channel system (Krenikon) in West Germany and three at research centers in the U.S. A large area, 7-channel, magnetometer (SQUID) was used to preoperatively determine the sites of epileptic foci in two patients with intractable temporal lobe seizures and results are reported from the Department of Neurosurgery, Kuopio University Hospital, Finland. Preop localization agreed with electrocorticogram and depth electrode operative recordings. [2]