IMAGE SURFACE SENSOR ARRAY FOR BIOMAGNETIC MEASUREMENTS

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We propose to complete construction of a novel whole-head super- conducting image sensor system for Magnetoenceph-alography (MEG) of the human brain, to experimentally calibrate and validate the system using physical phantoms, and to demonstrate system efficacy by direct comparison with a commercial whole-head MEG array. A cost-effective whole-head system will provide important capabilities for non-invasive functional human brain measurements for both clinical applications and basic research. MEG directly measures a physical effect for neuronal currents with temporal resolution not limited by the sluggish vascular response; unlike PET and fMRI that measure hematological changes associated with neuronal activity. High temporal resolution is particularly important for studying neurological disorders such as epilepsy where temporal information is a major diagnostic, and for fundamental studies of synchronization and oscillatory brain activity. The whole-head MEG system proposed here has been supported by NIH during the initial project period of this grant. The system is based on the Los Alamos-patented principle of super-conducting image surface gradiometry where magnetic sources are imaged on the surface and magnetometers near this surface sense the combined fields as if the sensors were MEG systems. The whole-head MEG system design is complete; fabrication and assembly are about 90% complete. Additional key accomplishments include (A) the super-conducting imaging principle was experimentally verified; (B) comparison of niobium and lead imaging surface performance demonstrated superior performance in the lead; (C) a new cryogenic sensor support material was patented; and (D) development of novel software and analog background rejection techniques. Support is now being requested to (1) complete assembly of the whole-head MEG system will all SQUID magnetometers; (2) complete flux-locked loop design implementing our new control and background cancellation techniques; (3) implement a powerful real-time data acquisition system with data management, display and analysis; (4) use phantom measurements to test and calibrate sensitivity, imaging and noise performance, and shielding characteristics of the sensor array; (5) experimentally verify system using a sophisticated phantom; and (6) acquire experimental data for human subjects under the same conditions as NIH-funded experimental studies of the visual and somatosensory systems. The work proposed here will result in a fully functional whole-head MEG system based on new physics applications, sensors design, and fabrication techniques that promise to dramatically reduce system cost and complexity while improving system performance. Such a system will be of great value to both basic neuroscience and clinical applications.