IMAGE SURFACE SENSOR ARRAY FOR BIOMAGNETIC MEASUREMENTS

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The present proposal is to construct, test and put into practice a new concept in biomagnetic sensor arrays for neuromagnetic measurements for both basic research and clinical applications. Neuromagnetism is an increasingly useful method for studying neural sources in these areas. The proposed, less expensive array of sensors could substantially augment this usage. This new concept, which relies on the use of super-conducting image surfaces to provide gradiometer response from single coils, has a number of distinct advantages over existing biomagnetic sensor array designs. These advantages are: (1) the construction of a large array of sensor coils is much simpler in the imaging surface gradiometer design than with standard axial gradiometer methods, resulting in a potential significant reduction in cost; (2) there is increased sensitivity due to a smaller number of coils required to share the energy generated by neural sources; (3) the superconducting image surface, in the shape of a hemispherical shell, produces a large screening effect on external fields which, when combined with the gradiometer action, significantly reduces the need for an expensive shielded room; and (4) the assembled array is less bulky than an array of normal axial gradiometers. The super-conducting image surface gradiometer concept has been verified in the laboratory and extensive theoretical calculations carried out to ascertain its effectiveness under various conditions. The goal is to construct a large array of 93 sensors which would cover approximately 120 degrees of the head simultaneously. Instead of requiring 93 accurately wound axial gradiometers, the new technique would require only a single hemispheric cap with a superconducting surface deposited on one side and a set of 93 coils deposited on the other. Each coil is connected to a SQUID to provide the flux-to-voltage conversion. The array will be built in stages starting with 7 SQUIDs and then gradually enlarging the array. This large array of sensors would be tested initially in the Los Alamos neuroscience program. Subsequent clinical trials would be carried out at the Albuquerque VA biomagnetic facility which is a Los Alamos - VA - UNM collaboration. The analysis of data obtained from this large array would be carried out by newly developed spatial-temporal methods at Los Alamos, as well as new theoretical methods in calculating the location and nature of neural sources.