Abstract:

Currently, linear estimation reconstruction is the only feasible method for extracting information about spatially distributed current sources from measurements of neural magnetic fields. We present the results of a systematic study of the effect of the signal-to-noise ratio on the imaging quality of one such algorithm in over-as well as undetermined circumstances. In particular, we will discuss the necessary trade-off between the contradictory goals of a minimum norm of the reconstructed current density distribution and of a minimal deviation of the reconstructed fields from the measured fields. As an example, we show the reconstruction of a simple arrangement of two nearly parallel dipoles in two different depths inside a spherical volume conductor, discussing the differences between the computer simulation without noise and simulation with a realistic noise level.

Abstract:

The principle of interferometry has been applied to thin polymer films as they swell by sorption of gases or as they interact with biochemical material. Modern diode array technology allows the monitoring of changes in optical path-length at a fractional nanometre scale. Observation of the interference spectra makes discrimination between thickness and Fresnel refractive index effects possible. Thus, very sensitive sensors can be developed for measuring concentrations of gaseous and liquid organic solvents as well as specific antigen-antibody interactions.

Abstract:

Papers from the 4th International Conference on Superconducting and Quantum Effect Devices and their Applications held in Berlin, Germany, June 18-21, 1991.Detailliertere InformationenSuperconducting devices and their applications: proceedings of the 4th international conference SQUID '91 (session on superconducting devices), Berlin, Fed. Rep. of Germany, June 18-21, 1991Von Hans Koch, H. LübbigMitwirkende Personen Hans KochEdition: illustratedVeröffentlicht von Springer-Verlag, 1992Original von University of MichiganDigitalisiert am 10. Dez. 2007ISBN 0387553967, 9780387553962603 Seiten

Abstract:

Neuromagnetic imaging is a relatively new diagnostic tool for examination of electric activities in the nervous system. It is based on the noninvasive detection of extremely weak magnetic fields around the human body with superconducting quantum interference device (SQUID) detectors. `Equivalent current dipoles' and linear estimation reconstructions of current distributions both with spherical volume conductor models are used to localize the neural activity. For practical use in medical diagnosis a combination of the abstract neuromagnetic images with magnetic resonance (MR)- or computer tomography (CT)-images is required in order to match the functional activity with anatomy and morphology. The neuromagnetic images can be overlayed onto three-dimensional morphological images with spatially arbitrarily selectable slices. The matching of both imaging modalities is discussed. Based on the detection of auditory evoked magnetic fields, neuromagnetic images are reconstructed with linear estimation theory algorithms. The MR images are used as a-priori information of the volume conductor geometry and they allow an attachment of functional and morphological properties.