Accession Number:

ADA411107

Title:

Biomagnetic Inverse Solution Using Combined-Norm and Pointwise Normalization

Descriptive Note:

Conference paper

Corporate Author:

TOKYO UNIV (JAPAN) GRADUATE SCHOOL OF FRONTIER SCIENCES

Personal Author(s):

Report Date:

2001-10-25

Pagination or Media Count:

5.0

Abstract:

In this paper, we propose a method of solving the biomagnetic inverse problem consisting of two approaches, the first of which is pointwise normalization. In the conventional normalization technique, each variable is normalized individually. This variablewise normalization is appropriate for scalar fields, but not for vector fields where one vector on a grid point is represented by several variables. Hence, pointwise operation is needed for vector fields, The second is a combination of norms. Use of the l sub 2-norm as the cost function of an optimization problem is known to lead to spatially spread solutions, while the l sub 1-norm leads to sparse solutions. To control sparseness of solutions, we propose to use an internal division of the l sub 2-norm and pointwise normalized l sub 1-norm. The optimization problem constructed as above can be recast as a second-order cone program SOCP, a nonlinear convex problem. The problem can be solved using recently developed efficient interior-point methods, Computer simulations showed that the sparseness of estimators obtained with the proposed method reflects both the ratio of internal division and the sparseness of true sources. Regularization of normalization and relaxation of constraint conditions in the presence of noise are also presented,

Subject Categories:

  • Medicine and Medical Research
  • Statistics and Probability

Distribution Statement:

APPROVED FOR PUBLIC RELEASE