Correlation Coefficient Scanning to Identify Localised Activity
نویسنده
چکیده
In this paper we suggest a method of approaching one biomagnetic modelling problem where subjective judgements are common; the identification of the number and locations of discrete regions of activity. These regions are often modelled as current dipoles. In multi-dipolar systems several different modelling approaches may be adopted. If there is a-priori evidence for a particular set of fixed local generators it is appropriate to use a model comprising a limited number of fixed dipoles of time varying activity [1]. However such a simplification may not be justified. Then there is some difficulty as the full multipledipole inverse problem has poor convergence. In this paper, we describe a method in which a preliminary distributed current solution that has minimal a priori assumptions is subsequently analysed to identify individual dipole patterns. A preliminary algorithm [2] was based on the observation that the distributed current algorithm that we use [3] produces a characteristic extended current image < J > if the source is a dipole. A simple template T, which mimicked this pattern, was scanned over the image to produce a map of the cross-correlation between T and < J >. This algorithm was robust and discriminating. Carrying on from this work, we have improved the template function and have extended the method to three dimensions.
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