Direct method for reconstruction of multiple equivalent current dipoles

Nara, Takaaki; Oohama, Junji; Ando, Shigeru; Takeda, Tsunehiro

doi:10.1016/j.ics.2006.12.080

Cited by 1 publication

(3 citation statements)

References 7 publications

(13 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“….) appears in many inverse problems such as computed tomography (CT) (Golub et al 2000), EEG inversion (El-Badia and Ha-Duong 2000, Nara and Ando 2003), radial MEG inversion with a spherically symmetric head model (Nara et al 2007) and locating the zeros of analytic functions (Kravanja et al 1999). We call it the 'moment problem' in this paper.…”

Section: Moment Problem For Sphericalmentioning

confidence: 99%

“…Contrarily, in the parametric modeling approach, the current sources are represented by several isolated dipoles with unknown positions and moments. These parameters are reconstructed by nonlinear leastsquares fitting (Huang et al 1998, Uutela et al 1998, by the scanning method (Mosher et al 1992, Mosher and Leahy 1998, van Veen et al 1997 and even by exact algebraic methods which can reconstruct the dipole parameters directly from the data (Ohe and Ohnaka 1994, El-Badia and Ha-Duong 2000, Yamatani et al 2002, Nara and Ando 2003, Nara et al 2004, 2007. By virtue of the descriptiveness of the parametric modeling, the results of these methods can be less ambiguous and more accurate.…”

Section: Introductionmentioning

confidence: 99%

“…A problem of the direct algebraic methods is, however, in the applicable mathematical conditions. They have been restricted to the inversion using EEG data only (Ohe and Ohnaka 1994, El-Badia and Ha-Duong 2000, Nara and Ando 2003 or radial MEG data only with a spherically symmetric head model (Yamatani et al 2002, Nara et al 2007 in spite of the growing demand for obtaining a rapid guess of dominant sources, both for real time monitoring and as the initial values of the nonlinear dipolar or multipolar fitting for the patch sources (Jerbi et al 2004). Hence this kind of algorithm is still the subject of active study that is of both theoretical and practical importance.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Direct reconstruction algorithm of current dipoles for vector magnetoencephalography and electroencephalography

et al. 2007

View full text Add to dashboard Cite

This paper presents a novel algorithm to reconstruct parameters of a sufficient number of current dipoles that describe data (equivalent current dipoles, ECDs, hereafter) from radial/vector magnetoencephalography (MEG) with and without electroencephalography (EEG). We assume a three-compartment head model and arbitrary surfaces on which the MEG sensors and EEG electrodes are placed. Via the multipole expansion of the magnetic field, we obtain algebraic equations relating the dipole parameters to the vector MEG/EEG data. By solving them directly, without providing initial parameter guesses and computing forward solutions iteratively, the dipole positions and moments projected onto the xy-plane (equatorial plane) are reconstructed from a single time shot of the data. In addition, when the head layers and the sensor surfaces are spherically symmetric, we show that the required data reduce to radial MEG only. This clarifies the advantage of vector MEG/EEG measurements and algorithms for a generally-shaped head and sensor surfaces. In the numerical simulations, the centroids of the patch sources are well localized using vector/radial MEG measured on the upper hemisphere. By assuming the model order to be larger than the actual dipole number, the resultant spurious dipole is shown to have a much smaller strength magnetic moment (about 0.05 times smaller when the SNR = 16 dB), so that the number of ECDs is reasonably estimated. We consider that our direct method with greatly reduced computational cost can also be used to provide a good initial guess for conventional dipolar/multipolar fitting algorithms.

show abstract