TY - JOUR
T1 - Asymptotic SNR of scalar and vector minimum-variance beanformers for neuromagnetic source reconstruction
AU - Sekihara, Kensuke
AU - Nagarajan, Srikantan S.
AU - Poeppel, David
AU - Marantz, Alec
N1 - Funding Information:
Manuscript received July 9, 2003; revised December 21, 2003. The work of K. Sekihara was supported by Grants-in-Aid from the Ministry of Education, Science, Culture and Sports in Japan (C13680948 and C16500296).. The work of S. S. Nagarajan was supported by the Whitaker Foundation and by the National Institute of Health (P41RR12553-03 and R01-DC004855-01A1). The work of D. Poeppel was supported by the National Institute of Health (NIH-R01-DC5660). Asterisk indicates corresponding author. *K. Sekihara is with the Department of Electronic Systems and Engineering, Tokyo Metropolitan Institute of Technology, Tokyo 191-0065, Japan (e-mail: ksekiha@cc.tmit.ac.jp).
PY - 2004/10
Y1 - 2004/10
N2 - To reconstruct neuromagnetic sources, the minimum-variance, beamformer has been extended to incorporate the three-dimensional vector nature of the sources, and two types of extensions-the scalar- and vector-type extensions-have been proposed. This paper discusses the asymptotic signal-to-noise ratio (SNR) of the outputs of these two types of beamformers. We first show that these two types of beamformers give exactly the same output power and output SNR if the beamformer pointing direction is optimized. We then compare the output SNR of the beamformer with optimum direction to that of the conventional vector beamformer formulation where the beamformer pointing direction is not optimized. The comparison shows that the beamformer with optimum direction gives an output SNR superior to that of the conventional vector beamformer. Numerical examples validating the results of the analysis are presented.
AB - To reconstruct neuromagnetic sources, the minimum-variance, beamformer has been extended to incorporate the three-dimensional vector nature of the sources, and two types of extensions-the scalar- and vector-type extensions-have been proposed. This paper discusses the asymptotic signal-to-noise ratio (SNR) of the outputs of these two types of beamformers. We first show that these two types of beamformers give exactly the same output power and output SNR if the beamformer pointing direction is optimized. We then compare the output SNR of the beamformer with optimum direction to that of the conventional vector beamformer formulation where the beamformer pointing direction is not optimized. The comparison shows that the beamformer with optimum direction gives an output SNR superior to that of the conventional vector beamformer. Numerical examples validating the results of the analysis are presented.
KW - Biomagnetism
KW - Inverse problems
KW - Magnetoencephalography
KW - Minimum-variance beamformer
KW - Neural signal processing
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U2 - 10.1109/TBME.2004.827926
DO - 10.1109/TBME.2004.827926
M3 - Article
C2 - 15490820
AN - SCOPUS:4644331980
SN - 0018-9294
VL - 51
SP - 1726
EP - 1734
JO - IRE transactions on medical electronics
JF - IRE transactions on medical electronics
IS - 10
ER -