Biomedical subjects

C E Davila

Publications and source records attributed to C E Davila.

5 recordsLinked to original sources

PubMed2000

Subspace averaging of steady-state visual evoked potentials.

A new algorithm for doing signal averaging of steady-state visual evoked potentials (VEP's) is described. The subspace average is obtained by finding the orthogonal projection of the VEP measurement vector onto the signal subspace, which is based on a sinusoidal VEP signal model. The subspace average is seen to out-perform the conventional average using a new signal-to-noise-ratio-based performance measure on simulated and actual VEP data.

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PubMed1998

Optimal detection of visual evoked potentials.

We consider the problem of detecting visual evoked potentials (VEP's). A matched subspace filter is applied to the detection of the VEP and is demonstrated to perform better than a number of other evoked potential detectors. Unlike single-harmonic detectors, the matched subspace filter (MSF) detector is suitable for detecting multiharmonic VEP's. Moreover, the MSF is optimal in the uniformly most powerful sense for multiharmonic signals with unknown noise variance.

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PubMed1994

Estimation of single sweep steady-state visual evoked potentials by adaptive line enhancement.

An adaptive line enhancer (ALE) is used to obtain estimates of the single sweep steady-state visual evoked potential (SSVEP). The method is seen to enhance the estimated signal-to-noise ratio of the single sweep SSVEP by as much as 10 dB.

Algorithms↗

PubMed1993

RadioVisioGraphy of the temporomandibular joint: comparisons with transcranial radiography.

RadioVisioGraphy (RVG), a new digital imaging technique, is compared to conventional transcranial radiographic imaging of the temporomandibular joint. The results of this study using fixed human cadaver specimens revealed an excellent correlation between the recorded images and the actual anatomic specimens. Dosimetry, using a beryllium-windowed ionization chamber, showed a 64% dose reduction with charge-coupled device (CCD) when compared to standard film-screen combination.

Aged↗

PubMed1992

Weighted averaging of evoked potentials.

Weighted averages of brain evoked potentials (EP's) are obtained by weighting each single EP sweep prior to averaging. These weights are shown to maximize the signal-to-noise ratio (SNR) of the resulting average if they satisfy a generalized eigenvalue problem involving the correlation matrices of the underlying signal and noise components. The signal and noise correlation matrices are difficult to estimate and the solution of the generalized eigenvalue problem is often computationally impractical for real-time processing. Correspondingly, a number of simplifying assumptions about the signal and noise correlation matrices are made which allow an efficient method of approximating the maximum SNR weights. Experimental results are given using actual auditory EP data which demonstrate that the resulting weighted average has estimated SNR's that are up to 21% greater than the conventional ensemble average SNR.

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