D. Sung et al., Phase shifting prior to spatial filtering enhances optical recordings of cardiac action potential propagation, ANN BIOMED, 29(10), 2001, pp. 854-861
Optical imaging of cardiac electrical activity using a voltage-sensitive dy
e provides high spatial resolution maps of action potential propagation and
repolarization. Charge-coupled-device (CCD) camera-based imaging systems,
however, are limited by their low signal-to-noise ratio. We have developed
an image processing method to enhance the quality of optical signals record
ed using a CCD camera. The- method is based on the observation that within
a small neighborhood of adjacent pixels, the morphology of the optical acti
on potential varies little except for a phase shift in time resulting from
the propagation of the wavefront. The method uses a phase-correlation techn
ique to first correct for this time shift before spatially filtering with a
5 X 5 Gaussian convolution kernel (sigma =1.179). A length 5 median filter
is then applied to further reduce noise by filtering in the temporal domai
n. The image-processing scheme allows for more accurate extraction of maps
of electrical activation, repolarization, and action potential duration. (C
) 2001 Biomedical Engineering Society.