title: Phase shifting prior to spatial filtering enhances optical recordings of cardiac action potential propagation.
abstract: Optical imaging of cardiac electrical activity using a voltage-sensitive dye 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 recorded using a CCD camera. The method is based on the observation that within a small neighborhood of adjacent pixels, the morphology of the optical action potential varies little except for a phase shift in time resulting from the propagation of the wavefront. The method uses a phase-correlation technique 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 domain. The image-processing scheme allows for more accurate extraction of maps of electrical activation, repolarization, and action potential duration.
authors.affiliation: Department of Bioengineering, University of California San Diego, La Jolla 92093-0412, USA.
authors.forename: D
authors.initials: D
authors.lastname: Sung
authors.lastname: Cosman JSJP
authors.forename: R
authors.initials: R
authors.lastname: Mills
authors.forename: A D
authors.initials: AD
authors.lastname: McCulloch
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D005456:Fluorescent Dyes; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D066298:In Vitro Techniques; D008955:Models, Cardiovascular; D010496:Pericardium / Q000502:physiology; D011726:Pyridinium Compounds / Q000032:analysis; D011817:Rabbits; D012815:Signal Processing, Computer-Assisted
chemical_list: D005456:Fluorescent Dyes; D011726:Pyridinium Compounds; C050019:1-(3-sulfonatopropyl)-4-(beta)(2-(di-n-butylamino)-6-naphthylvinyl)pyridinium betaine