A method for visualization of ventricular fibrillation: Design of a cooled fiberoptically coupled image intensified CCD data acquisition system incorporating wavelet shrinkage based adaptive filtering

Francis X. Witkowski, L. Joshua Leon, Patricia A. Penkoske, Robert B. Clark, Mark L. Spano, William L. Ditto, Wayne R. Giles

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

The measurement of cardiac transmembrane potential changes with voltage sensitive dyes is in increasing use. Detection of these very small fluorescent alterations using large multiplexed arrays, such as charge coupled device (CCD) cameras at high sampling rates, has proven challenging and usually requires significant averaging to improve the signal-to-noise ratio. To minimize the damage of living tissue stained with voltage sensitive dyes, excitation photon exposure must be limited, with the inevitable consequence of diminishing the fluorescence that is generated. State-of-the-art high frame rate CCD cameras have read noise levels in the 5-10 e- rms range, which is at least two orders of magnitude above that required to detect voltage sensitive dye alterations at individual pixels corresponding to 1 mm2 heart regions illuminated with levels of 100 mW/cm2 at frame rates approaching 1000 frames/sec. Image intensification is thus required prior to photon quantification. We report here the development of such a data acquisition system using commercially available hardware. Additionally, in the past ten years, a mathematical theory of multiresolution has been developed, and new building blocks called wavelets, allow a signal to be observed at different resolutions. Wavelet analysis also makes possible a new method of extricating signals from noise. We have incorporated spatially adaptive filters based on wavelet denoising of individual pixels to significantly reduce the multiple noise sources present in the acquired data.

Original languageEnglish
Pages (from-to)94-102
Number of pages9
JournalChaos
Volume8
Issue number1
DOIs
StatePublished - Mar 1998

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