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

The measurement of cardiac transmembrane potential changes with voltag e sensitive dyes is in increasing use. Detection of these very small f luorescent alterations using large multiplexed arrays, such as charge coupled device (CCD) cameras at high sampling rates, has proven challe nging 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, wi th the inevitable consequence of diminishing the fluorescence that is generated. State-of-the-art high frame rate CCD cameras have read nois e levels in the 5-10 e(-) rms range, which is at least two orders of m agnitude above that required to detect voltage sensitive dye alteratio ns at individual pixels corresponding to 1 mm(2) heart regions illumin ated with levels of 100 mW/cm(2) at frame rates approaching 1000 frame s/sec. Image intensification is thus required prior to photon quantifi cation. We report here the development of such a data acquisition syst em using commercially available hardware. Additionally, in the past te n 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 spatial ly adaptive filters based on wavelet denoising of individual pixels to significantly reduce the multiple noise sources present in the acquir ed data. (C) 1998 American Institute of Physics.