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Technical features of a CCD video camera system to record cardiac fluorescence data
W T Baxter1, J M Davidenko, L M Loew
1Department of Pharmacology, SUNY Health Science Center at Syracuse 13210, USA.
Annals of Biomedical Engineering
|July 1, 1997
Summary
Charge-coupled device (CCD) cameras capture transmembrane activity in heart muscle. While offering high spatial resolution, CCDs can introduce errors in action potential duration (APD) measurements, which can be minimized by using faster frame rates.
Area of Science:
- Biophysics
- Cardiovascular Physiology
- Optical Imaging
Background:
- Voltage-sensitive dyes enable optical recording of transmembrane electrical activity.
- Charge-coupled device (CCD) cameras offer high spatial but limited temporal resolution for imaging.
- Previous imaging systems faced limitations in accurately measuring electrophysiological parameters.
Purpose of the Study:
- To evaluate the utility of CCD cameras for imaging cardiac transmembrane activity.
- To assess the impact of imaging system parameters (blur, noise, frame rate) on electrophysiological measurements.
- To compare optical measurements with traditional microelectrode recordings.
Main Methods:
- Acquisition of transmembrane activity movies from sheep ventricular epicardial muscle using a CCD camera and voltage-sensitive dye.
- Development of a computer model to simulate the effects of imaging parameters on data.
- Simultaneous optical and microelectrode recordings of electrophysiological parameters.
Main Results:
- CCD imaging allowed visualization of propagating waves with good spatial resolution.
- Image noise increased measurement uncertainty, while blur, filtering, and quantization did not systematically affect wave front localization.
- Low frame rates and high cutoff levels led to erroneously long action potential durations (APDs) in optical measurements.
- Optical conduction velocities matched microelectrode recordings, but optical APDs were longer.
Conclusions:
- CCD cameras are suitable for visualizing cardiac electrical activity, but temporal resolution limits accuracy of APD measurements.
- Systematic APD errors can be reduced by optimizing cutoff levels and using the highest possible frame rates.
- Careful consideration of imaging parameters is crucial for accurate electrophysiological measurements using CCD-based optical mapping.