Informace o publikaci
New Recording Setup for Ratiometric Recording of Action Potentials By Optical Means
| Název česky | Nové měřící zařízení pro ratiometrický záznam akčních potenciálů optickou metodou |
|---|---|
| Autoři | |
| Rok publikování | 2008 |
| Druh | Článek ve sborníku |
| Konference | Computers in Cardiology |
| Fakulta / Pracoviště MU | |
| Citace | |
| Obor | Fyziologie |
| Klíčová slova | optical method;action potential;ratiometry;voltage sensitive dye |
| Popis | The monophasic action potential (MAP) can be recorded from the heart surface by optical way via fluorescence measurement. Common fluorescence method is based on usage of voltage-sensitive dye (VSD), usually di-4-ANEPPS. VSD undergoes changes in its electronic structure, and consequently its fluorescence spectra, in response to changes in the surrounding electric field. As the VSD emission spectra shifts with the electric field, MAP can is represented by measurement in a specific wavelength band. The main drawback of the method is large motion artefact present in MAP recordings caused by relative movement of optical probe with the heart surface. Another method of fluorescence measurement is ratiometric and takes the advantage of the emission spectra shift depending on cell membrane potential. The method is based on measurements at two different wavelengths or two narrow wavelength bands located left and right from the center of emission spectrum. The emitted light is split into two beams by a dichroic mirror. Light is detected by photodiodes for both beams separately and MAP signal is computed as a ratio of these two signals. Motion artefacts presented in both optical signals are divided and thus suppressed. The proposed method for modified ratiometric measurements exploits newly available segmented narrow-band photodiodes. They consists of two sensors in a single package, each of them sensitive in non-overlapping wavelength bands. Thus, a beam splitter which attenuates the emitted light is replaced. Six isolated New Zealand rabbit hearts were investigated in Langendorff setup. Three hearts were studied using a common ratiometric fluorescence setup with a beam splitter. The other three hearts were studied using a proposed system with a segmented light sensor. Each experiment consisted of four phases: control period, staining of the dye, dye washout and MAP recording. Conditions for all experiments were kept same (surrounding scattered light, electrical shielding). Signal-to-noise ratio (SNR) was evaluated for each MAP signal. The average SNR for the common ratiometric system was SNR=20dB. The proposed system consistently allowed get SNR>60dB. The ratiometric fluorescence method based on detection of emitted light by a segment narrow-band photodiode was proposed and built up. The results show a higher sensitivity of the recording system quantified in getting higher signal-to-noise ratio. Further, the new system is more compact and resistant to mechanical damage and vibrations comparing to common ratiometric fluorescence setup. |