We develop an optical fluorescent mapping system that is able to record the action potential wavefront propagation within cardiac tissue samples with high spatial and temporal resolutions. The system's main component, the fluorescence acquisition device (customized CCD camera), offers a high spatial resolution of 128×128 pixels, with 12-bit digitization and a frame rate of 490 frames/s. The system is designed and implemented to image an area of approximately 20×20 mm at its minimum object distance of 140 mm, corresponding to a spatial resolution of approximately 3 line pairs/mm. Experiments using this system with di-4-ANEPPS-stained canine cardiac tissues with stimulated action potentials through external electrodes result in successful mappings of the distribution and propagation of the action potential wavefronts, showing the system's sensitivity to the change in fluorescence intensity in regions of action potentials. These data demonstrate this optical mapping system as a powerful device in the study of cardiac arrhythmia mechanisms.
An optical fluorescence imaging system was developed using a custom CCD camera. The system is designed and implemented to image an area of 20 mm by 20 mm with a spatial resolution of approximately 3.2 lp/mm. The temporal resolution is 490 frames per second. Comprehensive measurements were performed and the results have shown that the system is capable of providing high spatial resolution while maintaining good temporal resolutions and wide dynamic range. The system is a useful research tool in some biomedical experiments.
A customized dual CCD based optical mapping system is designed and constructed for the purpose of applying ratiometry to the study of cardiac arrhythmia mechanisms. The system offers 490 frames per second data acquisition speed, 128 by 128 detector elements and 12 bits digitization. Each CCD camera is dedicated to imaging a specific
region of the di-4-ANEPPS emission spectrum, through the use of appropriate filtering, the red region (635 ∓ 27.5nm) and the green region (532nm ∓ 19nm). The resulting two dimensional images collected from each spectrum region behaved consistently with the spectrum shift characteristics of di-4-ANEPPS, with the fluorescence intensity of the red region decreasing during action potential and the fluorescence intensity of the green region increasing during action potential. By taking the ratio of the two images, a ratiometric signal is constructed that offered improved uniformity in fluorescence intensity distribution, compared to the individual regional images.
Optical mapping, based on voltage sensitive dyes, has become a prominent technique in the study of electrical activities within cardiac tissues. The technique is best carried out with devices that can gather optical signals with both high spatial frequency and temporal frequency. Currently, two devices dominate the field, Charge Coupled Devices (CCD) and Photo Diode Arrays (PDA). Both optical mapping techniques possess advantages and disadvantages in their performance. The objective of this investigation is to design an optical mapping system with a high spatial resolution CCD as its main component. In this feasibility study, a wavelength selective optical mapping experimental setup was designed and implemented in accordance with the fluorescence characteristics of one of the most common dyes used in cardiac mapping, di-4-ANEPPS. To test the capabilities of the optical system setup, a high resolution (512 pixels by 512 pixels, 12 bit dynamic range) CCD camera with approximately 33 ms temporal resolution is chosen as the fluorescence signal acquisition device. Experiments with di- 4-ANEPPS stained canine cardiac tissues with stimulated action potentials through external electrodes resulted in successful mapping of the distribution and propagation of the action potential wave front. A new CCD based optical mapping system was also built. It offers a 128 by 128 pixel resolution, 12 bits digitization and a temporal resolution of approximately 2 ms.