Microprocessor-controlled laser scanner system for multiwavelength cardiac optical mapping

We developed a new laser scanner system that is capable of recording fluorescence spectra at a rapid rate (1 kHz) from 128 laser spots on the heart. The recording of multiple wavelength bands allow the use of emission ratiometry to reduce the motion artifact. Original laser scanners were built with control circuitry external to the computer to obtain sufficient speed. Our system eliminates external circuitry by using a 160 MHz microprocessor that controls deflection of the laser beam by Bragg cells and real-time sampling of fluorescence. Trials were done with six rabbit hearts. Two photomultiplier tubes (PMTs) with a beam splitter sampled green and red fluorescence at 510-570 nm and >590 nm. Simultaneously, two additional digitizers sampled the laser intensity and stimulation current. As many as eight PMTs may be used to record spectra with greater detail. Sufficient dF/F resolution was obtained to study action potentials.