Fast fluorescence lifetime imaging using a full-field homodyne system with applications in biology

A fast, full-field fluorescence lifetime imaging system based on the homodyne technique was built and used for several applications. Also contained herein is the basic theory and background for fluorescence lifetime imaging, as well as data analysis of lifetime distributions. The fast, easy-to-use lifetime imager has proven useful for many applications and essential for several. Examples of applications where such an instrument is needed (and where a conventional system is inadequate) include: any system with large photo-bleaching effects, systems where the intensity changes on the timescale of the measurement, and situations that require real-time display of lifetime images. Measuring photo-porphyrin IX in cells is an example of a system where photo-bleaching makes it difficult to measure. Measuring the lifetime changes in dark adapted plant leaves upon exposure to light is an example of a system with complicated intensity changes. Real-time display of lifetime images is required for clinical work. This paper includes details of the hardware and software for the instrument as well as data taken with the instrument.