Stroboscopic excitation fluorescence lifetime imaging

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Fluorescence lifetime imaging (FLIM) is a powerful microscopy technique used widely in biology and medicine particularly for imaging cells. It is based on the use of molecules or proteins that fluoresce when illuminated by a light source. The lifetime of the fluorescence is measured rather than its intensity and so the image created gives information on how long the fluorescence lasts for rather than how bright it is. The lifetime is affected by bio-molecular events and so FLIM provides information on the life cycle of the cell as well as images of it.To measure the fluoresence lifetime a fast detector is usually needed as it only lasts for a few billionths of a second. The duration of the measurement is so short that there is a large uncertainty in the measured value. This research proposes a new technique which uses a stream of light pulses to excite the fluoresence. The fluorescence lifetime is then measured by changing the frequency of these pulses. In this case a slow detector can be used and the lifetime measurement done over many seconds thus removing uncertainties in its value. The technique is similar to the use of a stroboscope to allow the human eye ( a slow detector ) to see rapidly moving objects.