Gallery of images.

NewsEtc, August, 1998. Steven Jacques, Oregon Medical Laser Center

This month we emphasize fluorescence lifetime imaging.

The purposes of this gallery are:

  • to provide images that portray our field of biomedical optics and medical lasers.
  • to point interested viewers toward sites that report their development of optical technologies for medicine.
  • to encourage the many other labs doing research in this field to post some images illustrating their work so that the general surfing audience can view our collective progress.

    Fluorescence lifetime imaging creates images on the basis of how long fluorescence persists once a fluorophore is excited. Two approaches toward lifetime measurements are possible:

    The above measurements can be analyzed to reconstruct the internal spatial distribution of fluorescence lifetime and fluorescence yield.

    Imaging a shock wave generated by high pressure nozzle.

    The images compare time-resolved and fluorescence lifetime imaging.
    shock wave

    Shock wave imaged with time resolved camera and pressure sensitive paint. (A) intensity map (arbitrary units).(B) lifetime map (nanoseconds).

    Courtesy of Dr. Ram Levy, McDonnell-Douglas Research Laboratories. Image posted by Laboratory for Fluorescence Dynamics at the University of Illinois at Urbana-Champaign (Enrico Gratton) at link.

    Mapping fluorescence yield in a turbid medium.

    fluorescence yield map

    A reconstructed spatial map of fluorescence yield, on a two-dimensional, 33 x 33 grid. The object locations and sizes are recovered correctly.
    Image posted by The Photon Migration Laboratory, School of Chemical Engineering, Purdue University (Eva Sevick) at link.

    The computer simulated the optics of two fluorescent objects within a turbid medium. The computer simulated frequency-domain measurements of fluorescence at the boundaries. Finally, the computer reconstructed the internal map of fluorescence lifetime and yield. This image shows the map of fluorescence yield, and is NOT a lifetime image.

    Time-resolved measurement of fluorescence lifetime.

    time-resolved lifetime
    Time-resolved measurement of fluorescence lifetime. Two fluorophores are compared, one with a short fluorescence lifetime and one with a long lifetime.
    Image posted by Regensburg University, Institute of Analytical Chemistry, Chemo- and Biosensors (Otto Wolfbeis) at link, and the center's home page is at Regensburg Univ..

    Frequency-domain measurement of fluorescence lifetime

    phase and modulation vs frequency

    The phase and modulation of fluorescence are plotted as functions of the modulation frequency of the excitation source. As the frequency increases beyond the ability of the fluorophore to respond, i.e., when the fluorophore lifetime is long compared to the time period of source modulation, then the modulation decreases. As the frequency increases, phase increases because more cycles can distribute along the average photon path between source and detector. In this example, the midpoint frequency is about 100 MHz.
    Image posted by The Center for Fluorescence Spectroscopy (Joseph Lakowicz) at link, and the center's home page is at CFS.

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