Toward ideal imaging equipment
    At the State University of New York in Stony Brook, Assistant Professor Emilia Entcheva and her graduate student, Harold Bien, regularly perform fluorescence imaging to monitor dynamic events in cell cultures, and they have reviewed imaging equipment and offer suggestions for its improvement.
    Imaging multiple cells simultaneously requires a large working distance, but most currently available objectives that offer a large working distance have a low numerical aperture. Therefore, they do not gather light well and have a lower spatial resolution. Using large-diameter lenses, a tandem-lens assembly and contact fluorescence imaging can compensate for the lack of adequate objectives, but none of these are perfect solutions.
   The reviewers wrote that the detector is the most important part of the optical setup. For cell culture imaging, photodiode array detectors are most widely used because they offer good temporal resolution and a good signal-to-noise ratio. However, they have a low spatial resolution. CCDs tend to provide high spatial or temporal resolution, but not both. While CMOS detectors offer rapid detection but lower resolution, they are becoming popular and are rapidly developing. Therefore, their resolution could improve. The authors were most excited by electron-multiplication CCDs because they offer fast imaging at low light levels.
   Imaging results in large amounts of computer information that is difficult to process in real-time. This problem can be partially solved with additional memory, a bus with a high data transfer rate, protocols that enable rapid writing to the hard drive, as well as a fast camera-to-computer interface known as a frame grabber. However, the authors note that the ability of peripherals to process data may be the greatest limiting factor for real-time data recording and call for improvements such as better signal processing algorithms and greater memory. (Progress in Biophysics and Molecular Biology, October 2006, pp. 232-257.)