title: Quality assessment of confocal microscopy slide-based systems: instability.
abstract: BACKGROUND
  All slide-based fluorescence cytometry detections systems basically include an excitation light source, intermediate optics, and a detection device (CCD or PMT). Occasionally, this equipment becomes unstable, generating unreliable and inferior data.
  
  
  METHODS
  A number of tests have been devised to evaluate equipment performance and instability. The following four instability tests are described: galvanometer scanning, stage drift, correct wavelength spectral detection, and long-term laser power.
  
  
  RESULTS
  Quality assurance tests revealed that a confocal microscope can become unstable in the following parameters, yielding inaccurate data: laser power, PMTs functionality, spectrophotometer accuracy, galvanometer scanning and laser stability, and stage drift. Long-term laser power stability has been observed to vary greatly.
  
  
  CONCLUSIONS
  Confocal systems can become unstable in the following parameters: long-term laser power, galvanometer scanning, spectrophotometer accuracy, and stage stability. Instability in any of these parameters will affect image quality. Laser power fluctuations result from either a defective Acousto-optic tunable filter or improper heat dissipation. Spectrophotometer instability will generate unreliable spectra data, extra light reflections, and poor image quality. Galvanometer scanning instability yields poor image quality while microscope stage drift results in a sample going out of the plane of focus. With minor modifications, these tests may be applicable to other slide-based systems.
authors.affiliation: Reproductive Toxicology Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, US Environmental Protection Agency, Research Triangle Park, NC 27711, USA. zucker.robert@epa.gov
authors.forename: Robert M
authors.initials: RM
authors.lastname: Zucker
mesh_terms: D000818:Animals; D002138:Calibration; D002417:Cattle; D005336:Fiber Optic Technology / Q000295:instrumentation / Q000379:methods / Q000592:standards; D006358:Hot Temperature; D018613:Microscopy, Confocal / Q000295:instrumentation* / Q000379:methods / Q000592:standards*; D013053:Spectrophotometry / Q000295:instrumentation / Q000379:methods / Q000592:standards