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Development of High Performance Displays for Mammography

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Final rept. 12 May 1997-12 May 2000

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This research project is concerned with displays for digital mammography. A demountable display tube with its associated vacuum system and electronic control was acquired. It permits investigation of samples of novel cathodo-luminescent materials and their respective substrates with respect to characteristic display performance measures. Work concentrated on CsI as the luminescent material. CsI grows in a fiber like structure, which suggests little lateral light propagation, which could result in high image contrast. CsI samples of different thickness were obtained. The luminescence developed by CsI at 7kV beam electrons is linearly proportional to the beam current and almost linearly proportional to the thickness of the sample. This very important observation suggests that perhaps effects other than just simple cathodoluminescence affect the generation of light when CsI is used as phosphor in a CRT. It is hypothesized that the increased luminance is the result of injected beam electrons causing electroluminescence. These electrons can acquire sufficient energy to cause impact excitation of thallium centers along the length of CsI columns. This important result suggests a means of overcoming a serious deficiency in CRTs, namely inefficient cathodoluminescence and low luminance levels compared to that from the film-light box used in diagnostic radiology.

Subject Categories:

  • Medicine and Medical Research
  • Electrooptical and Optoelectronic Devices

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