Systematic development of input-quantum-limited fluoroscopic imagers based on active matrix, flat-panel technology

Larry E. Antonuk, Qihua Zhao, Zhong Su, Jin Yamamoto, Youcef El-Mohri, Yixin Li, Yi Wang, Amit Sawant

Research output: Chapter in Book/Report/Conference proceedingConference contribution

13 Scopus citations


The development of fluoroscopic imagers exhibiting performance that is primarily limited by the noise of the incident x-ray quanta, even at very low exposures, remains a highly desirable objective for active matrix flat-panel technology. Previous theoretical and empirical studies have indicated that promising strategies to achieving this goal include the development of array designs incorporating improved optical collection fill factors, pixel-level amplifiers, or very high-gain photoconductors. Our group is pursuing all three strategies and this paper describes progress toward the systematic development of array designs involving the last approach. The research involved the iterative fabrication and evaluation of a series of prototype imagers incorporating a promising high-gain photoconductive material, mercuric iodide (HgI 2). Over many cycles of photoconductor deposition and array evaluation, improvements in a variety of properties have been observed and remaining fundamental challenges have become apparent. For example, process compatibility between the deposited HgI 2 and the arrays has been greatly improved, while preserving efficient, prompt signal extraction. As a result, x-ray sensitivities within a factor of two of the nominal limit associated with the single-crystal form of HgI 2 have been observed at relatively low electric fields (-0.1 to 0.6 V/μm), for some iterations. In addition, for a number of iterations, performance targets for dark current stability and range of linearity have been met or exceeded. However, spotting of the array, due to localized chemical reactions, is still a concern. Moreover, the dark current, uniformity of pixel response, and degree of charge trapping, though markedly improved for some iterations, require further optimization. Furthermore, achieving the desired performance for all properties simultaneously remains an important goal. In this paper, a broad overview of the progress of the research will be presented, remaining challenges in the development of this photoconductive material will be outlined, and prospects for further improvement will be discussed.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
EditorsM.J. Yaffe, M.J. Flynn
Number of pages12
StatePublished - 2004
EventMedical Imaging 2004: Physics of Medical Imaging - San Diego, CA, United States
Duration: Feb 15 2004Feb 17 2004


OtherMedical Imaging 2004: Physics of Medical Imaging
Country/TerritoryUnited States
CitySan Diego, CA


  • Active matrix flat-panel imager
  • Cascaded systems modeling
  • Digital fluoroscopy
  • Digital radiography
  • Direct detection
  • Indirect detection

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Condensed Matter Physics


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