The specific aims of this application would focussed on the development, optimization and quantitative evaluation of a new digital mammography system with the following characteristics: (1) greater than 90 percent quantum absorption efficiency; (2) 15 lp/mm limiting spatial resolution; (3) >5 percent contrast sensitivity; (4) > 80 percent detective quantum efficiency; and (5) 10(4):1 linear dynamic range (> 12 bits contrast resolution). The clinical objective would be to provide substantially improved diagnostic sensitivity for general screening. This new approach is based on: (1) R &D performed by the applicant organization, Nanoptics, Inc., for the Super conducting Super Collider, and (2) front-illuminated, thin-gate CCD technology developed by the Jet Propulsion Laboratory (JPL). The applicants proposed to develop a digital mammography system based on a scanning slot detector, which utilizes a novel plastic scintillating microfiber x-ray converter plate (1 cm x 20 cm x 1 cm thickness). A plastic scintillating fiber plate, whose microfiber axes aligned parallel to the direction of the incident x-ray, provides a superior alternative to phosphor. The applicants described recently having achieved a technological breakthrough in doubling the energy conversion efficiency of our plastic scintillator. In order to increase the x-ray absorption efficiency, the applicants described having successfully incorporated 10 percent by weight of tin into the core of the scintillating microfibers. The applicants described success in using very low refractive index cladding on their microfiber core to increase the light output. Each individual microfiber will be parallax corrected by a thermo-firming process to preserve the inherent high spatial resolution. This process has been successfully developed. The microfibers within which the scintillating light is produced also directly transmit the light to the CCDs. The CCDs are protected from exposure to the x-ray beam by appropriate bends in the 7 cm long continuous microfiber image guide. The CCD has about 50 percent quantum efficiency at blue green region due to the thin-gate technology and has extremely low noise with cooling. The CCDs will be operated in a time-delayed integration mode (TDI) which reduces the x-ray tube loading to an acceptable level and substantially eliminates artifacts in the image. The scanning system also facilitates the acquisition and handling of the large volume of data (155 Mbytes) associated with the high resolution image required for the given image size (8 in x 12 in). The first objective of the proposed research would be to construct a section of slot detector connected to one CCD. This module would be tested extensively to determine all aspects of its performance parameters. Then, the applicants proposed to build one complete prototype slot detector covered by four CCDs including parallel readout of the CCDs. A complete system would be provided to Fischer Imaging for release as a mammography unit to the Moffitt Cancer Center, University of South Florida, to conduct clinical studies and evaluations for further improvement.
