CCD MOSAIC DIGITAL MAMMOGRAPHY

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Specific Aims and Hypotheses: The objective of this project is to develop an imaging module for full size digital x-ray mammography. We propose to explore a CCD imaging technique using a novel area-scanning, radiation- shielding mechanism. The concept uses a 6x8 mosaic of CCD imagers. These CCDs are mounted on a carrier platform with gaps between their active areas that are exactly 15 mm in width. The platform is placed under a standard mammographic unit. A lead filter is interposed between the x-ray source and the patient. The lead filter has a mosaic of CCDs and is moved in synchronism with the CCDs. To provide a complete and contiguous image the mosaic will actually be repositioned three times, and a total of four x-ray exposures is made. The unique features of the proposed technique are: large field coverage (18 cm x 24 cm), high spatial resolution (16 lp/mm to 18 lp/mm), scatter rejection and excellent contrast characteristics and lesion detectability under clinical conditions. Methods and Experiments: The proposed imaging concept is unique because its novel optical configuration and scanning-sampling method differs significantly from existing techniques. In order to test our hypotheses, we propose to build a laboratory system to measure modulation transfer function, signal-to-noise ratio, detective quantum efficiency, and lesion detectability. We also propose to conduct phantom studies. Based on our preliminary experiments, a dose efficient, x-ray quantum noise limited system will be achieved using the proposed CCD imaging module. The lesion detectability of this digital mammographic technique is comparable to the gold standard of screen-film technique under the same conditions.