A CdZnTe slot-scanned detector for digital mammography

A new high-resolution detector has been developed for use in a slot-scanned digital mammography system. The detector is a hybrid device that consists of a CCD operating in time-delay integration mode that is bonded to a 150-μm-thick CdZnTe photoconductor array. The CCD was designed with a detector e...

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Veröffentlicht in:Medical physics (Lancaster) 2002-12, Vol.29 (12), p.2767-2781
Hauptverfasser: Mainprize, James G., Ford, Nancy L., Yin, Shi, Gordon, Eli E., Hamilton, William J., Tümer, Tümay O., Yaffe, Martin J.
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Sprache:eng
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Zusammenfassung:A new high-resolution detector has been developed for use in a slot-scanned digital mammography system. The detector is a hybrid device that consists of a CCD operating in time-delay integration mode that is bonded to a 150-μm-thick CdZnTe photoconductor array. The CCD was designed with a detector element pitch of 50 μm. Two devices were evaluated with differing crystalline quality. Incomplete charge collection was a source of reduction in DQE. This occurs in both devices due to characteristically low mobility-lifetime products for CdZnTe, with the greatest losses demonstrated by the multicrystalline sample. The mobility-lifetime products for the multicrystalline device were found to be 2.4×10 −4 and 4.0×10 −7 cm 2 /V for electrons and holes, respectively. The device constructed with higher quality single crystal CdZnTe demonstrated mobility-lifetime products of 1.0×10 −4 and 4.4×10 −6 cm 2 /V for electrons and holes. The MTF and DQE for the device were measured at several exposures and results were compared to predictions from a linear systems model of signal and noise propagation. The MTF at a spatial frequency of 10 mm −1 exceeded 0.18 and 0.56 along the scan and slot directions, respectively. Scanning motion and CCD design limited the resolution along the scan direction. For an x-ray beam from a tungsten target tube with 40 μm molybdenum filtration operated at 26 kV, the single crystal device demonstrated a DQE(0) of 0.70±0.02 at 7.1×10 −6 C/kg (27 mR) exposure to the detector, despite its relatively poor charge collection efficiency.
ISSN:0094-2405
2473-4209
DOI:10.1118/1.1523932