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A CdZnTe slot‐scanned detector for digital mammography
Author(s) -
Mainprize James G.,
Ford Nancy L.,
Yin Shi,
Gordon Eli E.,
Hamilton William J.,
Tümer Tümay O.,
Yaffe Martin J.
Publication year - 2002
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1523932
Subject(s) - detective quantum efficiency , optics , materials science , detector , x ray detector , image resolution , digital mammography , image quality , optical transfer function , optoelectronics , physics , mammography , computer science , medicine , breast cancer , image (mathematics) , cancer , artificial intelligence
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 be2.4 × 10− 4and4.0 × 10− 7cm 2/ V for electrons and holes, respectively. The device constructed with higher quality single crystal CdZnTe demonstrated mobility‐lifetime products of1.0 × 10− 4and4.4 × 10− 6cm 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 − 1exceeded 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 at7.1 × 10− 6C/kg (27 mR) exposure to the detector, despite its relatively poor charge collection efficiency.