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Physical characterization of a prototype selenium‐based full field digital mammography detector
Author(s) -
Saunders Robert S.,
Samei Ehsan,
Jesneck Jonathan L.,
Lo Joseph Y.
Publication year - 2005
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 - 10.1118/1.1855033
Subject(s) - detective quantum efficiency , materials science , optics , optical transfer function , tungsten , dot pitch , detector , physics , pixel , image quality , artificial intelligence , computer science , metallurgy , image (mathematics)
The purpose of this study was to measure experimentally the physical performance of a prototype mammographic imager based on a direct detection, flat‐panel array design employing an amorphous selenium converter with 70 μm pixels. The system was characterized for two different anode types, a molybdenum target with molybdenum filtration ( Mo ∕ Mo ) and a tungsten target with rhodium filtration ( W ∕ Rh ) , at two different energies, 28 and 35 kVp, with approximately 2 mm added aluminum filtration. To measure the resolution, the presampled modulation transfer function (MTF) was measured using an edge method. The normalized noise power spectrum (NNPS) was measured by two‐dimensional Fourier analysis of uniformly exposed mammograms. The detective quantum efficiencies (DQEs) were computed from the MTFs, the NNPSs, and theoretical ideal signal to noise ratios. The MTF was found to be close to its ideal limit and reached 0.2 at 11.8mm − 1and 0.1 at 14.1mm − 1for images acquired at an RQA‐M2 technique ( Mo ∕ Mo anode, 28 kVp, 2 mm Al). Using a tungsten technique (MW2; W ∕ Rh anode, 28 kVp, 2 mm Al), the MTF went to 0.2 at 11.2mm − 1and to 0.1 at 13.3mm − 1. The DQE reached a maximum value of 54% at 1.35mm − 1for the RQA‐M2 technique at 1.6 μ C ∕ kg and achieved a peak value of 64% at 1.75mm − 1for the tungsten technique (MW2) at 1.9 μ C ∕ kg . Nevertheless, the DQE showed strong exposure and frequency dependencies. The results indicated that the detector offered high MTFs and DQEs, but structured noise effects may require improved calibration before clinical implementation.