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Lag measurement in an a ‐ Se active matrix flat‐panel imager
Author(s) -
Schroeder C.,
Stanescu T.,
Rathee S.,
Fallone B. G.
Publication year - 2004
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 - 10.1118/1.1713298
Subject(s) - optics , residual , active matrix , photon , lag , detector , photon energy , materials science , signal (programming language) , physics , nuclear medicine , electrode , thin film transistor , mathematics , medicine , computer network , algorithm , quantum mechanics , computer science , programming language
Lag and residual contrast have been quantified in an amorphous selenium ( a ‐ Se ) active‐matrix flat‐panel imager (AMFPI) as a function of frame time, kilovoltage (kV) and megavoltage (MV) x‐ray photon energies and amount of radiation incident on the detector. The AMFPI contains a 200 μm thick a ‐ Se layer deposited on a thin film transistor (TFT) array of size 8 . 7 cm × 8.7 cm with an 85‐μm pixel pitch. For all energies, the lag (signal normalized to the signal due to exposure) for the first ( n = 1 ) and second ( n = 2 ) frame after exposure ranges from 0.45% to 0.91% and from 0.29% to 0.51%, respectively. The amount of lag was determined to be a function of the time after the x‐ray exposure irrespective of frame time or the magnitude of exposure. The lag for MV photon energies was slightly less than that for kV photon energies. The residual contrast for all energies studied ranges from 0.41% to 0.75% and from 0.219% to 0.41% for the n = 1 and n = 2 frames, respectively. These results show that lag and residual contrast in kV and MV radiographic applications are always less than 1% for the detection system used and only depend on the time after x‐ray exposure.