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Effect of various noise sources on the detective quantum efficiency of phosphor screens
Author(s) -
Nishikawa Robert M.,
Yaffe Martin J.
Publication year - 1990
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 - 10.1118/1.596572
Subject(s) - detective quantum efficiency , quantum noise , physics , noise (video) , optics , optical transfer function , noise power , shot noise , detector , quantum , image quality , quantum mechanics , power (physics) , computer science , artificial intelligence , image (mathematics)
We have examined the effect of screen‐structure, optical‐detector, and secondary‐quantum noise sources on detective quantum efficiency, DQE( f ). This was done by using experimental measurements of screen‐structure and optical‐detector noise in combination with a theoretical model which predicts x‐ray quantum and secondary‐quantum noise for different optical and physical properties of a phosphor screen. The reduction in DQE( f ) from noise sources other than x‐ray quantum noise depends on the noise power spectra (NPS) of these other sources relative to the x‐ray quantum NPS. Even though x‐ray quantum noise may be the dominant noise source at low spatial frequencies, it decreases relatively rapidly with increasing frequency so that other noise sources, which may be small at low frequencies, dominate. Our model predicts that DQE( f ) can be increased, at spatial frequencies <4 mm − 1 , by changing the optical properties of the screen even though modulation transfer function MTF( f ) may decrease. Furthermore, if screen and optical‐detector noise decrease with increasing frequency and secondary‐quantum noise sufficiently small, then DQE( f ) will also be improved at frequencies >4 mm − 1 .