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Therapy imaging: A signal‐to‐noise analysis of metal plate/film detectors
Author(s) -
Munro P.,
Rawlinson J. A.,
Fenster A.
Publication year - 1987
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 - 10.1118/1.596114
Subject(s) - detective quantum efficiency , detector , optics , granularity , noise (video) , optical transfer function , materials science , physics , signal to noise ratio (imaging) , signal (programming language) , image resolution , optoelectronics , image quality , computer science , artificial intelligence , image (mathematics) , programming language , operating system
We have measured the modulation transfer functions [MTF ( f )'s] and the noise power spectra [NPS( f )] of therapy x‐ray detectors irradiated by 6 0 Co, 6‐ and 18‐MV radiotherapy beams. Using these quantities, we have calculated the noise‐equivalent quanta [NEQ( f )] and the detective quantum efficiency [DQE( f )] to quantitate the limitations of therapy detectors. The detectors consisted of film or fluorescent screen–film combinations in contact with copper, lead, or tungsten metal plates. The resolution of the detectors was found to be comparable to fluorescent screen–film combinations used in diagnostic radiology, however, the signal‐to‐noise ratio [SNR( f )] of the detectors was limited due to film granularity. We conclude that improved images can be obtained by using alternative detector systems which have less noise or film granularity.