An examination of automatic exposure control regimes for two digital radiography systems

摘要: The influence of two methods an automatic exposure control (AEC) setup using a simple measure detectability is examined as function x-ray beam quality for computed radiography (CR) system and indirect conversion digital (DR) system. regimes assessed were constant air kerma at the detector contrast noise ratio (CNR). A low scatter geometry was employed with spectra varying from 60 kV 1 mm Cu to 125 2 Cu. CNR measured thick Al square dimension cm by cm. Detectability quantified via nominal fixed 70 added filtration, taken c-d curves Leeds TO20 test object, four spectra. In addition, objective image parameters including modulation transfer (MTF), power spectrum (NPS) detective quantum efficiency (DQE) also both systems different It found that strategy did not maintain threshold (simple detectability) mean energy increased, either CR or DR For detector, disc increased factor 4.4 3.50% 15.4% tube potential raised kV, while 3.4, 2.27% 7.67% 120 kV. method more successful maintaining discs. changed 1.2, 4.80% 5.70% system, 5.66% (a 1.4 increase). required increase in factors 14.5 4.5 detectors, respectively. Rose SNR used show should be modulated inverse loss squared reduction frequency DQE order constant. Calculations SNR, made extrapolated DQE(0), within 25% detectors. These results suggest keeps object increasing overcome (a) (b) photon loss, due increased. AEC set up hold nearly will level contrast-detail changes. considerably if qualities.