Comparison of different computed radiography systems: physical characterization and contrast detail analysis.
OBJECTIVE
In this study, five different units based on three different technologies-traditional computed radiography (CR) units with granular phosphor and single-side reading, granular phosphor and dual-side reading, and columnar phosphor and line-scanning reading-are compared in terms of physical characterization and contrast detail analysis.


METHODS
The physical characterization of the five systems was obtained with the standard beam condition RQA5. Three of the units have been developed by FUJIFILM (FCR ST-VI, FCR ST-BD, and FCR Velocity U), one by Kodak (Direct View CR 975), and one by Agfa (DX-S). The quantitative comparison is based on the calculation of the modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE). Noise investigation was also achieved by using a relative standard deviation analysis. Psychophysical characterization is assessed by performing a contrast detail analysis with an automatic reading of CDRAD images.


RESULTS
The most advanced units based on columnar phosphors provide MTF values in line or better than those from conventional CR systems. The greater thickness of the columnar phosphor improves the efficiency, allowing for enhanced noise properties. In fact, NPS values for standard CR systems are remarkably higher for all the investigated exposures and especially for frequencies up to 3.5 lp/mm. As a consequence, DQE values for the three units based on columnar phosphors and line-scanning reading, or granular phosphor and dual-side reading, are neatly better than those from conventional CR systems. Actually, DQE values of about 40% are easily achievable for all the investigated exposures.


CONCLUSIONS
This study suggests that systems based on the dual-side reading or line-scanning reading with columnar phosphors provide a remarkable improvement when compared to conventional CR units and yield results in line with those obtained from most digital detectors for radiography.
Servizio Fisica Sanitarìa, Azienda USL di Modena, 41100 Modena, Italy.
Stefano
S
Rivetti
Nico
N
Lanconelli
Marco
M
Bertolini
Andrea
A
Nitrosi
Aldo
A
Burani
Domenico
D
Acchiappati
D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D011856:Radiographic Image Enhancement / Q000295:instrumentation* / Q000379:methods; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity