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Effects of beam collimation on image quality
C A Peterson1, S M Mauriello, V P Overman
1Department of Biostatistics, School of Public Health, University of North Carolina-Chapel Hill, USA.
Purpose:
The purpose of this study was to determine the effect of three film-speed/collimator combinations on image quality, based on reviewer preference and diagnostic quality, based on caries detection.
Method:
Two hundred sixteen proximal surfaces were evaluated for the presence and severity of carious lesions on bitewing-simulated projections using D-speed film/circular, E-speed film/rectangular, and E-speed film/circular collimation. Matched films by model type were ranked, based on reviewer preference. Preference data were analyzed using Friedman's test, while the caries detection data were analyzed using a 3 x 3 x 3 x 6 ANOVA model and the kappa statistic. Variability components of the ANOVA were used to determine inter- and intra-rater reliability.
Results:
Inter- and intra-rater reliability were 90.9 and 98.7%, respectively. Each of the film-speed/collimator combinations had average preference rankings that were significantly different from one another for each criteria (p < 0.001), with E-speed film/rectangular collimation consistently ranking highest and E-speed film/circular collimation consistently ranking lowest. There was excellent agreement in caries detection among the three film-speed/collimator combinations (kw = 0.92, kw = 0.94).
Conclusion:
Results from the subjective comparison indicated that E-speed film with rectangular collimation ranked highest for film resolution, overall appearance, and choice for caries diagnosis, while E-speed film with circular collimation ranked lowest. Caries diagnosis was comparable among the three film-speed/collimator combinations.