Introduction: The quality of a radiograph is based on a good display of structures and is a consequence to good spatial resolution. The computer treatment can add a greater diagnostic usefulness and better quality to the radiographic image. Purpose: We were interested how the exposition conditions and treatment of radiographs influence on their quality and whether the radiographs with the higher signal-to-noise ratio possess better quality to those with the lower ratio. Methods: We have examined some literature and gained radiographs of chest and abdominal organs of a phantom with various levels of blackening. The images were treated with smoothing or improvement of contrast resolution in the ImageJ programme. With the help of three assessors and a new programme intended for such assessment of images, we have gained subjective evaluations of images on the basis of prepared assessment criteria. We have calculated the signal-to-noise ratio of the images in the ImageJ programme. The statistical analysis of data was also performed in order to get results. Results: In the abdominal organs, the statistical analysis ANCOVA has shown the exposition conditions equally influence the quality of image as the contrast improvement and smoothing of images (p=0.189) and differently in untreated images (p<0.001). The same analysis in chest organs established that treatment of images does not statistically significant influence differently on the quality of images (untreated images, p=0.816; smoothing, p=0.641). In abdominal organs in the dependence of the quality of image display to the signal-to-noise ratio and treatment of image with ANOVO, we have calculated there are some differences in the image treatment (p<0.001). The post-hoc tests have shown statistically significant difference between untreated and contrast improved images (p<0.001) and smoothed and contrast improved images (p<0.001). There was no difference between untreated and smoothed images in the signal-to-noise ratio (p=0.068). The same analysis was repeated also in chest organs, where we have calculated that treatment of images does not statistically significant influence on the change of the signal-to-noise ratio (p=0.057). Discussion and conclusion: We have established that treatment does not influence the quality of image display. We have also determined that exposition conditions positively influence on the quality of image display. In original images, the quality increases with the increasing of the signal-to-noise ratio, the quality in the smoothed images remains the same; however, the contrast images show decrease of the quality of image display with the increasing signal-to-noise ratio. In comparison between original and smoothed image, the smoothed is proved better, since the median value is positive. On the other hand, the median value in comparison between the original and contrast images is negative; therefore, the original radiographic image is better.
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