| Περίληψη: | The X-ray projective imaging has been evolving rapidly over the last fifteen years, especially after the advent of digitized and digital imaging systems. These systems are constantly gaining ground over older film-screen systems, which tend to be eliminated from clinical environments. The advantages of digitized and digital systems include the speed of each examination, the wide range of exposure, the reduction of repetitions, the possibility of digital storage, archiving and sharing of the medical image, as well as the possibility of post-processing of the final digital X-ray. In addition, depending on the material of each detector, some image quality characteristics, such as spatial resolution, contrast, relative contrast, signal-to-noise ratio, have been significantly improved compared to analogue systems.
The purpose of this study was to evaluate whether the type of detector can influence the image quality on knee X-rays. Three different detectors were compared: a Computed Radiography (CR) detective system, a Digital Radiography (DR) flat panel of caesium iodine scintillator and a Digital Radiography (DR) flat panel of gadolinium oxulfide. The study was performed on lateral knee X-rays and the same exposure factors (55kVp and 5mAs) were used in all radiographies.
Fifteen patients were studied for each detective system (45 in total) and a quantitative analysis was performed. Regions of Interest (ROIs) were manually placed in specific anatomical structures (compact bone, bone marrow, sub-patellar/Hoffa’s fat, patellar ligament, noise in the air and the signal intensity was measured in every region. The statistical analysis was performed using the Analysis Of Variance (ANOVA) method and we compared the results of signal-to-noise ratio, contrast-to-noise ratio and relative contrast for lateral knee radiography. According to the above, we conclude that the DR flat panels and especially the DR of Gd2O2S were superior in SNR and CNR in comparison with the CR cassette. On the other hand, the CR cassette presented better ReCon values in comparison with DR flat panels regarding the tissue-pairs that include the compact bone. These results are due to the different k-edges of each material in the studied detectors, its productivity and its energy matching with the produced X-ray spectrum in that energy.
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