Copper filter for dental radiography: revaluation of radiographic contrast
Palavras-chave:
aluminum, copper, filtration, X-raysResumo
Objective
To study the effects of alternative copper filtration in a dental X-ray machine and evaluate possible changes in radiographic contrast.
Methods
An aluminum step-wedge was radiographed using aluminum (1.5mm) and copper (0.1mm) filters. Physical radiation factors (exposure time, kilovoltage and air-kerma rate) were controlled. After processing, the densitometer readings of the step-wedge step images were measured. For each radiograph, optical density and contrast curves were determined. The values of the areas under the contrast curves for the two groups (aluminum and copper filters) were compareci by the two-tailed Mann-Whitney test, with a levei of significance of O.OS.
Results
The mean areas under the contrast curves were -1.956 and -2.115 for the aluminum and copper filters respectively. According to the statistical test, these values were significantly different: copper filtration yielded better contrast.
Conclusion
The use of copper filter requires longer exposure times; it reduces the air-kerma rate and results in higher contrast values than those obtained with aluminum filter.
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Referências
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