Alternative X-ray filters for an intra-oral digital radiographic system

摘要

Objective: The aim of this study was to evaluate the effect of the modulation of the radiation spectrum with the use of alternative X-ray filters in the quality of intra-oral digital images from storage phosphor plates. Methods: The radiographic exposures were performed in a GE 1000 X-ray machine (General Electric Co., Milwaukee, WI), operating at 65kVp, 10mA, 40cm focus receptor distance using three different exposure times: 0.05 s, 0.16 s and 0.35 s. The control filter (GC) was 100% aluminium (Al) with a thickness of 1.5 mm. The tested filters were: G1, 97% Al and 3% copper (Cu) with 1.47mm thickness; G2, 96% Al and 4% Cu with 1.53 mm thickness; G3, 95% Al and 5% zinc (Zn) with 1.56mm thickness; G4, 98% Al and 2% Zn with 1.5 mm thickness; and G5, 95% Cu and 5% Zn with 1.6mm thickness. For formation of the image, a 12-step Al wedge (each step with increments of 1mm in thickness) was radiographed 10 times. Pixel values measured in digital images were converted into optical density (OD). Results: All replicates showed OD with high reproducibility (r > 0.95) for all exposure times and tested filters. In comparison between filters, statistically significant differences in density (p > 0.05) were observed. The OD curve of the G5 filter in all exposure times and G3 filter in an exposure time of 0.05s showed changes in shape (p > 0.05). Conclusions: Excluding the G5 filter, all others tested filters can be used as a substitute for GC without losses in image quality.