RESUMO
Current guidelines quote tolerances for automatic exposure control (AEC) device performance for X-ray systems as 'Baseline ± X %'. However, in the situation where a baseline figure has not yet been achieved, as in the case of commissioning assessments, this tolerance is not relevant. The purpose of this work is to provide mean doses for direct digital radiography (DDR) X-ray system, operating in AEC, against which comparisons can be made. Dose measurements have been recorded under AEC operation on 29 DDR detectors from three different manufacturers. Two different testing protocols were examined: (1) water equivalent phantoms in front of the DDR detector and (2) aluminium block at the tube head. The average patient exit dose, using the aluminium block was 4.6 µGy with the antiscatter grid in place and 4.0 µGy with the grid removed. Using the water phantoms, the average dose was measured at 17.1 µGy with the antiscatter grid in place and 5.4 µGy with grid removed. Based on these results, it is clear that different testing configurations significantly impact on the measured dose.
