Evaluation of the Effective Detective Quantum Efficiency for Various Tube Voltages with Digital Radiography for Chest Imaging

摘要

The concept of effective detective quantum efficiency (eDQE) has recently been developed and introduced. The purpose of this study was to use the eDQE to evaluate the effect of tube voltage and grid for chest imaging with a direct flat-panel-based digital radiographic system. The exposure factors that we considered were the tube potential and an anti-scatter moving grid. The incident air kerma was adjusted for each tube potential to yield an effective dose of 34 μSv. The scatter fraction (SF), transmission fraction (TF), effective modulation transfer function (eMTF), and effective normalized noise power spectrum (eNNPS) were measured using a phantom that simulate the attenuation and scatter properties of the human chest. Our results showed that the resolution properties measured by using eMTFs were independent of the tube potential regardless of whether or not a grid was used. The noise properties through the phantom were greater with the use of an anti-scatter grid than without while the eDQE was largest at a lower tube potential, which we tested without a grid. In conclusion, we measured a high efficiency at a low tube potential without an anti-scatter grid for digital radiography (DR) in chest imaging. The eDQE reflected the real exam environment better than the general DQE because it better reflected the effect of the total X-ray system.