Chest computed radiography imaging parameters for nodule detection: a comparison of image quality and entrance skin dose

Abstract

This study was performed on an anthropomorphic phantom to investigate the performance of three computed radiography (CR) systems with regard to the detection of simulated lung nodules and entrance skin dose. Forty-five chest radiographic images were obtained with three different kVp (100, 110, 120) and five mAs settings (1.0, 2.0, 4.0, 8.0, 10). Image noise, defined as standard deviation (SD) was measured at seven regions of interest and entrance skin dose (ESD) was measured during exposure of each imaging parameter. The mean ESD was measured 0.256 mGy, 0.272 mGy and 0.308 mGy, corresponding to the Afga CR, Kodak CR and Fuji CR systems, respectively. ESD increased significantly with the increase of the kVp and mAs (p<0.001) in the CR systems. SD was significantly different when the mAs were changed (p<0.001), but it was independent of the kVp values (p=0.07-0.30). Up to 40% dose reduction was achieved when kVp was reduced from 120 kVp to 100 kVp, while more than 50% dose reduction could be achieved when mAs were decreased with excellent visualisation of all nodules without compromising image quality. Our results show that radiation dose can be significantly reduced through lowering kVp and mAs without affecting the image quality and visualisation of lung nodules.