Characterizing Scatter Correction Software of 5 Mobile Radiography Units: An Anthropomorphic Phantom Study

Bedside radiographs are usually obtained gridless, without a physical scatter correction grid because of several limitations. Therefore, multiple manufacturers of mobile radiography systems provide the possibility to apply scatter correction software (SC SW) on those images. The purpose of this study was to characterize different series of radiographs-gridless, SC SW, and physical grid-with an image quality assessment algorithm (IQAA). Furthermore, we investigated the potential dose reduction and the correlation between the output of the IQAA and the human observers.

We obtained different series of radiographs with an anthropomorphic phantom (multipurpose chest phantom N1 "Lungman," Kyoto Kagaku, Kyoto, Japan). All radiographs were obtained with flat-panel detectors of 5 different manufacturers in a wall bucky system. An IQAA to analyze the radiographs was implemented in our department but was originally developed by the research group of the Duke University Medical Center. Seven physical quantities were calculated by the IQAA: rib-lung contrast (RLcontrast), subdiaphragm-lung contrast (SLcontrast), lung detail (Ldetail), mediastinum detail (Mdetail), lung noise (Lnoise), mediastinum noise (Mnoise), and rib-lung sharpness (RLsharpness). In a proof of concept, the results of the IQAA were validated by 3 experienced radiologists.

Regression coefficients (b) of the linear regression model indicate that the human observer results correlate well with the IQAA (b ≥ 0.89, R2 ≥ 0.83). All manufacturers have SC SW that increases the 7 physical quantities of the gridless images. However, several manufacturers have SC SW that increases the physical metrics to the same level as the physical grid images. The SC SW radiographs obtained with a reduced tube load have an increased level of contrast, detail, sharpness, and noise compared with the gridless images obtained with the higher tube load.

We have proven in a proof of concept that the originally developed IQAA can be used to characterize different series of images of different manufacturers. Based on the physical quantities, SC SW increases the contrast, detail, sharpness, and noise. The experimental results in this study assume a patient dose reduction could be possible when SC SW is applied.