Grey-scale inversion improves detection of lung nodules

Objective The current study aims to establish whether detection of solitary pulmonary nodules can be improved by inverting the grey scale of posteroanterior (PA) chests. Methods 30 PA chest images were presented on 2 occasions to 16 senior radiologists on either primary or secondary class displays in the standard or inverted mode. 15 images within each group contained a single nodule positioned in a range of anatomical sites. A receiver operating characteristic (ROC) methodology was used to explore differences between the presentation modes. Results Improved ROC scores were evident with inverted (Az 0.77) compared with standard (Az 0.73) (p=0.02) images; however, this difference was seen only with the primary displays. The benefits seen are most likely owing to increased nodule luminance with the inverted images, particularly when using primary displays. Conclusion This study demonstrates that the inverted image can offer advantages in lung nodule detection over the standard presentation mode when images are viewed on high-specification viewing systems. The study has demonstrated that there is an improvement in the detectability of lung nodules on an inverted image with a primary display monitor that is not evident with secondary displays. This is likely to be the result of increased nodule luminance on primary displays when images are presented in the inverted mode.