Bone suppressed images improve pulmonary fungal infection detection in chest radiographs

S. Schalekamp, I. van den Berk, I. Hartmann, M. Snoeren, A. Odink, S. Pegge, L. Schijf, N. Karssemeijer and C. Schaefer-Prokop

European Congress of Radiology 2014.

Purpose: To assess the effect of bone suppression images on observer performance in detecting pulmonary fungal infections (PFI) on chest radiographs. Materials and Methods: 105 frontal (bedside or PA) chest radiographs (CXR) of suspects for PFI were collected from four institutions. Presence or absence of disease was determined by an expert radiologist and a clinical researcher in consensus, using CT as reference standard. Radiographs could contain single or multiple sites of infection, and were classified into four categories of subtlety. Bone suppressed images (BSI) were generated by ClearRead BSI 3.2 (Riverain Technologies, Ohio). Five radiologists and two residents participated in an observer study. Evaluation was done on a per lung basis, resulting in 78 diseased lungs and 132 normal lungs. Observers scored the lungs on a continuous scale (0-100), and marked the most suspicious lesion, if present. Area under the ROC curve (AUC) served as performance measure. P-values were calculated using the Dorfman-Berbaum-Metz method. Sensitivity and specificity were calculated considering only the lungs with a suspiciousness score over 50 to be positive. Results: AUC without BSI was 0.815, and increased to 0.853 with BSI (p=0.01). Six of the seven observers increased their performance, four of them significantly. Sensitivity increased from 49% to 66%. Specificity dropped from 95% to 90%. Significant improvement of performance was seen in the group of very subtle cases (p<0.001). Conclusion: BSI significantly improved detection performance of PFI in chest radiographs, especially for very subtle abnormalities. BSI improved the sensitivity of the CXR examination, outweighing the smaller loss in specificity.