Computer aided detection helps radiologists to detect pulmonary nodules in chest radiographs, when having bone suppressed images available

S. Schalekamp, B. van Ginneken, E. Koedam, L. Quekel, M. Snoeren, R. Wittenberg, N. Karssemeijer and C. Schaefer-Prokop

in: Annual Meeting of the Radiological Society of North America, 2012

Abstract

PURPOSE. Studies evaluating the effects of computer aided detection (CAD) to support radiologists in the detection of pulmonary nodules in chest radiographs (CXR) described the radiologists? difficulties to discriminate from false positive candidates. We investigated the effect of an improved CAD system on nodule detection performance in CXR with the additional availability of bone suppression images (BSI). METHOD AND MATERIALS. Five radiologists and 3 residents served as observers and were asked to separately score location and confidence score for the detection of nodules in CXR without (mode A) and with the availability of CAD candidates (mode B). The study group consisted of 108 PA and lateral CXRs with a CT proven solitary pulmonary nodule and 192 age-matched CT proven negative controls. For both reading modes readers had BSI available. CAD marks and BSI were created by a commercially available software package (ClearRead +Detect 5.2, formerly Onguard 5.2; ClearRead Bone Suppression 2.4, formerly Softview 2.4, Riverain Medical, Miamisburg, Ohio). Multi reader multi case (MRMC) Receiver operating characteristics (ROC) were used for statistical analysis: partial area under the curve, at a specificity interval of 80-100% served as figure of merit. RESULTS. Average nodule size was 17.5mm (7-36mm), with a malignancy rate of 83%. Standalone CAD performance was 74% with 1.0 FP/image. Observer performance significantly increased with the use of CAD and outperformed CXR with use of BSI (p=0.047). Mean sensitivity of the observers was 74% with 0.25 FP/image without CAD and 80% with 0.33 FP/image with CAD. Operating at a specificity of 90%, lung nodule detection sensitivity increased from 70.3% with CXR and BSI to 73.0% with additional availability of CAD. On average 10.5% of all true positive CAD marks were rejected by the radiologists, indicating potential for further improvement with the use of CAD. CONCLUSION. Even with bone suppressed images available, computer aided detection shows additional value in lung nodule detection for radiologists.