Bone suppression imaging improves observer performance for the detection of lung nodules in chest radiographs

S. Schalekamp, B. van Ginneken, L. Bax, M. Imhof-Tas, L. Meiss, A. Tiehuis, N. Karssemeijer and C. Schaefer-Prokop

Annual Meeting of the Radiological Society of North America 2012.

PURPOSE. Overprojection by osseous structures has been reported in 22 to 95% of missed lung cancer cases as underlying reason for misdiagnosis. Purpose of the study was to assess the effect of bone suppressed imaging on observer performance in detecting lung nodules in chest radiographs. METHOD AND MATERIALS. Posteroanterior and lateral digital chest radiographs of 108 patients with a CT proven solitary nodule, and 192 controls were read by 5 radiologists and 3 residents. Conspicuity of nodules on the radiographs was classified in four categories: obvious (n=32), moderate (n=32), subtle (n=28) and very subtle (n=16). Commercially available software (ClearRead Bone Suppression 2.4, formerly Softview, Riverain Medical, Miamisburg, Ohio) was used to generate bone suppressed images (BSI) of the PA radiographs. Observers read the PA and lateral chest radiographs without and with the availability of BSI. Anatomic locations of suspicion and confidence scores were digitally recorded. Multi reader multi case (MRMC) receiver operating characteristics (ROC) were used for statistical analysis: partial area under the curve using a clinically acceptable specificity between 80 and 100% served as the figure of merit. RESULTS. Average age was 64.8 years for nodule patients and 63.5 years for controls. Average nodule size was 17.5mm (median 17mm). ROC analysis showed improved detection with use of bone suppression imaging compared to chest radiographs alone (p= 0.008). Operating at a specificity of 90%, lung nodule detection sensitivity increased from 67% without BSI to 72% with BSI. Increase of detection performance was highest for moderate and subtle nodules with 11% (66% vs. 73%). Two of 8 nodules that were not reported by any of the observers with CXR alone, were seen by at least 4 observers with BSI.CONCLUSION. Bone suppression imaging improves radiologists? detection performance for pulmonary nodules, in particularly for nodules with intermediate conspicuity.