Image analysis was performed using the institutional digital database system (Neusoft V5.5.4.50720). All CT images were reviewed by two radiologists with 5 and 3 years of experience in imaging (Y.F. and W.L.). Imaging was reviewed independently and final decisions reached by consensus. For disagreement between the two primary radiologist interpretations, a third experienced thoracic radiologist with 17 years of experience (K.L.) adjudicated a final decision. No negative control cases were examined.