title: Perceived features reported as nodules: interpretation of spiral chest CT scans.
abstract: OBJECTIVE
  The purpose of this study was to evaluate nontarget locations identified in a study of lung nodule detection with spiral computed tomographic (CT) scans that compared cine and film presentations.
  
  
  METHODS
  In a previous study of lung nodule detection, eight observers were asked to identify 10 nodule locations in each of five CT scans containing eight simulated nodules. In the current study, each nontarget location that was reported more than once in the previous study was inspected with a stack-mode display in both cine and static modes. The nontarget locations were evaluated for probable identity, shape, and distance from the peripheral lung surface.
  
  
  RESULTS
  Fifty-two nontarget locations included clinically undetected pulmonary nodules (n = 12), lymph nodes (n = 2), unclassifiable structures (n = 2), pleural scars (n = 8), and vascular structures (n = 28). Five nontarget locations contained vessels with complex courses apparent only with cine mode. As a group, nontarget locations were significantly closer to the periphery than would be expected by chance (for all locations, P < .0001; for locations not touching the pleural surface, P = .013).
  
  
  CONCLUSIONS
  The lower reporting threshold caused by the observer instructions to find 10 targets resulted in increased reporting of structure with a nodular appearance. The locations of these reports in the lung periphery can be attributed to the relationship between frequent disease and a nearly featureless background in the lung periphery.
authors.affiliation: Department of Radiology, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02115, USA.
authors.forename: F L
authors.initials: FL
authors.lastname: Jacobson
authors.forename: P F
authors.initials: PF
authors.lastname: Judy
authors.forename: U
authors.initials: U
authors.lastname: Feldman
authors.forename: S E
authors.initials: SE
authors.lastname: Seltzer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D002921:Cicatrix / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging*; D008171:Lung Diseases / Q000000981:diagnostic imaging*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging; D008198:Lymph Nodes / Q000000981:diagnostic imaging; D008875:Middle Aged; D014057:Tomography, X-Ray Computed