Influence of visual distractors on detectability of liver nodules on contrast-enhanced spiral computed tomography scans.
OBJECTIVE
The authors evaluated the ability of observers to identify simulated nodules placed electronically on normal contrast material-enhanced computed tomography (CT) scans of the liver to assess the effect of nodule size and polarity on detection and localization.


METHODS
Seven readers evaluated two sets of CT scans that contained 80 stimuli each. The simulated nodules were either darker or brighter than the contrast-enhanced liver and were 5.6-8.0 mm in diameter. Readers were asked to find the most suspicious-looking nodule on each section and rate the likelihood that the chosen location actually contained a nodule.


RESULTS
The fraction of nodules found by each observer was substantially greater for dark nodules than for bright ones (0.679 +/- 0.03 vs 0.345 +/- 0.045, respectively [mean +/- standard error]). This difference was consistent for all nodule sizes. Additional analyses (including receiver operating characteristic curves of conditional responses) suggested that the presence of bright blood vessels distracted the readers and decreased their ability to find bright nodules.


CONCLUSIONS
Normal vascular structures on contrast-enhanced CT scans of the liver impair an observer's ability to detect bright liver nodules.
Wester
C
C
Department of Radiology, Harvard Medical School, Brigham and Women's Hospital, Boston, MA 02115, USA.
Judy
P F
PF
Polger
M
M
Swensson
R G
RG
Feldman
U
U
Seltzer
S E
SE
D006801:Humans; D008099:Liver / Q000098:blood supply; D008113:Liver Neoplasms / Q000000981:diagnostic imaging*; D015588:Observer Variation; D019047:Phantoms, Imaging; D012372:ROC Curve; D011856:Radiographic Image Enhancement; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014796:Visual Perception