Effect of visualization display colour on polyp conspicuity at virtual colonoscopy

Aim: To investigate the effect of different colour three-dimensional (3D) displays on polyp detection at virtual colonoscopy (VC). Methods: Five VC trained observers were shown 'brief flashes' (lasting 0.2 s) of 125 3D endoluminal image snap-shots, repeated for each of six display colours (750 images total). One hundred images contained a single polyp (diameter range 5-42 mm) and 25 contained no polyp ('normal'). Images were reviewed in random order over five reading sessions, readers recording either normality or presence and location of a polyp. Multilevel logistic regression was used to examine any influence of colour on polyp detection stratified according to polyp size (medium 5-9 mm/large ≥10 mm). The kappa statistic was used to assess effect of colour on observer agreement. Results: Individual reader polyp detection rates ranged between 75-94%. Compared to the default pink 'soft tissue' display, the odds of polyp detection were 0.65 (CI 0.41,1.01) for green, 0.82 (0.53,1.30) for blue, 1 (0.63,1.59) for red, 1.12 (0.7,1.79) for monochrome, and 1.15 for yellow (0.72,1.84). Overall, there was no significant difference between the displays (p = 0.11). Including normal cases, there was no overall difference in correct case classification between the six colours (p = 0.44). The odds of detecting large versus medium polyps was significantly greater for 3/5 observers; odds ratio (OR) 2.84-10.1, although unaffected by display colour (p = 0.3). Conclusion: The background colour display generally has a minimal effect on polyp detection at VC, although green should be avoided