Abstract
Background and Study Aims: Digital color information is obtained in “bits” or parcels of information for each
color (red, green, blue) of a picture. As the number of bits increases, the amount
of color information increases, and more colors can be displayed on a suitable monitor.
With eight bits of information, 256 colors can be displayed; with 16 bits, several
thousand colors can be displayed; and with 24 bits, more than 16 million colors can
be displayed. We sought to determine the minimum requirement for diagnostic-quality
endoscopy images in a prospective blinded trial.
Patients and Methods: Twenty-four bit color images were digitally acquired from the processor using a video
card and a personal computer. Ten lesions were chosen to represent the gamut of lesions
seen in the upper gastrointestinal tract. Images were simultaneously obtained with
decreasing color information (16 and eight bits), and these served as controls. Eleven
observers were the test subjects. Six endoscopy nurses, who perform color calibrations,
and five endoscopists viewed the images. Eight-bit, 16-bit and 24-bit color images
were coded and displayed simultaneously on a high-resolution color monitor (Supermac
Technology, Sunnyvale, CA) that can display 16.8 million colors.
Results: All images were considered to be of diagnostic quality by the observers, and the
area of abnormality was identified and the diagnosis made in all cases. Of 110 viewings
of the 24-bit image, on 45 occasions (41 %) the viewers could detect no difference
between it and the eight-bit and 16-bit images. In 23 (21 %), the 24-bit color image
was correctly recognized, and on 21 occasions (19 %) the 24-bit image was incorrectly
identified as eight-bit or 16-bit. Similar data were obtained with viewings of the
eight-bit and 16-bit images.
Conclusions: Our results demonstrate that, with current endoscopic technology, 256 colors may
be as good as 16 million. Eight-bit color is an acceptable image standard for routine
endoscopy.
