Katsuhiro Ichikawa PhD, Presenter: License agreement, Totoku Electric Co, Ltd Research support, Totoku Electric Co, Ltd

Masayuki Nakazawa, Abstract Co-Author: Employee, Konica Minolta Group Employee, Graphic, Inc

Hitoshi Yoshimura, Abstract Co-Author: Employee, Konica Minolta Group

Color liquid crystal displays (LCDs) are becoming more popular than monochrome LCDs because of their availability to display color information. However, many radiologists point out that color LCDs are somewhat inferior to monochrome LCDs to interpret monochrome images, and there are some reports that describe inferior noise properties of color LCDs. In order to reduce this inferiority, we derived three types of slightly blue-tone look-up tables (Blue-LUTs) that realize monochrome image displaying like blue-base films. The purpose of this study is to investigate the usefulness of these Blue-LUTs by means of physical evaluations and a perceptual low-contrast detection study.

The Blue-LUTs were developed to improve the noise properties and simultaneously achieve up to 1786-step gray-scale. We developed an image viewing software corresponding to the Blue-LUTs and required test patterns were displayed on a 2 mega-pixel medical grade color LCD by using the software. Physical performances of resolution (modulation transfer function: MTF) and noise (noise power spectrum: NPS) were evaluated as compared with normal (clear) mode. In addition, we performed a detection study by five radiological technologists, using low-contrast objects displayed at a random position.

The MTFs of all Blue-LUTs and the normal mode are almost equivalent. The NPS were improved as the blue-tone was increased by the color configurations in the LUTs. The low-contrast detectability was improved corresponding to the NPS improvement. One of the Blur-LUTs was given much higher detectability (70.3%) than that of the normal mode (10.0%). A single pixel on a color LCD is made of three colored elements called RGB sub-pixels, which generate unneeded periodic pattern noise. Its effect appeared as the increased noise level in the NPS results. The Blue-LUTs worked to reduce the luminance variation among the R,G and B sub-pixels. Therefore the NPSs were improved and consequently the detectability was improved.  

The Blue-LUTs for color LCDs have potential to improve the image quality for monochrome image displaying. The potential was demonstrated by the results from the NPS measurement and the detection study.

Since the Blue-LUTs for color LCDs can reduce the periodic pattern noise from the RGB sub-pixels, the LUTs will be effective to improve the inferiority of color LCDs for monochrome image displaying.

Ichikawa, K, Nakazawa, M, Yoshimura, H, Usefulness of Slightly Blue-tone Look-up Tables for Color Liquid Crystal Displays on Displaying Monochrome Images.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8010511.html