Comparison of Color LCD and Medical-grade Monochrome LCD Displays in Diagnostic Radiology

In diagnostic radiology, medical-grade monochrome displays are usually recommended because of their higher luminance. Standard color displays can be used as a less expensive alternative, but have a lower luminance. The aim of the present study was to compare image quality for these two types of displays. Images of a CDRAD contrast-detail phantom were read by four radiologists using a 2-megapixel (MP) color display (143?cd/m²?maximum luminance) as well as 2-MP (295?cd/m²) and 3-MP monochrome displays. Thirty lumbar spine radiographs were also read by four radiologists using the color and the 2-MP monochrome display in a visual grading analysis (VGA). Very small differences were found between the displays when reading the CDRAD images. The VGA scores were ?0.28 for the color and ?0.25 for the monochrome display (p?=?0.24; NS). It thus seems possible to use color displays in diagnostic radiology provided that grayscale adjustment is used.

INTRODUCTION

Digital radiology has many advantages compared to film-based radiology. One is that the functions that used to be performed by the film now can be divided into four separate steps: data acquisition, image processing, data storage, and image display. Each of these steps can and should be optimized separately. In the last of these four steps, the information in the digital image is transferred to the observer, usually as variations in light and color from a display. It is important to have displays of high quality in order not to degrade the last step in the image-forming process. In the literature, medical-grade monochrome displays are usually recommended, mostly because of their higher luminance.¹?The major drawback of the monochrome displays is their very high cost, which has prompted some institutions to use standard color displays, which are considerably less expensive because they are mass-produced for the general computer market.

In recent years, there has been a trend toward switching from displays based on cathode-ray tubes (CRT) to flat panels based on liquid crystal displays (LCD). This is supported by several studies.^2,3

We wished to test the null hypothesis that there is no significant difference in a calculated image quality factor between contrast-detail phantom images displayed on a consumer-grade color LCD display and a medical-grade monochrome LCD display having the same resolution. We also wished to test the null hypothesis that there is no significant difference in diagnostic image quality between clinical radiographs of the lumbar spine displayed on the same monitors.

The comparisons between color and monochrome displays with different images of the contrast-detail phantom and levels of ambient illuminance are shown in Figure?2. Using a flat-panel image at low illumination, the mean image quality figure (IQF) was 40 for the 2-MP color and 42 for the 2-MP monochrome display. At high illumination, the corresponding IQF values were 44 and 42. When changing to the storage phosphor plate image, the IQF values were increased to 51 and 52, indicating inferior image quality, still with a very small difference between the two displays. When exchanging the monochrome display for a 3-MP unit with no zoom allowed, the IQF values were 44 for the 2-MP color and 40 for the 3-MP monochrome display.

CONCLUSIONS

In summary, we did not find any significant difference in image quality between a medical-grade monochrome LCD display and a color LCD display of equal spatial resolution, neither with a contrast-detail phantom nor in a visual grading analysis when adjustment of the grayscale was used to its full potential.