Standards and normalization of displays

Objectives

Explanation of the Dicom grayscale display standard, which should guarantee a reproducible and subjectively similar impression of displayed images at all viewing sites. Aspects of ambient light and calibration and current efforts for further standardization of general image processing operations like subtraction and windowing will be shortly mentioned. The standard covers display on film as well as on monitors, which generally have different luminance ranges. Results will be presented from a limited comparison of the Dicom standard with a proprietary standard on subjective similarity between film and monitor images.

Materials and methods

Medical images from different modalities (X-ray, CT, MR) were presented on film and on a monitor screen according to both grayscale standards. Image specialists were asked to grade the similarity between both representations.

Results

There was no statistically significant difference between the subjective similarity obtained with both standards.

Conclusion

The Dicom standards provide a framework for easy and reproducible exchange of images. Our limited study suggests that the grayscale standard gives acceptable similarity of images on monitor and film. However more extended clinical comparisons are recommended, e.g. on finetuning and calibration.