Introduction to Grayscale Calibration and Related Aspects of Medical Imaging Grade Liquid Crystal Displays Kenneth A. Fetterly, 1 Hartwig R. Blume, 2 Michael J. Flynn, 3 and Ehsan Samei 4,5,6 Consistent presentation of digital radiographic images at all locations within a medical center can help ensure a high level of patient care. Currently, liquid crystal displays (LCDs) are the electronic display technology of choice for viewing medical images. As the inherent luminance (and thereby perceived contrast) properties of different LCDs can vary substantially, calibration of the luminance response of these displays is required to ensure that observer perception of an image is consis- tent on all displays. The digital imaging and communi- cation in medicine (DICOM) grayscale standard display function (GSDF) defines the luminance response of a display such that an observer's perception of image contrast is consistent throughout the pixel value range of a displayed image. The main purpose of this work is to review the theoretical and practical aspects of calibration of LCDs to the GSDF. Included herein is a review of LCD technology, principles of calibration, and other practical aspects related to calibration and observ- er perception of images presented on LCDs. Both grayscale and color displays are considered, and the influence of ambient light on calibration and perception is discussed. KEY WORDS: Medical imaging grade liquid crystal displays (LCDs), DICOM GSDF, observer perception, ambient light INTRODUCTION C onsistent presentation of medical images is important to ensure a high level of patient care. Medical centers that were (or are) film-based ensured consistent image quality by distributing a single hard copy rendition of a radiographic examination to the various care providers. Given that the providers viewed the image on a light box of comparable luminance, all who viewed the image were provided the same rendition of that image. Medical practices and radiology depart- ments are evolving to a digital rather than film- based image acquisition and distribution system. In many instances, this allows multiple providers in different locations to have simultaneous access to the images and provides the potential for better and more efficient patient care. Similar to a film- based practice, delivering a high-quality radio- graphic examination to all care providers helps ensure a consistent and high level of patient care. Given that many newly acquired images are digital, there is a potential to view them on any number of computer systems. Computers as com- mon as a standard personal computer (PC) or as sophisticated as a picture archival and communi- cations system (PACS) work station may be used to view images. The need for consistent image presentation on this wide selection of work stations has been recognized 1,2 as part of a broader description of a high-quality display, which is required for medical image presentation. 3,4 For 1 From the Department of Diagnostic Radiology, Mayo Clinic, Rochester, Minnesota, USA. 2 From the Seymour, Connecticut, USA. 3 From the Department of Radiology, Henry Ford Health Systems, Detroit, Michigan, USA. 4 From the Department of Radiology, Duke University Medical Center, Durham, North Carolina, USA. 5 From the Department of Physics, Duke University Medical Center, Durham, North Carolina, USA. 6 From the Department of Biomedical Engineering, Duke University Medical Center, Durham, North Carolina, USA. Correspondence to: Kenneth A. Fetterly, PhD, Department of Diagnostic Radiology, Mayo Clinic, Rochester, Minnesota, USA, tel: +1-507-2553547; fax: +1-507-266-0884; e-mail: fetterly. kenneth@mayo.edu Copyright * 2007 by Society for Imaging Informatics in Medicine Online publication 1 March 2007 doi: 10.1007/s10278-007-9022-y Journal of Digital Imaging, Vol 21, No 2 (June), 2008: pp 193Y207 193