Amarpreet S. Chawla

Real-time MTF evaluation of displays in the clinical arena

Abstract not available.

The liquid crystal display (LCD) for medical imaging in comparison with the cathode ray tube display (CRT)

This paper discusses display parameters such as display function, contrast, dynamic range, veiling glare and spatial resolution of displays useful in digital radiology. After a review of the traditional display in diagnostic radiology, namely the film-lightbox, based on the film-screen combination, the paper concentrates on the Active Matrix Liquid Crystal Flat Panel Display (AM-LCD). The AM-LCD will most likely mature and may become the display of choice in the near future, replacing the Cathode Ray Tube Display (CRT), which is presently the dominating softcopy display. A comparison between pertinent performance characteristics of AM-LCD and CRT demonstrates that spatial resolution (Modulation Transfer Function or MTF) and veiling glare for the AM-LCD are already superior to those of the CRT.

Performance evaluation of LCD displays

This paper presents measurements of display function, spatial resolution (MTF), grayscale precision and spatial noise of three monochrome LCDs. Each of these LCDs features a different method to increase the grayscale precision: Frame Rate Modulation, Sub-Pixel Modulation and Aperture Modulation. A CCD camera was used for the evaluation. It imaged a small portion of the LCD, usually with over-sampling of between 115:1 and 8:1 CCD pixels per LCD pixel. The evaluated systems have image quality that in many respects is superior to CRT displays. Most impressive is the spatial resolution. The MTF of the systems investigated is almost unity. The typically 8 bits grayscale precision can be significantly increased by temporal as well as spatial modulation techniques. It appears that the aperture modulation technique alone can achieve a precision of 10.8 bits or 1800 distinct luminance levels. Spatial noise was evaluated in terms of single pixel signal-to-noise ratio and in terms of the spatial noise power spectrum. Single pixel signal-to-noise ratios for one LCDs were in the order of 100:1, and for another one the spatial noise power density of the normalized NPS at spatial frequencies below the LCD Nyquist frequency of 2.4 lp/mm was about 3.1E-5 mm2, values which are in the order of those from high performance CRTs.

Why should you calibrate your display

This paper discusses the issue of calibration for the growing number of electronic displays used in the filmless and electronic radiology departments. It concentrates on CRT and LCD displays as these are the most matured electronic display systems available at this time. It is shown that grayscale calibration is necessary and useful to optimally display the information contained in the various digital images in diagnostic radiology. In addition properties and drawbacks of four prevalent standards for display function have been discussed.

Display of mammograms on a CRT

In most radiological imaging workstations the monochrome cathode ray tube (CRT) is the electronic display of choice. The CRT offers the best performance; it is the most highly developed, mature and reliable display in common use. Unfortunately, because of limited spatial resolution and because of limited dynamic range, the efficacy of soft-copy versus hard-copy diagnosis has been challenged.