Resolution and noise measurements of five CRT and LCD medical displays.

The performance of soft-copy displays plays a significant role in the overall image quality of a digital radiographic system. In this work, we discuss methods to characterize the resolution and noise of both cathode ray tube (CRT) and liquid crystal display (LCD) devices. We measured the image quality of five different commercial display devices, representing both CRT and LCD technologies, using a high-quality charge-coupled device (CCD) camera. The modulation transfer function (MTF) was calculated using the line technique, correcting for the MTF of the CCD camera and the display pixel size. The normalized noise power spectrum (NPS) was computed from two-dimensional Fourier analysis of uniform images. To separate the effects of pixel structure from interpixel luminance variations, we created structure-free images by eliminating the pixel structures of the display device. The NPS was then computed from these structure-free images to isolate interpixel luminance variations. We found that the MTF of LCDs remained close to the theoretical limit dictated by their inherent pixel size (0.85 +/- 0.08 at Nyquist frequency), in contrast to the MTF for the two CRT displays, which dropped to 0.15 +/- 0.08 at the Nyquist frequency. However, the NPS of LCDs showed significant peaks due to the subpixel structure, while the NPS of CRT displays exhibited a nearly flat power spectrum. After removing the pixel structure, the structured noise peaks for LCDs were eliminated and the overall noise magnitude was significantly reduced. The average total noise-to-signal ratio for CRT displays was 6.55% +/- 0.59%, of which 6.03% +/- 0.24% was due to interpixel luminance variations, while LCD displays had total noise to signal ratios of 46.1% +/- 5.1% of which 1.50% +/- 0.41% were due to interpixel luminance variations. Depending on the extent of the blurring and prewhitening processes of the human visual system, the magnitude of the display noise (including pixel structure) potentially perceived by the observer was reduced to 0.43% +/- 0.01% (accounting for blurring only) and 0.40 +/- 0.01% (accounting for blurring and prewhitening) for CRTs, and 1.02% +/- 0.22% (accounting for blurring only) and 0.36% +/- 0.08% (accounting for blurring and prewhitening) for LCDs.

[1]  Hartwig R. Blume,et al.  Display of medical images on CRT soft-copy displays: a tutorial , 1995, Medical Imaging.

[2]  M L Giger,et al.  Investigation of basic imaging properties in digital radiography. 6. MTFs of II-TV digital imaging systems. , 1985, Medical physics.

[3]  Ehsan Samei,et al.  Assessment of display performance for medical imaging systems: executive summary of AAPM TG18 report. , 2005, Medical physics.

[4]  Jay Bartroff,et al.  Automated computer evaluation and optimization of image compression of x-ray coronary angiograms for signal known exactly detection tasks. , 2003, Optics express.

[5]  Jiahua Fan,et al.  In-field evaluation of the modulation transfer function of electronic display devices , 2004, Medical Imaging: Image-Guided Procedures.

[6]  Ehsan Samei,et al.  AAPM/RSNA physics tutorial for residents: technological and psychophysical considerations for digital mammographic displays. , 2005, Radiographics : a review publication of the Radiological Society of North America, Inc.

[7]  Ehsan Samei,et al.  Physical characterization of a prototype selenium-based full field digital mammography detector. , 2005, Medical physics.

[8]  Ehsan Samei,et al.  Method for in-field evaluation of the modulation transfer function of electronic display devices , 2001, SPIE Medical Imaging.

[9]  Elizabeth A. Krupinski,et al.  Spatial noise of high-resolution liquid-crystal displays for medical imaging: quantitative analysis, estimation, and compensation , 2004, Medical Imaging: Image-Guided Procedures.

[10]  Ehsan Samei,et al.  A method for modifying the image quality parameters of digital radiographic images. , 2003, Medical physics.

[11]  E Samei,et al.  Detection of subtle lung nodules: relative influence of quantum and anatomic noise on chest radiographs. , 1999, Radiology.

[12]  W W Peppler,et al.  Use of a slit camera for MTF measurements. , 1999, Medical physics.

[13]  Aldo Badano,et al.  Noise in flat-panel displays with subpixel structure. , 2004, Medical physics.

[14]  Aldo Badano,et al.  Luminance effects on display resolution and noise , 2002, SPIE Medical Imaging.

[15]  M. Williams,et al.  Noise power spectra of images from digital mammography detectors. , 1999, Medical physics.

[16]  Jiahua Fan,et al.  Characterization of high-resolution liquid crystal displays for medical images , 2002, SPIE Medical Imaging.

[17]  A Workman,et al.  Physical performance measures of radiographic imaging systems. , 1997, Dento maxillo facial radiology.

[18]  Jiahua Fan,et al.  The liquid crystal display (LCD) for medical imaging in comparison with the cathode ray tube display (CRT) , 2002, SPIE Optics + Photonics.

[19]  Thomas Mertelmeier,et al.  Impact of phosphor luminance noise on the specification of high-resolution CRT displays for medical imaging , 1997, Medical Imaging.

[20]  Kenneth D. Compton.  Factors affecting CRT display performance: specifying what works , 2000, Medical Imaging.

[21]  E Samei,et al.  Luminance and Contrast Performance of Liquid Crystal Displays for Mammographic Applications , 2004, Technology in cancer research & treatment.

[22]  E. Samei,et al.  Impact of resolution and noise characteristics of digital radiographic detectors on the detectability of lung nodules. , 2004 .

[23]  E. Samei,et al.  Experimental comparison of noise and resolution for 2k and 4k storage phosphor radiography systems. , 1999, Medical physics.

[24]  Elizabeth A. Krupinski,et al.  Improving visualization of digital mammograms on the CRT display system , 2003, SPIE Medical Imaging.