Sharpness is an important factor in digital radiography, contributing towards the detection of discontinuities. However, the overall image quality is dependent upon the brightness, sharpness, and overall noise level in the image. Radiography can be used to detect internal discontinuities such as holes, inclusions, shrinkage, and cracks. Typically, discontinuities are missing material in a part with a specific material type and thickness. When an image is displayed for interpretation, what ultimately matters is whether the relevant features are sufficiently visualized. Image quality metrics provide a description of the detection capability. Medical radiology and industrial radiography use different terms to describe image quality, however both terminologies illustrate the same phenomenon. A discussion of detective quantum efficiency (DQE), modulation transfer function (MTF), noise power spectrum (NPS), basic spatial resolution (SRb), signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and equivalent penetrameter sensitivity (EPS) will be presented as part of this paper.
1. Quinn, R., Sigl, C., Garrett, W., Splettstosser, D., Titus, E., Radiography in Modern Industry, fourth edition, Eastman Kodak Company, Rochester, NY, 1980.
2. ASTM E0094, “Standard Guide for Radiographic Examination Using Industrial Radiographic Film,” ASTM International.
3. ASTM E2698, “Standard Practice for Radiological Examination Using Digital Detector Arrays,” ASTM International.
4. Rose, A., "A Unified Approach to the Performance of Photographic Film, Television Pick-Up Tubes, and the Human Eye," Journal of the Optical Society of America, Volume 38, pages 196-208, 1948.
5. Shaw, R., "The Equivalent Quantum Efficiency of the Photographic Process," Journal of Photographic Science, Volume 11, pages 199-204, 1963.
6. Dainty, J. C. and Shaw, R., Image Science: Principles, Analysis and Evaluation of Photographic Type Imaging Processes, Academic Press, New York, NY, 1974.
7. ASTM E2002, “Standard Practice for Determining Total Image Unsharpness and Basic Spatial Resolution in Radiography,” ASTM International.
8. ASTM E2445, “Standard Practice for Performance Evaluation and Long Term Stability of Computed Radiography Systems,” ASTM International.
9. ASTM E2446, “Standard Practice for Manufacturing Characterization of Computed Radiography Systems,” ASTM International.
10. Ewert, U., Zscherpel, U., Bavendiek, K., "Image Quality in Digital Industrial Radiography," Materials Evaluation, Volume 70, No. 8, pages 955-964, 2012.
11. LaCivita, K., Ewert, U., "Equivalent Penetrameter Sensitivity as Applied to Computed Radiography," Materials Evaluation, Volume 70, No. 8, pages 925-930, 2012.
12. Ewert, U., Bavendiek, K., Robbins, J., Zscherpel, U., Bueno, C., Gordon, T., Mishra, D., "New Compensation Principles for Enhanced Image Quality in Industrial Radiology with Digital Detector Arrays," Materials Evaluation, Volume 68, No. 2, pages 163-168, 2010.
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