Improved Detectability with Dynamic Gain for Digital Radiography

Industrial imaging applications that exhibit large variations in attenuation can sometimes require multiple radiographs in order to achieve maximum contrast and detectability. Some examples are cylinder heads, engine blocks, large bore diameter pipes, and welded rod or rebar. These components, depending upon the incident radiation path and energy of the x-rays, can have more than 16 bits of dynamic range variation. This can result in areas of the radiograph becoming radiation “starved” or saturated, reducing the useable area in the image for qualified inspections. Dynamic Gain on digital radiography panels extends full range contrast scales, by automatically selecting the appropriate gain on a pixel-by-pixel basis based on the incident radiation exposure. This essentially maintains appropriate contrast and signal-to-noise-ratio in the radiograph, increasing the probability of detection reducing the number of shots that are required by increasing the analytical area. Specific examples will demonstrate penetrometer detectability with and without dynamic gain.

References
  1. Proceedings of SPIE, Vol. 5368, San Diego, CA, “Multiple gain ranging readout method to extend the dynamic range of amorphous silicon flat panel imagers”, February 2004
  2. ASTM Standard 2002, “Standard Practice for Determining Total Image Unsharpness in Radiology”, 2009
  3. ASTM Standard Practice 2597-07E, “Standard Practice for Manufacturing Characterization of Digital Detector Arrays”, April 2008
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