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Demystifying myths in the path of digital transformation of imaging processes

It is essential to understand that exposure conditions largely determine the imaging results that are obtained for a given system.
By Isbel Lázaro. on April 3, 2024
Demystifying myths in the path of digital transformation of imaging processes

By Brian S. White. Textual note taken from Carestream NDT dated April 3, 2024

Introduction – Radiography as science and craftmanship

Obtaining adequate radiographic image quality is the result of the science principles that sustain the radiographic imaging process and also of the craftmanship and experience that the radiographer puts into function while defining radiographic technique (See Figure 1-a).

Demystifying myths in the path of digital transformation of imaging processes
Figure 1.- Factors that affect radiographic image quality.
Demystifying myths in the path of digital transformation of imaging processes
Figure 1-b.- Factors that affect radiographic image quality.

In the case of digital radiography (See Figure 1-b), besides the traditional factors associated with radiographic technique such as source-to-object distance or geometric unsharpness, new parameters such as averaged frames, integration time, pixel intensity or contrast-to-noise ratio (CNR) shall be considered.

Debunking the myth of one-size-fits-all Pixel Intensity

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As DDA systems are becoming more prevalent in industrial radiography, some myths have materialized. One prevalent myth while selecting DDA systems is that pixel intensity determines the CNR and detectability.

It is essential to understand that exposure conditions largely determine the imaging results that are obtained for a given system. New guidelines will require the establishment of a pixel intensity range to achieve acceptable contrast sensitivity. The sensitivity will depend upon the radiographic technique, material type, material thickness, DDA type, integration time and the number of averaged frames. When the same pixel intensity has been obtained, it does not guarantee that the same contrast sensitivity has been achieved. To show this, we conducted an illustrative procedure using a Carestream NDT HPX-DR 3543 DDA, 139 mm image resolution, 139 mm pixel pitch, 14 x 17” active area DDA with both X-rays (see Figure 2) and gamma rays.

Demystifying myths in the path of digital transformation of imaging processes
Figure 2: – Comparison of Averaged Frames for the HPX-DR 3543 DDA It presents a visual comparison of averaged frames for X-ray. The image on the left was at 1 frame, 8 seconds integration time, pixel intensity of 11229, 5 wire visible, contrast-to-noise ratio CNR of 8.35. The image on the right was at 100 frames, 8 seconds integration time, pixel intensity of 11296, 1 wire visible, contrast-to-noise ratio CNR of 40.75. from Brian S. White Presentation at ASNT 2020: The Annual Conference November 9-12 “Exposure Guidance and the Myth of Pixel Value Dependence for Digital Detector Array Radiography.”

Conclusion

In this example, even though the pixel intensities were virtually the same, the image quality for the image on the right is significantly better. This set of images speaks for itself, debunking this myth.

For readers interested in exploring how digital radiography (DR) can be integrated to processes: https://www.carestream.com

Here are some supplementary information resources from Carestream NDT’s products and services portfolio:

Products:
HPX-DR 3543 PE Non-Glass, Large Format Detector,
HPX-DR 4336 GH High-Resolution, Large Format Detector,
HPX-DR 2530 PH High-Resolution, Compact Detector,
HPX-DR 2530 GC High-Speed, Compact Detector,
INDUSTREX Digital Viewing Software,
Training: 
Advanced Industrial Radiographic Training Academy

An expanded version of this article may be found at : https://www.carestream.com/

References:

  1. ASNT, Nondestructive Testing Handbook, Vol. 3: Radiographic Testing, fourth edition, Chapters 9 and 11, Columbus, OH, American Society of Nondestructive Testing.
  2. White, B., Article “Exposure Guidance and the Myth of Pixel Value Dependence for Digital Detector Array Radiography”ASNT Annual Conference, Virtual, 2020.

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Source: www.carestream.com