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Digital Radiography - X-Ray Radiation Advanced NDT

Digital radiography is an advanced technology based on digital detector systems in which the x-ray image is displayed directly on a computer screen without the need for developing chemicals or intermediate scanning.

The incident x-ray radiation is converted into an equivalent electric charge and then to a digital image through a detector sensor.

Compared to other imaging devices flat panel detector provides high quality digital images with better signal to noise ratio and improved dynamic range, which in turn provides high sensitivity for radiographic application.

Flat panel detectors work on two different approaches, namely indirect conversion and direct conversion. Indirect conversion flat panel detectors utilize a photo diode matrix of amorphous silicon.

Direct conversion flat panel detectors use a photo conductor like amorphous selenium (a-Se) or Cadmium telluride (Cd-Te) on a multi-micro electrode plate and provides the greatest sharpness and resolution. The information on both types of detectors is read by thin film transistors.

In the direct conversion process, when photons impact over the photo conductor, like amorphous Selenium, they are directly converted to electronic signals which are amplified and digitised.  As there is no scintillator, lateral spread of photons is absent here ensuring a sharper image.  This differentiates it from indirect construction.

TWI Resources

  • TWI has two digital x-ray systems: a 450kV broad focus system and a 225kV micro-focus system.


  • Shorter exposure times
  • Real Time Applications
  • Use of analysis tool and defect recognition software
  • Improved detail detectability
  • Enhanced SNR and linearity
  • Reduced inspection time as no chemical processing of film is required
  • Eliminates processing Chemical hence safe for environment
  • Digital image enhancement and data storage
  • Higher productivity
  • Portability
  • Increased dynamic range enables multiple thickness to be inspected in one shot
  • Immediate feed back


  • Aerospace product examination
  • Detection of Corrosion Under Insulation (CUI) in petrochemical, oil and gas and power generation industries
  • Detection of Flow accelerated corrosion
  • Foreign object detection
  • Casting and weld inspection
  • Inspection of composites and fibre reinforced components


An Appreciation of Advanced Radiography (CR, DR and CT) – 4 day training course covering: Computerised Radiography (CR), Digital Radiography (DR) and Computerised Tomography (CT). Suitable for Radiographic Testing Operators qualified to at least Level 1, in accordance with ISO 9712, engaged in radiographic testing/interpretation who need to update their knowledge to incorporate digital radiography, and personnel engaged in the supervision, control and interpretation of radiographic images who wish to expand their knowledge to incorporate digital radiography.

For more information about TWI's non-destructive testing (NDT) services, please email

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