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What is CR Technology? | How does Computed Radiography work?

What is Computed Radiography?

How does it work?

Computed radiography (CR) is the digital replacement of conventional X-ray film radiography and offers enormous advantages for inspection tasks – the use of consumables is virtually eliminated and the time to produce an image is drastically shortened.

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Imaging plates are reusable

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No darkroom or chemicals needed

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Reduction in exposure and processing time

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Software-based evaluation and reporting

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Simple digital information exchange and archiving

Furthermore, more details are visible and analyzable with computed radiography due to a higher dynamic range when compared to film. Other advantages over film include a more simplified workflow, a safer working environment for operators and a more environmentally-friendly chemical-free process.

CR technology in three steps

  1. Instead of film, an imaging plate is exposed to X-ray or gamma radiation.
  2. The imaging plate is digitized by the scanner and then erased for immediate reuse.
  3. The digital image is then displayed on a computer monitor for evaluation with specialized software.
Imaging plate scanner

How exactly does CR technology work?

In computed radiography, when imaging plates are exposed to X-rays or gamma rays, the energy of the incoming radiation is stored in a special phosphor layer. A specialized machine known as a scanner is then used to read out the latent image from the plate by stimulating it with a very finely focused laser beam. When stimulated, the plate emits blue light with intensity proportional to the amount of radiation received during the exposure. The light is then detected by a highly sensitive analog device known as a photomultiplier (PMT) and converted to a digital signal using an analog-to-digital converter (ADC). The generated digital X-ray image can then be viewed on a computer monitor and evaluated. After an imaging plate is read, it is erased by a high-intensity light source and can immediately be re-used - imaging plates can typically be used up to 1000 times or more depending on the application.

What should be considered when deciding for CR?

Basically, CR technology can be considered as the digital replacement of conventional X-ray film. Imaging plates are used with the same radiographic inspections methods and techniques as film and are also available in different system classes (image quality) which have different required exposure times. However, with CR technology it is not just the imaging plate type that affects image quality - the scan settings used by the scanner are also crucial. In particular, the resolution capability of the scanner (basic spatial resolution or SRb) plays an important part in determining image quality.

With this in mind, DÜRR NDT developed the HD-CR 35 NDT - the world's first scanner that achieves a basic spatial resolution of 30 μm with a laser focus of merely 12.5 μm (when used with high-resolution imaging plates). This performance was confirmed via certification by the Federal Institute for Materials Research and Testing (BAM). With its variable laser focus size, the HD-CR 35 NDT can also be easily adapted for inspection applications with less demanding basic spatial resolution requirements. If only low resolution is required, the CR 35 NDT with a fixed laser focus of 50 μm may also be perfectly suitable.

New possibilities with digital images

  • Digital magnification allows better detail viewing
  • Image optimization with specialized filters for improved defect detection
  • Histogram adjustment for optimal viewing
  • Annotation and drawing tools
  • Special analysis tools: e.g. for automated wall thickness measurement
  • Simple report generation
  • Standardized data exchange via the DICONDE format
  • Global data exchange via a local network and/or the Internet
  • Digital archiving and backup
X-ray inspection software

Film and Computed Radiography comparison

  Film CR
Exposure medium Film Imaging plate (reusable)
Processing Darkroom conditions and chemistry required No darkroom conditions or chemistry required
Processing time 8 minutes 1-3 minutes (depending on scan resolution)
Evaluation Film viewer Computer with viewing/analysis software
Archiving Film archive room (humidity and temperature-controlled) PC, cloud / remote network server
Availability Unique master copy Unlimited copies with possibility to access from any location

Exposure time

C4 film (Structurix D5 / Industrex T200)
100%
CR imaging plate
60%
C5 film (Structurix D7 / Industrex AA400)
100%
CR imaging plate
30%
Cost savings* Company A Company B
Exposures per day 25 150
Savings per exposure EUR 2,39 EUR 2,11
Savings per year
(250 work days)
EUR 14.910,95 EUR 79.154,70

*including film developer/fixer, cleaning, archival costs. 10 x 48 cm film/imaging plate format, 500 cycles per imaging plate. Based on 2017 German market prices (MRRP).

CR Products

HD-CR 35 NDT imaging plate scanner
HD-CR 35 NDT imaging plate scanner

Imaging Plate Scanner

High resolution CR scanner for all NDT radiography applications - weld testing, profile images and aerospace.

Imaging Plates
Imaging Plates

Imaging Plates

IPs are available in different resolutions and all standard formats and, on request, in special sizes and custom shapes.

D-Tect NDT X-ray inspection software
D-Tect NDT X-ray inspection software

D-Tect Software

All functions from image acquisition, analysis and related report generation, to export, archiving and database management are included.

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