What is Computed Radiography?

How does the Computed Radiography method work?

In Computed Radiography, when imaging plates are exposed to X-ray or gamma rays, the energy from the incoming radiation is stored in a special phosphor layer. A specialized machine, known as a scanner, is then used to read the latent image from the plate by stimulating it with a finely focused laser beam.

When the plate is stimulated, it emits blue light with an intensity proportional to the amount of radiation it received during exposure.

The light is then detected by a very sensitive analog device known as a photomultiplier tube (PMT) and converted into a digital signal by an analog-to-digital converter (ADC). The generated digital X-ray image can then be viewed on a computer screen and evaluated. After an imaging plate has been read, it is erased by a high-intensity light source and can be reused immediately – imaging plates can typically be reused up to 1,000 times or more, depending on the application.

What to consider when choosing Computed Radiography (CR)

Essentially, Computed Radiography can be considered the digital replacement for conventional X-ray film. Imaging plates use the same radiographic inspection methods and techniques as film and are also available in various system classes (image quality) requiring different exposure times. However, with Computed Radiography, it’s not just the type of imaging plate that affects image quality – the scanning settings used by the scanner are also crucial. In particular, the scanner’s resolution capability (basic spatial resolution or SRb) plays an important role in determining image quality.

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

New possibilities with digital images

• Digital zoom provides better detail visibility
• Image enhancement using 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 DICONDE format
• Global data exchange via a local network and/or the Internet
• Digital archiving and backup

EXPOSURE TIME

COST SAVINGS*

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