African Fusion

SAIW Michael Beaugrand from Larivière VIDAR NDTPRO"20 years ago, we saw the transition in photography from 35 mm film to digital cameras. We have since seen a similar transition in the medical market," says Beaugrand, adding that the medical radiography transition is already 100% complete in Scandinavian countries and over 80% in most of the developed world. The NDT fraternity is now going though that same transition, albeit 15 years later, so Beaugrand expects the full transition to digital NDT to be nearing completion 10 to 15 years from now.

Highlighting the advantages of digital radiography, he says that, in principle, the sources, shielding and collection techniques are the same as those use for film based methods. But a detector is used to capture the image instead of film – and there are two detector technologies currently in use, computed radiography (CR) and direct radiography (DR) detectors.

"The post exposure image formation, however, is different from film. Instead of a light box, a computer and monitor are required to view digital radiographs, and instead of the grey exposure shades fixed on photographic film, exposure values are digitally stored as an array of pixels. Each pixel has a value proportional to its radiation exposure, which are converted into analogue grey values of varying brightness on the display monitor," he explains.

Key advantages of digital systems are: the brightness and contrast can be very easily adjusted to suit different areas of the image; magnification is easy; the image can be enhanced and processed; measurements can be applied and used in calculations and statistics; and annotations and stamps (metadata) can easily be incorporated directly into the image file. "I have seen an experienced Level 3 NDT Inspector being amazed by how much more information can be revealed on a digital image simply by zooming into an area of interest and adjusting the contrast," Beaugrand reveals.

"The biggest problem with using digital systems, whether they are CR- or DR-based, is that companies all over the world have millions of film-based radiographs, in vaults and filing cabinets, and these also need to be easy to access and use in one common system," he explains. To monitor changes over time, it is often necessary to compare a radiograph from the past with a current image, and it is very difficult to compare a film on a light box with an image on a computer screen, because the visual quality of the two technologies is far too inconsistent, he points out.

"What was needed, therefore, was a platform that would enable archived radiographs to be digitised so that they could be accessed and used on the same platform and to the same standards as newly collected digital images," he adds.

In transforming the medical radiography market, after an initial period with multiple file formats, the industry decided on a standard file format to streamline procedures and workflow, where all manufacturers adopted the same format. The idea was to enable any image to be transferred between doctors using equipment from different manufacturers without any compatibility problems. This led to the development of the DICOM (digital imaging and communications in medicine) compatibility protocol for the medical imaging profession. "But for the first five years, the focus was on the choice between CR or DR technology and the bridge to film was seen as less important. Today all of the major medical digital imaging providers also provide scanners to convert existing X-rays into the equivalent DICOM digital format,"

DICOM was the forefather of the file format chosen for industrial NDT systems, DICONDE (Digital Imaging and Communications for Non-Destructive Evaluation) a standard established by the ASTM (American Society for Testing and Materials).

Describing how DICONDE is used, Beaugrand says that Larivière is currently digitising all of the historic film for one of its large pipeline construction clients. Using a service vehicle fitted with its VIDAR NDTPRO industrial film digitiser, inspection personnel go into the field and systematically digitise the film archives. "This solution fixes all compatibility problems between the technologies and enables compatible workflows to be employed for film-, CR- or DR-based images," he assures. "It enables images produced from film and digital devices to be treated identically and compared side by side, which is an integral step in enabling digital technology to be fully adopted," he says, before adding, "Can you imagine how many rows of boxes and filing cabinets can be emptied by digitising all the films being stored?"

As well as digitising the film image, the DICONDE standard is also able to capture the metadata associated with an image. Reports, measurements and all of the advantages of digital systems can also, therefore, be applied. "DICONDE and associated film digitisation solutions ensure compatibility between the existing NDT world and all future digital systems. In compatibility tests between seven leading equipment manufacturers, images were found to be100% compatible with the all brands of digital imaging systems and software," he assures.

Describing the specific advantages of the VIDAR NDT PRO, he says that this system offers the NDT industry "a product that not only carries a smaller price tag, but is lighter and has a smaller footprint." The digitiser can handle films as narrow as 2.36ʺ wide and up to 51ʺ long. It also features VIDAR's high-definition CCD (HD-CCD™) solid-state technology, as well as its ADC (automatic digitiser calibration) mechanism, which virtually eliminates variation in image quality an

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