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·Methods and Instrumentation
Computed Radiography: The Future of Radiographic Inspection
Frederick A. MorroComputed Radiography Specialist
FUJI NDT SYSTEMS FUJIFILM I&I - Imaging & Information
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·Table of Contents ·Methods and Instrumentation | Computed Radiography: The Future of Radiographic InspectionFrederick A. MorroComputed Radiography Specialist FUJI NDT SYSTEMS FUJIFILM I&I - Imaging & Information Contact |
Organizations which use Radiographic Inspection as a tool, as well as manufacturers of the various components of RT systems have strived to develop more efficient methods of accomplishing the inspection cycle, such as automated film processing and improved x-ray generation systems.
One particular goal of many of the parties involved was the elimination or the reduction of x-ray film consumption. Over the years, many companies have developed filmless "Real Time" or "Radioscopic" technologies using a variety of imaging modules, advanced focal spot technology, and subsequent digital image processing, archiving and storage media.
Many Imaging companies developed systems to perform these tasks, and many are still in use today. "Real Time" or "Radioscopic Systems" design and manufacture became a cottage industry for RT applications.
Although filmless technology was successful in many applications, there were always limitations to be considered:
Image Spatial Resolution issues could be addressed by the implementation of "Mini" and "Micro" focus x ray tube technology, which did compromise field of view characteristics, resulting in even further sophistication of product handling system(s).
Computed radiography- "CR" is one of the latest developments in the new genre of filmless RT. Having been commercially available since the early 1980's, recent improvements in storage phosphor, laser, and computer technology have made "CR" a very viable alternative to film based RT systems, with many of the classic considerations having been addressed.
"CR" features:
Computed Radiography employs Imaging Phosphor Storage Technology, which when irradiated, stores a latent radiographic Image for am unspecified period of time, in the same fashion as classical x-ray film
The Imaging Plate is flexible, untethered, and has no power supply. Imaging Plates are mass-produced, under the same rigid Quality Control Standards as RT Film.
Latent Images are extracted from a "Stored" status by laser excitation, causing Photostimulable Luminescence (PSL), which is scanned, file formatted, exported, and viewed. Imaging Plates are subsequently erased, ready for re-use. The complete "Read and Erase" cycle is less than one minute for a 14" x 17" Imaging plate (Full 4K image format), 35 seconds for an 8" x 10" Imaging plate.
Pixel density for a 14" x 17" imaging plate is 3560 x 4320 (4K) pixels per scene, as compared to 1 K or 1.5 K images commonly displayed with other Digital Imaging devices.
Original Fuji "CR" image files are encrypted and tamper proof. These files can be exported and re-filed as "TIF", BITMAP", "SCSI", etc. The original Image, however, remains in a proprietary format.
The cassette loaded with the Imaging Plate is simply substituted for the film cassette, and irradiated in the same fashion as a standard RT technique. All existing exposure hardware and containment cells can be used. It should be noted that typical exposures are reduced by approximately 60%, with no degradation of the signal to noise ratio of the resultant image.
After exposure, the cassette is inserted into the "CR" reader. At this point "Read" enhancement algorithms can be selected and applied automatically during the "Read" process. These "pre-selections" include:
EDR is a proprietary feature, which can adjust Gray Scale values automatically, with no post read adjustments, despite variations in the actual radiation dose applied during the RT technique. It is, in essence, an Automated Density Control Feature.
All the Pre-Set Enhancements are applied to the image file along with any desired demographic data. Demographic data can be introduced by magnetic card or manually entered.
The Image file is transferred to the workstation
The Imaging Plate is erased
The Imaging Plate is automatically re-inserted into the cassette. Ready for re-use.
Cycle time is less than one minute for a 14"x 17" Imaging Plate, 35 seconds for an 8" x 10" Imaging Plate.
Imaging Plates can be continuously processed, with all Image files being stored and inventoried at the system workstation.
Multiple image files can be selected and displayed in a thumbnail format, or in a sequential full screen display.
Images selected for interpretation are viewed with the pre-dispositioned enhancement algorithms applied at the "Read" process. Post "Read" enhancement can also be performed to assist interpretation. These processes include
Tools can also be utilized, such as:
Re-Enhanced Images can be saved as sub-directories of the original image, complete with annotations, commentary, and various pointers. These are saved in the form of overlays, having no detrimental effect on original image data.
It should also be noted that Re-Enhancement activities could be used to develop new "Read" menus at the input terminal of the reader. The workstation can serve as an input or output device.
In all cases, image quality was:
The following Images being displayed are typical of "CR" performance:
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