Vol. 13, No. 1

TNT · October 2015 · 1

The American Society forNondestructive Testing

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Converting to ComputedRadiographyAll too often, people come to me and say, “My company has allotted XX amount of money to get us into computedradiography. What is the best brand?” Thefirst time I was approached with thisquestion, I went into a long explanation ofthe many facets involved with convertingto digital. I eventually answered thequestion, but only after explaining howcomplicated the transition is.

When I was asked that same questionrecently, I just said, “Hire a consultant” tothe inquisitive individual. This may bebecause I had given that speech manytimes before and felt that it mostly fellonto deaf ears. It may be because I did nothave time to go into all of the small details.Either way, it comes back to one simpleconcept: replacing film, the right way, withnew technology, is extremely complicated.

Why is it so Complicated? Anyone who knows me will tell you that Iregard computed radiography simply as afilm replacement (Figure 1). Yet, if it is

simply a film replacement, then why is itso complicated?

When you replace film, you have toreplace your standards. The averagetechnician could shift gears fromtraditional film to computed radiographyin a matter of minutes with some minorhands-on training. However, when itcomes to any type of examination ortechnique within that examination thereare always standards to follow.

Replacing Film in a Modern Industryby Wesley Soape

Figure 1. Film requires processing timeand chemicals, but provides good, clearimages.

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From NDT Technician, Vol. 14, No. 4, pp: 1–4.Copyright © 2015 The American Society for Nondestructive Testing, Inc.

The most prevalent standards are DigitalImaging and Communications in Medicine(DICOM) and Digital Imaging andCommunication in NondestructiveEvaluation (DICONDE). These give thebasic standards for equipment and softwareto follow. The most basic rule is that theimage must remain in a raw state fromformation to archival. Some machine andsoftware combinations filter the imagebefore delivering for review, which is notcompliant of these standards. That is anevaluation that needs to be made firstthing. Your client may accept pre-filteredimages, though that segment is gettingsmaller and smaller. For most work,DICOM/DICONDE compliance isnecessary.

If your client requires DICOM/DICONDEcompliance, you will need to refer tosomething like ASTM E 2339 or ASTM E 2738 as accepted standards forcompliance (ASTM, 2011; ASTM, 2013).ASTM E 2445 will give you the guidelinesfor performance evaluation and long-term stability, which is an important part of using any method or technique(ASTM, 2014). As a standard guide tocomputed radiography, you will needASTM E 2007 (ASTM, 2010). Those arejust a few ASTM International standards. Ifyou use another evaluation standard, youwill need to check into your applicablerequirements.

There are also considerations withcertification standards. You need to see how digital technology fits into yourcertification program along with a possiblerevamp of your own written practice. Thatcould become a considerable task andexpense, depending on the size of thecompany.

With the introduction and evolution ofdigital technology in our modern world ofradiography, we have lots of standards withwhich to comply. Most of these standardsgo completely unnoticed by new andseasoned technicians alike, but clients arebeginning to embrace these new standards,often before the service provider does.

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Figure 2. Digital images are easy to examine, store, and share.

Figure 3. Digital images can be analyzed using colors.

Sensitivity Matters withComputed RadiographyThe sensitivity level matters with computedradiography (Figure 2). Sensitivity ismeasured in microns (µm), or 1 millionth of a meter, in both the imaging plates andthe scanner that creates the image. It is aphysical measurement of width for eachpixel on the image. Most weld-qualitysystems measure in the range of 50 to 100 µm, or 0.00005 to 0.0001 m. We usethis same measurement for film, but filmrequires no attention to microns. The reasonbeing is that the grain size is set. You canadjust the grain size by switching film, butthat is the only adjustment. Computedradiography allows you to adjust micron sizein multiple ways, ways we could neveradjust with film (Figure 3).

Many technicians do not regard thisnumber as important because they do notknow what it means. Most people do notknow that the lower the number, the finerthe detail. When it comes to fineadjustments, this setting can make all thedifference. Some situations may call forthe micron settings to be as low aspossible, while other situations will yield abetter image at higher settings. In somecases, the extra noise that comes alongwith higher sensitivity can be detrimental.It depends on every possible variable youcan consider. Should you need a unit withhigh sensitivity requirements, you willneed to favor one that has those settings.These are all details that a consultantshould be able to sort out.

Portability is an ImportantConsiderationWith computed radiography, you can get asystem that is as portable as needed and thatmeets your sensitivity needs. It is importantto establish your specific needs. If theoperation is in-house but you do performfieldwork, do not limit yourself to astationary unit that is ultimately going tomake you less money. Odds are yourcompany is looking at the utilization of that

unit very closely in order to see whether itwas worth the investment.

Large scanners are impressive to clients,but small scanners can go out to do jobsthat net you more profit. If you tell yourcompany at the end of the year that youneed money to expand a program that isstill in the red, you may not get approval.On the other hand, if you tell yourcompany that the machine is always beingpulled at from all sides for work, they maybe willing to invest more money to expandon that newfound profit center. You want tohave access to the most remote inspectionswhere you would apply this technology.When you get started on applying thistechnology, you will want to try it oneverything.

Phosphor Plates areConsumablesContrary to what any salesperson tells you,phosphor plates are consumables. Youcannot continue to use them over and overwith no replacement or the quality willdegrade along with the appearance. I havebeen told by the occasional individuals thattheir plates last longer than others, and thatmay be true. Whether that is useful isanother matter (Figure 4).

It is not about how long these plates last,but how useful they are. A plate may lastthrough 300 exposures without a scratch,but the image will be degraded from thefirst exposure. The common number that Ihear is approximately 100 exposures until aplate begins to lose sensitivity. X-raymachines will shorten the life further thanthat. This means that each program needs toconsider the cost of plates the same as thecost of buying film. These resources are notpermanent and have to be renewed.

Finding the Right ConsultantYour consultant needs to be a good listener.He/she needs to listen to a walkthrough ofyour daily operations, know the materialsfor which computed radiography isrequired, understand configurations ofequipment, and just generally understand

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your operations. Ask basic questions onrequired space, equipment, and capital, buttalk more than anything. You have all ofthe information that your consultant needs,not the other way around.

You may find a consultant at an ASNTconference or in your local sectionmeetings. Those would be good places tostart. Entire businesses are built simply onconsulting, and many training facilities alsoconsult. The right fit is out there, though itmay take some hunting.

Your local computed radiographyequipment salespeople are not consultants.No matter how they plan to be on yourside, they still have a vested interest inselling to make money.

ConclusionThese are just a few of the key details tosort out for a film replacement unit. Thereare lots of other things to consider, withmeeting your clients’ needs at the top ofthe list. Your end user needs to sign off onthis technology in order for you to getpaid, so keep them in mind for the entireprocess. Ultimately, in order to dosomething, you have to find someone whohas successfully done it and knows thedetails. Hiring a consultant makes sense,but choosing the right one is important.Someone who can get you into the process

and someone who can replace your filmoperations the right way may be twodifferent people. The fact is that few peoplehave been down that road and qualityconsultations could go a long way to help. Ihave personally seen the results of good andpoor consultation and even compared it tono consultation. The differences inconsistency are huge. h

AUTHORWesley Soape: ASNT NDT Level III in RT;Hellier NDT.

REFERENCESASTM, ASTM E 2007, Standard Guide forComputed Radiography, ASTM International,West Conshohocken, Pennsylvania, 2010.

ASTM, ASTM E 2339, Standard Practice forDigital Imaging and Communication inNondestructive Evaluation (DICONDE), ASTMInternational, West Conshohocken,Pennsylvania, 2011.

ASTM, ASTM E 2738, Standard Practice forDigital Imaging and CommunicationNondestructive Evaluation (DICONDE) forComputed Radiography (CR) Test Methods,ASTM International, West Conshohocken,Pennsylvania, 2013.

ASTM, ASTM E 2445/E 2445M, StandardPractice for Qualification and Long-Term Stabilityof Computed Radiology Systems, ASTMInternational, West Conshohocken,Pennsylvania, 2014.

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Figure 4. High quality images require plates that are not degraded.