How Gently Do You Image?

Dr. Richard ValachovicIn this month’s letter, ADEA President and CEO Dr. Rick Valachovic shares the latest news on dental school application trends and other indicators confirming that the profession remains an attractive one.

Four years ago, I used June’s Charting Progress to discuss emerging concerns surrounding the use—and potential misuse—of cone-beam computed tomography (CBCT) in dentistry. As Bernard Friedland, B.Ch., M.Sc., J.D., a colleague of mine on the faculty at the Harvard School of Dental Medicine, pointed out at the time, CBCT technology had made its way into the hands of clinicians who had only a minimal understanding of how to select patients appropriately for CBCT imaging or lacked the knowledge to interpret CBCT images correctly. Those concerns still exist, but since that time, members of the diagnostic imaging community have stepped up to address them in meaningful ways. These dental educators are working to promote the safe and appropriate use of CBCT and to reduce the total amount of radiation exposure that patients—especially children—receive from radiographs of all types during dental care.

We can achieve these objectives by following the ALARA principle. The acronym stands for “as low as reasonably achievable” and represents the idea that exposure to ionizing radiation should not exceed the minimum amount needed to produce a diagnostically useful image.

Today, leading dental associations—ADEA included—are on record supporting the use of the ALARA principle to guide diagnostic imaging. Under the auspices of The Alliance for Radiation Safety in Pediatric Imaging, of which ADEA is a member, organizations have joined together to support the Image Gently® campaign. Launched last fall, the campaign is promoting an approach to diagnostic imaging that helps limit children’s exposure to ionizing radiation in dental settings.

The campaign’s Six-Step Plan recommends the following:

  1. Select radiographs based on each individual’s need.
  2. Use the fastest image receptor possible.
  3. Collimate the X-ray beam to expose only the area of interest.
  4. Always use thyroid collars.
  5. Childsize the exposure time.
  6. Use CBCT only when essential for diagnosis and treatment planning.

The alliance also wants to ensure that every member of the imaging team knows how to determine when imaging is appropriate and how to set the appropriate exposure when imaging children.

It’s hard to quantify the exact amount of exposure reduction that would accrue to a child if all of the protocols above were followed, but researchers estimate that exposure could be reduced by as much as 90%. Even if that number overshoots the mark, it is a stark reminder that when we fail to adhere to the ALARA principle, we are exposing children to far more radiation than is needed to diagnose and treat their conditions. This exposure occurs in part because not everyone appreciates that children are not simply small adults. Children are far more sensitive to ionizing radiation than adults are, and because their life expectancies surpass the 30- to 40-year latency period during which many cancers develop, children’s risk of dying from radiation-induced cancer is three to five times higher than that of adults.

X-ray examinations used in dental practice are the most common form of ionizing radiation exposure to the head and neck, giving our community unique opportunities to reduce the amount of radiation our youngest patients receive in this region of the body. So why do so many of us fall short of the ALARA ideal?

I asked Alan Lurie, D.D.S., Ph.D., a mentor of mine at the University of Connecticut School of Dental Medicine. His response: “The risk from radiation exposure in dentistry is very small, so it is very easily dismissed when you’re looking for disease that can injure a patient badly. You slowly start to forget about the risks of the technology because the benefits are right in front of you and the risks are based on evaluation of epidemiologic data. That’s a big separation for a clinician.” Alan and I published an article on the risks and benefits of X-ray exposure in pediatric dentistry many years ago.

Alan reminded me that the tools to limit exposure have been around for a long time. Rectangular collimation was available in the 1960s, and thyroid collars have been around even longer. By the late 1970s, F-speed film was being tested. From Alan’s perspective, it is simply inexcusable that the slower D-speed film is still being manufactured. “There is no reason to use D-speed film right now, absolutely zero,” he said. “There have been numerous tests, clinical and laboratory, of the ability to diagnose caries and periodontal disease and periapical lesions on F- versus D-speed film, and F is the equal or the superior to D in every test.”

The fact that some clinical licensure exams explicitly require that pre- and post-treatment images be obtained using D-speed film also perpetuates the use of this outdated modality. The requirement is a holdover from earlier days when this film speed was the standard. As Image Gently gains traction, and more people commit to following the ALARA principle, perhaps this requirement will finally be revised. That said, change occurs slowly. It is equally possible that the elimination of live-patient licensure exams, which has gained steam in recent years, will achieve the same end first.

“I think most dentists are trying to do the right thing, especially pediatric dentists who I’ve found to be the most patient-oriented,” Alan said, “but sometimes the risk-benefit balance gets lost in the hustle and bustle of taking care of lots of people every day.”

Christos Angelopoulos, D.D.S., M.S., agreed. Christos is President of the American Academy of Oral and Maxillofacial Radiology (AAOMR). The organization, which has published position papers on the use of CBCT in implants, endodontics and other specialties, is committed to alerting people throughout the profession about when it is—and is not—appropriate to use this powerful new imaging modality.

“CBCT is such a great tool that dentists may use it without asking, ‘Can I get the same diagnostic information using something else?’” Christos told me. While no one doubts the value of CBCT as a diagnostic tool for major skeletal anomalies such as cleft palate, facial trauma, and occlusal discrepancies, he says there is no evidence to support its routine use under other circumstances.

Several years back, AAOMR collaborated with the American Association of Endodontists (AAE) to produce a position paper that introduced guidelines for the use of CBCT by that specialty. Although following guidelines is voluntary, AAE has asked for an update, slated for release later this year. The request suggests that AAE members are finding the guidelines useful. In 2014, AAOMR issued a separate position paper on the use of CBCT in orthodontics, which affects large numbers of pediatric patients. That document commends the added value of CBCT in diagnosis, but recommends avoiding its use for routine orthodontic assessment, especially when alternate modalities are available. The paper also encourages dentists to use the ALARA principle to determine whether CBCT’s benefits exceed its risks.

When it comes to CBCT, implementing the ALARA principle is easier said than done—not because doing so is technically difficult, but because so few dentists in private practice have advanced training in oral and maxillofacial radiology. Dr. Friedland suspects that in many offices, CBCT units are used with the default settings, whether or not these are appropriate for the task at hand or the patient being imaged. This practice is especially problematic in multispecialty groups, where the defaults may be set for the types of images needing the highest resolution and widest field of view, needlessly exposing many patients, and possibly staff, to excess radiation.

We all get into routines, but when scientific evidence no longer supports our practices, it’s imperative that we consider other ways of doing things. Unfortunately, changing practice habits typically takes a full generation. Are there ways to pick up the pace? Perhaps, but not necessarily.

“States could make the Image Gently practices mandatory,” Bernard suggested. “Insurance companies could decide not to reimburse for radiographs taken without rectangular collimation. These things could be relatively easily solved in many countries, but the United States is resistant to regulation.”

Christos is optimistic that dental schools, at least, will provide fertile ground for the spread of the Image Gently approach. “Dental schools are open and familiar with the requirement of having evidence behind any decision that is being made,” he pointed out, “so these guidelines should be easier to apply in a dental school environment.”

Today, customary practices around diagnostic imaging vary considerably from school to school. The Commission on Dental Accreditation standards for both dentistry and dental hygiene require that schools have policies and procedures in place for the safe use of radiographic equipment. Determining what constitutes safe use is left to each program. At Harvard, Bernard has made it his mission to set clear parameters and make sure students understand them.

“Since we acquired CBCT 10 years ago,” Bernard told me, “I tell students, ‘You don’t want the best image. You want the worst image you can get away with.’“ In other words, once a scan is of high enough quality to enable a diagnosis, the additional information is of no value. Reminding everyone that clinicians are responsible for interpreting abnormal findings on the entire image—and liable if they do not—might also encourage more careful consideration of when to image and how to limit the field of view.

Bernard also teaches his students how to reset the machine for various types of scans, a process that typically takes just a few clicks of a mouse. If this type of education were more widely dispensed—to practicing clinicians as well as to future dentists and allied dental professionals—we would start to see the ALARA principle regularly put into action.

Today’s technologies allow us to produce diagnostic images of unprecedented clarity, but we must not let our capacity to create more detailed radiographs cloud our judgment about what’s best for our patients. To image responsibly, we must base our decisions on the available evidence and ask whether more detailed radiographs will have an impact on treatment outcomes.

Fortunately, several systematic reviews looking at the use of CBCT have appeared in the last year, giving members of our community access to new evidence on which to base their imaging practices. Additional information is available on the Image Gently website, and recent American Dental Association guidance can be found on the U.S. Food and Drug Administration website.

Looking to the future, promising imaging modalities are in development that do not use radiation, but these are far from ready for clinical application. For the present, radiographic imaging remains an essential tool in our diagnostic arsenal. Our best course of action is to focus on using current imaging modalities responsibly.

“We need to encourage people to do the right thing, to make radiographs when needed and not routinely,” Christos emphasized. “That will make a huge, huge difference.”

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