Today?s CR/DR systems seek to lower exposure. While they may require an investment, they can offer a marketing advantage, too.

Overexposure of radiation during a CR/DR (computed radiography/digital radiography) exam is often masked by the pretty image produced?unlike their predecessor, film, which appeared black with radiation overexposure. ?With CR/DR, that feedback loop is lost. Even if you overexpose by a factor of five to 10 times, you can still render an image that looks great,? said J. Anthony Seibert, PhD, FAAPM, FACR, professor of radiology at the UC Davis Medical Center in Sacramento, Calif.

In situations that are not well controlled??often when you are imaging a child,? noted Seibert?technologists must think quickly and tend to overestimate to ensure a clean, clinically useful image. The phenomenon, referred to as dose creep (or exposure creep), means what it implies: radiation dose and exposure creep up as technologists and radiologists seek better images with the first acquisition.

Radiologists don?t like noise in their images. ?Over time, we will need to train radiologists to accept a small amount of noise in an image that doesn?t affect our ability to make a diagnosis,? said Steven Don, MD, associate professor of radiology at the St Louis-based Mallinckrodt Institute of Radiology, Washington University School of Medicine; a full-time pediatric radiologist at St Louis Children?s Hospital; and head of the CR/DR committee of the Alliance for Radiation Safety in Pediatric Imaging?s Image Gently Campaign.

The CR/DR initiative represents one way in which the medical community is seeking to lower radiation dose in pediatric patients, who are more sensitive to any level of exposure. Other programs focus on standardization of dose reporting techniques and external benchmarking.

Though the efforts are primarily driven by the desire to improve the care of and outcomes for patients, the FDA?s focus on radiation provides some impetus for radiology facilities to keep dose under control. The FDA is currently most concerned with the high-dose modalities, CT, nuclear medicine, and fluoroscopes, but it may eventually turn its eye to CR/DR.

Steven Don, MD

J. Anthony Seibert, PhD, FAAPM, FACR

John Underwood

As the radiation dose has appeared on the FDA?s radar, it has also become a public concern. Hospitals can therefore benefit in many ways with the implementation of dose-reduction strategies, including safer patient care, more cost-efficient technology acquisitions, and marketing advantages. Many are upgrading as they replace systems; others are considering if the value is worth the expense now.

Trickle Down Effect

The FDA?s Initiative to Reduce Unnecessary Radiation Exposure from Medical Imaging aims to reduce the risks of radiation exposure during CT, nuclear medicine, and fluoroscopy exams by advocating two strategies: one is to make sure every exam ordered is justified; and the other is to optimize the dose in those exams that are performed. The FDA is currently focused on high-dose technologies, but many expect a trickle down effect where CR and DR will ultimately be examined as well.

Though radiography technologies deliver a dose ranging from one to three orders of magnitude below that used in CT, the modalities still expose patients to radiation and can become a problem for the seriously ill as well as the pediatric population. ?Most radiologists operate under the principle that all radiation has some risk?the less the dose, the less the risk,? Don said. Only at zero radiation is the risk also zero, a theory described by the linear threshold model.

A patient?s risk of overexposure, whether in one visit or over time, increases with the number of radiology exams ordered. ?Many of our patients are frequent fliers, meaning they return to us multiple times for initial and follow-up examinations,? said John Underwood, administrative director of radiology at the Phoenix Children?s Hospital in Arizona.

Accumulated dose is a bigger concern in pediatric patients than in adults because of children?s small size as well as their age. ?The pediatric population is more susceptible to the adverse effects of radiation than adults,? Underwood said. Their small size increases radiation?s impact on the body, while their young age gives them more time to develop cancer as a result of exposure.

Industry Organizations Explore Solutions

To justify the risk, the exam should be necessary and the information produced diagnostically relevant. ?If you can have a high benefit-to-risk ratio, you?re much better off [imaging the patient],? Seibert said.

The installation of CR and DR systems with dose-reduction technologies can help to improve this ratio. Unfortunately, in the past, each manufacturer has used its own method for tracking dose exposure, leading to some confusion in dose management. ?Some do it using the old screen-film speed class [the S number], which is inversely related to the exposure. Others do it as a measure of plate exposure directly [relative measure]. We have systems that use both,? Don said.

Systems using the S number indicate the exposure has doubled if the number is halved; for instance, the S number decreases from 200 to 100 as exposure doubles. Systems employing the relative methodology will see the dose monitoring numbers do the reverse and double with 2x exposure, from 100 to 200. ?It can be very confusing for both technologists and radiologists to know exactly what the exposure to the plate was and whether they were using the appropriate dose,? Don said. The information will also be needed to make an accurate dose adjustment.

The CR/DR committee of the Alliance?s Image Gently Campaign is working to develop a universal standard to eliminate this confusion. The Alliance represents a consortium of 13 societies in the fields of radiology, pediatrics, medical physics, and radiation safety.

The group brought together representatives from the two organizations that have developed standards for their regions, the European-based IEC and the United States-based American Association of Physicists in Medicine (AAPM), to agree to merge the two sets of guidelines into a single universal standard. Vendors are also on board with this effort. ?The vendors, I think, are all very much in agreement that they would like to have just a single unified standard so they can eliminate confusion,? Don said. The second half of the campaign will focus on user education so they implement processes that prevent dose creep.

Industry organizations are also looking to bring standardization to protocols. The Integrating the Healthcare Enterprise (IHE) has created profiles for radiation exposure monitoring. ?We want to take a universal standard everybody agrees upon and combine it with the IHE profile for digital radiography so technologists and quality assurance professionals can use that information to create their own quality assurance programs for digital radiography,? Don said.

The American College of Radiology (ACR) has undertaken the creation of a pediatric dose index registry project for DR protocols. Hospitals can then benchmark themselves against other facilities using the same or similar equipment to judge their performance. ?If you?re above the reference levels, then what that probably means is that you have either poor technology, poor techniques, or poor understanding of how to reduce dose,? Seibert said.

Hospitals Seek Upgrades

If the technology is the problem, hospitals can upgrade their equipment. Many vendors have implemented dose-reduction technologies to optimize their radiography equipment. ?You can get capabilities that would in fact lower the dose by sometimes up to a factor of two to four times compared to the older conventional-speed CR systems available in the mid-1990s,? Seibert said.

Replacing older systems with newer ones can happen naturally. Tufts Medical Center in Boston is currently in replacement mode, gradually acquiring systems that feature dose-reduction technology, according to Mike Foley, RTR, director of radiology at the center. ?We aim to get back to the same dose we had when we had film. We have found that we?ve been able to get at least a 40% dose reduction by moving to DR,? Foley said.

Phoenix Children?s Hospital is aiming to reduce dose with complementary technologies. ?This year, we have put money into our capital budget to purchase equipment, like dose readers and pediatric phantoms, that will help reduce dose, as well as technology to report dose history to the patient or family,? Underwood said.

Radiologists can do their part by accepting a little more noise?as long as it doesn?t interfere with diagnosis. Radiologist dislike for image noise has been an impediment to dose reduction and a driver of dose creep. ?Physician education will be a long-term goal,? Don said.

The aim is to balance low dose against image quality, a concept known as ALARA: as low as reasonably achievable. Radiation dose should match the desired diagnostic information. For instance, a subtle fracture will require a higher dose to image than a longitudinal study of scoliosis. ?You can still take measurements accurately with three times less dose than that needed to spot a subtle fracture,? Seibert said.

Ultimately, any low-dose strategy should not impact clinical value. ?You don?t want to miss a diagnosis, and that?s what DR brings over CR?the actual image quality is much better. If you have better quality images, then you can provide better quality service to the patient,? Foley said.

Worth the Investment

Hospitals undertaking the transition to low-dose technologies find the expense for low-dose systems is worth the cost. ?Certainly, DR is relatively expensive, but the price has come down a bit, and it?s worth the investment now,? Foley said.

Facilities that advertise their low-dose capabilities may find they have a marketing advantage. ?Like any other benchmarking process, hospitals that can say they are among the best or the lowest or the safest will always use that type of marketing to their advantage,? Don acknowledged.

Program participation, physician accreditation, dose monitoring, and positive benchmark comparisons provide good press. ?The public is going to start to look at who provides lower radiation doses because it?s out there in the media now. I think you will start seeing people use this for marketing as they did with mammography years ago,? Foley said.

It may be particularly advantageous for children?s hospitals. According to Underwood, Phoenix Children?s Hospital intends to let its population know of its intent to limit and report dose. Underwood expects more hospitals will begin to consider switching to low-dose technologies, in part because of the threat of legislation. As Underwood put it, ?Do we need big brother to flex its muscle to do what we as radiology professionals should be doing ourselves??

Renee Diiulio is a contributing writer for Axis Imaging News.