Dose Reduction in Radiology: An Industrywide Initiative
There is no more compelling story in radiology today than the urgency with which organized radiology and imaging modality vendors have come together to address the issue of dose management in radiology. Yes, more work lies ahead, and significant challenges remain—but the swiftness and decisiveness with which providers and vendors have cooperated, and their accomplishments to date, might be unprecedented in the history of the specialty. On the provider side, radiologists—worldwide—have adopted pediatric CT protocols that protect children from receiving adult-size radiation doses, under an initiative aggressively promoted by the Image Gently™ campaign. At the Image Gently Dose Summit held in St Louis, Missouri, in February 2010, the industry turned its attention to radiography and to the adoption of an international standard that will eliminate confusing and sometimes contradictory user interfaces on various acquisition devices and will smooth the way for technologists, administrators, and radiologists to monitor dose. Gregg Cretella, manager, clinical science, FUJIFILM Medical Systems USA (Stamford, Connecticut), articulates the technical progress that has been made on the radiography front thus far, the challenges that lie ahead, and the significance of these advances in an interview with Radinformatics.com. Radinformatics.com: Which organizations are involved in the initiative? Cretella: The Alliance for Radiation Safety in Pediatric Imaging (with the Image Gently campaign) was probably the number-one driver, but also included in the list of associations would be the American Society of Radiologic Technologists (ASRT), the Medical Imaging and Technology Alliance (MITA), the American Association of Physicists in Medicine (AAPM), and the American College of Radiology (ACR). All of the CR and DR vendors participated in the Image Gently Summit, and Image Gently requested that all vendors move toward and adopt the international standard for exposure index, International Electrotechnical Commission (IEC) standard 62494-1. This was supported by the AAPM, and vendors were encouraged to begin the engineering work for adopting that standard. Historically, each vendor had its own proprietary index. Sometimes, when the dose goes up, the exposure index goes up, but on other systems, when the dose goes up, the exposure index goes down. Also, the numerical values used to represent these exposure indices are usually different, vendor to vendor, so you can imagine the difficulties, in a multivendor facility, for a technologist, as he or she moves from system to system. The whole idea behind adopting the international standard is this: Regardless of the systems the technologist is operating, they would all display and present to the technologist roughly the same information. More importantly, the new IEC standard produces a deviation index. This index, provides immediate feedback to the technologist , indicating how far an exam’s exposure deviated from the facility’s established, optimum exposure conditions. If each technologist logs into the acquisition workstation when he or she needs to use it, the system should be able to provide information on which technologists are overexposing on a given exam or underexposing—thus allowing a facility, once it analyzes such data, to identify training opportunities for the technologist. Almost a year ago, all of Fujifilm’s acquisition workstations became compliant with IEC 62494-1. Industrywide, I think there’s a little ways to go. The last time I looked, there still were a few vendors who had not yet adopted the standard, but I expect they will, at some point. As this standard becomes more understood, adopted, and accepted by the market, then certainly all vendors will adopt it. Fujifilm was an early adopter, with engineering activity that preceded requests from the Image Gently campaign. Radinformatics.com: Tell us about the vendor activities underway to mitigate radiation dose at the modality and imaging IT levels? Cretella: Vendors are working very hard in developing technology and tools to improve dose efficiency or facilitate dose management. On the technology side, vendors continue to refine their detectors so that with each new release, there is the potential for reduced dose while still achieving excellent image quality, compared with detectors of a previous version. For example, on the CR front, Fujifilm offers its exclusive dual-side reading image plates, and on the DR, front we offer flat panel detectors that utilize a new approach to image capture that we call Irradiated Side Sampling. These innovative technology advances ultimately make better use of exposures with lesser amounts of x-ray information. Regarding tools, many vendors are working to provide customers with data that could facilitate any dose-management initiatives that a facility might have started. Examples of this would be actual exposure techniques used, dose area product (DAP) measurements, and the aforementioned IEC 62494-1 standard. This data is usually recorded at the acquisition workstation and then subsequently sent out to PACS or back to the RIS. In addition to these tools, Fujifilm acquisition workstations can alert the technologist in the event of less-than-optimum exposure conditions, and compile records regarding images that were rejected because of mis-exposure. . I would add that, like Fujifilm, most vendors operate internationally. Because of this, new dose-related features might be engineered into products in response to regulations that originate from many different locales, but might benefit the global imaging community. An example of this would be the recording of DAP, which is required by European regulation and supported by Fujifilm products that are available worldwide. Radinformatics.com: Are DICOM and IHE playing a role? Cretella: They are playing a huge role. When the IEC published its exposure index standard, DICOM was quick to allocate DICOM tags that allow for the population of an acquired image’s exposure index, deviation index, and target exposure index value. There also has been a significant amount of work, on the DICOM side, almost in final form, on a CR/DR Dose Structured Report, which will provide a wealth of information on the exposure technique, the exposure index, the deviation index, and the dose area product recordings, either at the image level or at the study level. DICOM is playing a very active role in ensuring that the data produced by various vendors’ CR/DR systems can be transmitted onto the network for subsequent collection and analysis. IHE generally operates to simplify and optimize for users the DICOM standards that have been implemented. Once DICOM completes the CR/DR Dose Structured Report, then we would expect IHE to become very active in promoting compliance with that standard. Radinformatics.com: Are there any remaining challenges on the provider side that need to be addressed? Cretella: In anticipation of when enough facilities are up and running with the exposure index, the ACR is piloting to extend its national Dose Index Registry (DIR), now used for CT, to collect data on CR and DR exams. I understand that naming conventions have been a problem. For instance, Fujifilm systems identify a chest exam as a chest posteroanterior (PA) in the DICOM header, but other vendors may identify it as a chest frontal. If all of these data are going to a common repository like the ACR’s DIR, sorting out that a chest PA and a chest frontal are the same thing is a remaining challenge, but I am sure that it is one that can be overcome fairly quickly. Radinformatics.com: The dose delivered by CT is so much greater than that delivered by radiography. Why does radiography present dose issues? Cretella: It started as a CT issue. CT got all of the bad press a few years ago, particularly for dose levels. That raised the consciousness of dose overall, regardless of modality. The reason for the IEC exposure index was that occasionally, there could be the risk of a higher-than-necessary dose to a patient because of the difference between vendors and their proprietary indices. Image Gently has been a big driver of this. It has done a nice job in tackling the CT side of the equation and has decided to move the focus to CR/DR to help reduce dose creep, which essentially has been tagged to CR and DR because of the very wide dynamic range of these detectors. You can overexpose them and inevitably produce a beautiful image. The standardized exposure and deviation indices will help that considerably. Vendors like Fujifilm are now looking toward developing and finalizing advanced applications that can be performed with standard radiographic equipment, but that (through changes in image acquisition and processing) produce results that could allow for a reduction of referrals to another modality, such as CT. Dual-energy subtraction and tomosynthesis are starting to gain interest in the industry as a means of performing considerably lower-dose exams, but providing some of the diagnostic content that typically could only be found in modalities like CT. If such advanced applications could eliminate 5% of the referrals to CT, then that could mean a significant dose reduction for at least 5% of some portion of the patient population. Most applications for dual energy subtraction are for chest exams, but tomosynthesis can be useful for imaging various parts of the anatomy. Radinformatics.com: Can RIS/PACS play a role in capturing this information? What needs to happen before that is a reality? Cretella: The dose-management values that come from a modality’s acquisition workstation can certainly be received and displayed on a PACS: It’s just a matter of pointing the PACS at the right DICOM tags to display the information in the overlay. Though this could provide a modest method to monitor dose-related information, the RIS is probably the better place to compile, organize, and report out such data. To that end, our medical informatics team is in the process of engineering these powerful features into Fujifilm’s Synapse RIS. Cheryl Proval is editor of Radinformatics.com.