Exposed: Radiation Safety in the Imaging Suite
Nationwide cumulative-dose indices, warning flags in electronic medical records (EMRs), and electronic imaging-history smart cards: All these are being called for to protect patients from excessive radiation exposure. The real advances on this hot-button issue for radiology, however, are taking place at the health-facility level, one patient at a time.
In a watershed moment in October 2009, a luminary medical center in Los Angeles, California, announced that it had completed CT brain-perfusion scans of 206 patients over a period of 18 months, during which patients mistakenly had received eight times the called-for radiation dose per scan. The incident spawned lawsuits and a flood of media attention. The news stories were kept alive when more incidents of radiation overexposure were reported at other hospitals in California and in Alabama.
Two months later, one of a pair of radiation-dose studies¹,² that appeared in the Archives of Internal Medicine estimated that as many as 29,000 patients nationwide could develop cancer from normal levels of CT-exam radiation, and that 14,500 of them could die.
Enter the FDA, which began an investigation of the overexposure events. That investigation continues, but the FDA hasn’t waited for its results to act. In February 2010, the agency announced a three-pronged initiative to control radiation exposure in patients undergoing CT, fluoroscopy, and nuclear-medicine exams. The FDA’s three attack points are promoting safe use of imaging devices, enhancing informed clinical decision making on imaging exams, and making patients aware of the risks that they face from radiation exposure during imaging.
In February, the House of Representatives held hearings during which members of Congress expressed shock at the lack of regulation of radiation exposure during clinical imaging. The National Institutes of Health (NIH) also mandated that all vendors selling imaging systems to NIH include dose-tracking technology on those machines.
At the end of March, the focus swung back to the FDA for a two-day series of meetings and seminars at which imaging-industry trade groups, manufacturers, and professional societies assessed steps that could be taken to control radiation exposure during imaging.Calls for AccreditationOne of those testifying at the March FDA panels was E. Stephen Amis Jr, MD, FACR. Amis is professor and chair of the radiology department at the Albert Einstein College of Medicine and its teaching hospital, Montefiore Medical Center, in the Bronx, New York. He is also the former chair of an ACR® Blue Ribbon Panel on Radiation Dose in Medicine. He is the current cochair of the RSNA–ACR Joint Task Force on Adult Radiation Protection.
Amis says that the risk from radiation exposure due to medical imaging is modest, but real. Since patients in the United States now undergo about 72 million CT scans per year, researchers are probably correct in estimating that 28,000 new cancers will result, he says. In 1980, he adds, only 3 million CT scans were done. CT is the major culprit in delivering high levels of radiation to patients, with some CT tests, according to news reports,³ packing a radiation punch equal to that of 400 radiography exams. Amis says, however, that some nuclear-medicine procedures and fluoroscopic exams also deliver high doses of radiation.
Amis advocates moving quickly, on the national level, to impose controls on patient exposure. The ACR is one of two major accrediting bodies providing accreditation for CT systems. “We’d like to see every CT in the United States accredited,” Amis says. “Right now, only about 40% are accredited.” He says that accreditation forces imaging providers to submit live-patient and phantom exam data to the accrediting body to confirm that systems are functioning properly.
Amis told those at the March FDA meetings that establishing a national dose-index registry, using a standardized method for calculating radiation dose for every exam, should be imposed on equipment manufacturers industry wide. The exposure data should be included in the EMR, he adds, but that should only happen with new machines, as they are developed. He says, “There’s not much enthusiasm for going backward.”
Amis notes that it’s important to develop uniform national licensing standards for radiologic technologists. “The thing that caught everybody’s attention at the FDA meetings was that there are no uniform technologist-licensure standards. A third of the states don’t have any at all,” he says.
Amis predicts standardized reporting of doses (with the results available on every machine), a dose registry, CT accreditation, and technologist licensure. “It looks as though those things are going to happen, somewhere down the line. It will come down to federal regulation. There’s just too much interest for this to go away,” he says.Adhering To ProtocolsMany health-care providers aren’t waiting for regulation, however. They’re hard at work, developing ways to limit radiation exposure immediately. One line of attack is the implementation of procedures to make certain that patients undergoing specific tests receive only the minimum radiation exposure needed to produce useful results. This dose concept is called as low as reasonably achievable (ALARA). Of course, what’s reasonable and achievable at one institution may not be deemed so at another.
At Brown University’s Alpert Medical School and Rhode Island Hospital, William Mayo-Smith, MD, and his colleagues have been working for years to develop protocols to reduce exposure from CT exams. They were among the first to do so. “The focus has been primarily on CT because it accounts for 10% of exam volumes, but 70% of dosage issues,” Mayo-Smith says.
Some protocols, such as reducing milliamperage for kidney-stone imaging, have been obvious candidates for development. “The lower dose means it’s a noisier image,” Mayo-Smith says. “Since kidney stones are bright on the CT, however, the increased noise is not a diagnostic dilemma. With CT, 20 years ago, it was one size fits all. Now, we use more sophisticated acquisition parameters to target the type of exam that’s performed to the clinical question that’s being asked. We do this by modifying the scanner parameters and protocols, tailoring them to the clinical question. The patient gets a CT, but the type that’s done varies according to clinical history.”
Over the years, Mayo-Smith and his colleagues have developed many protocols for answering specific clinical questions. “A pancreatic mass has a different protocol than appendicitis, and that’s different from a kidney stone, which is different from a kidney mass, which is different from a hematoma or blood in the urine,” he says.
The Rhode Island Hospital team also tries to limit scans to the body parts being examined. This, Mayo-Smith says, prevents image creep—in which, for example, the upper abdomen could be included in an exam requested to evaluate the chest for a pulmonary embolism. “In general, we now image only the area in question, being careful not to scan other regions adjacent to it,” he explains. “We also use breast shielding, which decreases dose to breast tissue.” All the hospital’s protocols are preloaded into the scanners. When the clinical information comes in with an imaging order, the radiologist prescribes the protocol, Mayo-Smith says. The technologists carry out those directions. “We run 24/7, with over 35 technologists using the standardized protocols,” he says.
“Google CT protocols, and our site comes up; these protocols were years in the making, and it’s an ongoing process,” Mayo-Smith says, noting that the Alpert Medical School’s detailed protocols are available to referring physicians anywhere in the world.
Since children are at more risk from radiation than adults are, Mayo-Smith credits pediatric radiologists with spearheading the concern over radiation exposure. Manufacturers have also responded by making machines with automatic exposure controls that limit radiation based on the size of the body part being examined. In addition, new postprocessing reconstruction techniques that require less radiation to generate a picture are in the development pipeline.
“The risk for cancer induction from radiation is not well sorted out, and it’s controversial,” Mayo-Smith says. “We do know that kids are at higher risk than adults. We know, at very high radiation, the incidence of cancer is higher, but is there cancer risk from the scans being done? That’s the question. The best way to proceed, until we know more, is to adopt ALARA techniques.”
Other important elements are to make sure that the exam being ordered is truly indicated, that there are not substitute exams without radiation (particularly in the younger patient population), and that the patient has not had the exam performed recently at another institution, Mayo-Smith says. “We have developed a computer program that searches our database for prior exams performed at the three hospitals within our parent network,” he says. “This will alert the referring physician that a CT exam may have been performed in the recent past.”Risk FlagsSteven C. Birnbaum, MD, is taking another (and quite elemental) avenue toward heading off excessive exposure. Birnbaum interprets studies at the Southern New Hampshire Medical Center in Nashua. He is also a staff radiologist and radiation-safety officer at the Parkland Medical Center in nearby Derry.
“I had seen the risk of cancer death the FDA was quoting on CT, which was one in 2,000 for an exam of the abdomen or pelvis. I had also read that the risk of death from a contrast allergy was one in 250,000 injections. I thought, ‘There’s much more of an issue with CT,’” Birnbaum says.
He also had a strong personal motive for pursuing reduced exposure from CT scans. In 2005, his daughter, Molly (then 22 years old), suffered multiple fractures and soft-tissue injuries in a car accident.
“When she came in with severe trauma, she was CT scanned from head to toe, which was entirely appropriate. On day two, though, she was still in the ICU, and they thought her blood count was down because the blood had been drawn from the wrong arm, so they sent her down for another CT to see if the fluid in the belly was changing,” Birnbaum says. Before her treatment concluded, she’d had a total of nine CT exams. “Some of the follow-up studies were absurd,” Birnbaum says.
He also saw a case in which a patient was given 34 CT scans “before we put a stop to it. Every practice has cases like that,” he says. “CT is a wonderful test. I can’t do what I do without it. I’m not anti-CT,” he makes clear.
He notes, however, that in New Hampshire, the limit for incidental exposure for workers in radioactive settings (such as those who handle radiopharmaceuticals) is 50 mSv over a lifetime. “I’m looking at 50 mSv for five CT studies of the abdomen, yet a worker with 50 mSv can get taken off the line. Patients get 300 mSv exposures, and more, regularly,” Birnbaum says. Regulators need to broaden their focus to include not just workers, but patients. “That’s where the action is,” he says.
To take action himself, following his daughter’s experience, Birnbaum devised a conversion of an existing contrast-agent allergy flagging technology in the RIS to flag patients who had undergone five or more CT exams. The flags were used only in selected CT-exam categories: abdomen, neck, chest, and pelvis. To be flagged, the patients had to be younger than 40 and cancer free.
“You just add it in the RIS like a flag that someone is allergic to penicillin,” Birnbaum says. “We started that 2.5 years ago. We’ve had about 75 patients flagged since then, and we did no CT in about 30% of those patients. About half of the exams were cancelled, and the other half were switched to other modalities.” Technologists are vital to the process, he says. They see the flag when an exam is ordered; they call in the radiologists and direct them to the referring physicians.
Birnbaum is careful to explain that the flag is based on numbers of CT exams only, not on estimated cumulative exposure from those exams. In fact, he says, accurately measuring cumulative radiation exposure is extremely difficult.
“You can’t use the estimates in the literature. Those are gross estimates, probably plus or minus 40%. A 10-mSv exam could really be 5 or 15 mSv. To find the actual exposure, you have to do it patient by patient. With my five exams (for a flag), I get an estimate. I do check the dose–length product values on the machine to make sure I’m not getting overexposure,” he says.Changing ExamsLinda B. Haramati, MD, MS, is division head of cardiothoracic radiology at Montefiore Medical Center and a radiology professor at the Albert Einstein College of Medicine. In 2006 and 2007, Haramati was part of a team that demonstrated that radiation exposure can be reduced, for emergency-department patients with suspected pulmonary embolism, by relying on a simple algorithm to route some patients to ventilation/perfusion scans rather than to CT pulmonary angiography (CTPA).
Haramati says that ventilation/perfusion scans, which were preferred for suspected pulmonary embolism before CTPA became common, can reduce radiation exposure to the breasts of female patients. Radiation delivered to the breasts is 20 to 40 times greater for CTPA than for ventilation/perfusion scanning, she says, but many physicians aren’t aware of that.
The algorithm employed to select patients for ventilation/perfusion scanning is simple. If emergency-department physicians suspect pulmonary embolism, a chest radiograph is taken. If that is normal, the patient is routed to ventilation/perfusion testing. If the radiograph shows lung/pleural disease, the patient is sent for CTPA.
In the study4 of the algorithm, the number of CTPA patients decreased from 1,234 in 2006 to 920 in 2007. The number of patients undergoing ventilation/perfusion scanning increased from 745 to 1,216 over the same span. Overall, the mean effective radiation dose was reduced by 20%.
“In 2006, between 35% and 40% of the tests were ventilation/perfusion scans and 60% to 65% were CT. By the end of the last quarter of 2007, we had 40% CT and 60% ventilation/perfusion scanning,” Haramati says. “It reversed.”
She points out, however, that Montefiore Medical Center’s radiology and nuclear-medicine departments are separate, but work collaboratively. “One of the things we were criticized for was that about 40% of our pulmonary-embolism imaging was ventilation/perfusion scanning before we did the study, which is high. It’s normally an uncommon test, used only for patients who can’t get a CT,” she says.
Nonetheless, the 20% reduction in radiation exposure took place even with the high rates of ventilation/perfusion scanning, she says, adding that the test is underutilized at many institutions. Montefiore Medical Center does imaging for about 2,000 pulmonary-embolism cases per year, Haramati adds. “Pulmonary embolism imaging is a pretty big business. It’s a common indication for CT of the chest,” she says.
Haramati also points out what she calls indication creep for CTPA. “When we first started, the results were about 20% positive. Now, they are 5% or 6% positive, which means they’re doing a lot of cases with lower and lower suspicion of disease.” That mirrors radiology generally; she says, “Pulmonary-embolism imaging is part of the radiology growth picture.”
In a recently completed study,5 Haramati and her fellow researchers at Montefiore Medical Center retrospectively studied imaging in patients with hydrocephalus, renal colic, pulmonary embolism, and heart disease; they found that in all categories, patients imaged from 2000 to 2005 had less radiation exposure than those imaged from 2005 to 2007. “That’s because there’s more and more imaging being done,” Haramati says. “This goes along with what we’ve seen in the rest of the world.”Quality ImprovementA consortium of Michigan hospitals is applying radiation-reduction protocols on a broad front and using a registry to track the effectiveness of its quality-improvement program. So far, according to Gilbert L. Raff, MD, FACC, the effort is paying big dividends, with multihospital exposure reductions, for some imaging procedures, of more than 50%.
Raff, a cardiologist, is medical director for the Ministrelli Center for Advanced Cardiovascular CT Research at Beaumont Hospital in Royal Oak, Michigan. The hospital is a participant in a consortium of Michigan hospitals organized under the aegis of regional health-insurance carriers to use patient registries to track and improve health-care outcomes.
Raff is also chair of the research committee of the Society of Cardiovascular Computed Tomography. He has been a key participant in leading the Michigan consortium’s effort to lower radiation exposures for patients undergoing coronary CT angiography (CCTA).
Starting with 16 hospitals in its registry, the consortium found, initially, that its median radiation dose for CCTA was about 21 mSv (far higher than the expected dose, based on the research literature, of 13 to 16 mSv), Raff says. Even accounting for the fact the Michigan figures included some preparatory imaging not included in the published studies, the exposure levels were too high.
The hospitals reacted by applying simple-dose reduction protocols. A year later, the CCTA dose for the 16 consortium hospitals had been cut by more than half, to a median of 9.8 mSv. Raff says, “We had a team that helped the hospitals; experts on the scanners worked with the radiology supervisors to work through the best methods at each site. We recently sent in data that showed, 18 months later, that the doses were still sustained in the 9.9-mSv range. You don’t retrain, but there is monthly feedback, and the doses have stayed down; it’s pretty exciting that the lower doses were sustained.”
To get the doses down, the Michigan hospitals employed a three-step process. The first step was preparing the patients by using beta-blockers to lower heart rate, allowing high-voltage radiation to be applied over a much shorter time interval. Raff says, “That reduces the dose. With a faster heart rate, you’re not sure exactly where you’re going to get a good picture, so you have to leave the machine on for most of diastole. That gives the patient twice as much radiation.”
The second element that the consortium hospitals focused on with CCTA was body-mass index (BMI). “We start CCTA with 120 kV, but with a BMI of 30 or less, you can get by with 100 (which, in absorbed radiation, is a reduction of 40%),” Raff says. The third thing that the consortium hospitals did to cut radiation dose was to avoid image creep by focusing on the heart. This can cut exposure by 10% to 20%, Raff says.
Raff adds that the dose registry and the protocols developed for CCTA have changed the culture, within the consortium’s member hospitals, concerning radiation exposure. The consortium has now expanded to 53 hospitals, and when new hospitals come in, their CCTA exposure values are around 15 mSv, as opposed to around 25 mSv in the beginning, Raff says. “I know it’s better; I don’t have a handle on things outside Michigan. The methodologies are really not very difficult. I’m pretty confident this approach will work its way through all the CT procedures,” he says.
To Raff, it makes sense to track cumulative exposure per patient. “I hope that’s through a credit-card type of thing or a network medical record, but that requires a change,” he says. “That’s the sort of thing that health-care reform is supposed to be delivering.”
Raff says that he’s already seen evidence that the newest CT scanners will make drastic reductions in radiation dose. “There are some producing scans in the 4- to 5-mSv range, and some as low as 1 to 2 mSv. These are not yet widely available, but we have one, and it really does the job,” he says.
The Michigan consortium is, in fact, planning a study in which it will take data from older scanners for certain procedures and compare exposure and image quality to the same attributes (for the same number of procedures) from new machines.
“The new scanners may be more challenging because those are huge reductions in dose. Some are 90% reductions, but I’ve seen some artifacts from that,” Raff says. “We may be better off with 50% or 60% reductions in dose. It’s a cost–benefit ratio. In the end, we’ll have to see what happens.”Physicists and CTWalter Huda, PhD, FCCPM/ABMP, is a medical physicist and a professor of radiology in the physics division of the Department of Radiology and Radiological Science at the Medical University of South Carolina in Charleston.
Huda believes that radiologists bear the ultimate responsibility for ensuring that patients are not systematically receiving inappropriate doses of radiation. He says that manufacturers usually have default parameters for radiation exposure in place on imaging systems, but that radiologists and technologists will sometimes tinker with them. “It’s a hodgepodge arrangement,” he says, adding that those who are uncertain should consult ACR guidelines for diagnostic reference levels.
“Every time they scan a patient, there is a dose-summary sheet on that patient that can be sent to PACS. I put the primary responsibility on the radiologists,” Huda says. Radiologists need to keep an eye on the dose summaries, he adds.
Huda says that physicists have the job of helping to optimize protocols by adjusting voltage, tube rotation, scanning speed, and the like, but he maintains that the problem of radiation exposure to is quite solvable.
“Radiation exposure carries small (but nonzero) risks,” he says, “but what to do is easy. Apply two rules: One, never expose a patient to radiation unless there is a bigger benefit to the patient than the risk from exposure; two, when performing an exam, never use more radiation than needed—ALARA, in other words. If you make a decision, you need to be knowledgeable and to understand the benefits and risks. It’s a judgment call, but one being made by a knowledgeable, board-certified individual.”
Physicists also analyze the risks associated with various exam protocols. Huda says, “I recently did a study6 on cardiac CTA. I showed that the average risk of developing cancer was 1 in 1,000. The high risk was for the lung, not the breast, even though the breasts got most of the radiation. Sensitivity of the patient was a factor, too.”
Huda says that the automated exposure controls that manufacturers are putting on the latest systems are a promising development. With this technology, the scanner can adjust radiation exposure for different parts of the body during a scan. Moving over the breasts, it will shift focus and reduce exposure, Huda says. It will also vary exposure according to body parts’ mass. “It’s the most dose-saving method, and it doesn’t subtract from diagnostic performance,” Huda says.
Huda is planning a study to show how much automated exposure controls can reduce radiation to the breasts, particularly in younger females. “It might be a 5% to 50% reduction,” he says. “My guesstimate is 35% to 50%.”
Whether or not radiology departments can rely automatically on dose-limiting software was called into question when a report in the New York Times7 blamed overradiation incidents at two sites on dose-limiting software that may have contributed to overexposure. Unlike the breast-dose–saving software referred to by Huda, the software program in question is related to a noise index and is proprietary.
J. Anthony Seibert, PhD, president-elect of the Association of Physicists in Medicine and professor of diagnostic imaging physics at the University of California–Davis, speculates that the overexposures could have been the result of an unreasonably low setting of the noise index that caused the milliamperage to max out at eight times the optimal dose. The result is that now, everyone has a better understanding of the significance of the volume CT dose index.
“The technology is outstripping the trainer’s ability to train and the learner’s ability to learn,” Seibert notes. “We, collectively—not just the manufacturers, but the receivers of the information—do not do enough or pay enough attention, in terms of commissioning a piece of equipment, the impact of what these values mean, the potential hazardous use of the equipment, and untoward outcomes that can occur in the use of the equipment.”
Mayo-Smith advises ongoing vigilance. “It is very important that radiology departments create a team approach to reviewing CT protocols for dose parameters, to make sure protocols are created not only to optimize image quality, but to minimize dose,” he notes. “This is an ongoing process, particularly as new indications for CT examinations are created and new protocols are developed.” He recommends that the team include a radiologist, a physicist, and a lead technologist.
Huda is not a fan of attempting to collect cumulative dose information on patients. If radiologists are following ALARA and risk–benefit judgments, he asks what the point would be. “For the cumulative effect of indicated exams, I don’t see any value in adding up the radiation,” he says.
Of course, the fact that a patient has had multiple CT exams might figure into the risk–benefit decision on ensuing scans. That’s one reason that Huda calls for the exposure summary on every exam to be dictated from the PACS when a radiologist completes a report, along with a notation that the exposure level produced (or failed to produce) a readable image. That way, instances of using too much or too little exposure to yield a readable exam can be tracked as well. “I’m in the process of doing that at my institution,” Huda says.Dose TrackingGeorge Shih, MD, is assistant professor of radiology at Weill Cornell Medical College, New York, New York. He is also a computer enthusiast. Working with a team of medical physicists at Columbia University, Shih has come up with a system for tracking CT radiation exposure for inpatients that he believes can be extrapolated to radiology in general. Shih calls his system Valkyrie.
Valkyrie, Shih says, has extracted CT radiation exposure data, so far, with 100% accuracy. On newer machines, it takes the data directly from the scanner, but on older machines, where there are no scanner data, it relies on “text embedded in the images—CT screenshots,” Shih says. He adds that his team was able to use connected components to extract the exposures from the screenshots.
Valkyrie is still in a nascent stage, Shih says. It’s not patented, and it’s only available for Weill Cornell inpatients, but for them, it works. It automatically records—on what is now a stand-alone server—the exam exposures (based on manufacturers’ estimates using phantoms), and it adjusts those figures based on the patient’s actual size and weight. If Valkyrie sees excessive exposures, it automatically contacts radiologists by email so that the problem can be corrected at once, Shih says.
“Immediately, there are people alerted,” Shih says. He admits this hasn’t happened yet in a real setting because only three scanners are connected to the system, and it’s new. Any overexposure not caught before the first exam, however, should be caught thereafter, preventing more excessive exposures. “We’ve had nothing adverse yet, but we’re ready if something happens,” Shih says.
Another advantage of Valkyrie is that it could be used retrospectively to extract exposure data from any PACS archive. That might lead to a better understanding of health-care–related radiation exposure, Shih says. For now, though, Shih is satisfied to have a new quality-control tool, which might or might not have a commercial or industry-wide application.Dose RegulationAt the March meetings called by the FDA, the major powers in the imaging industry—scanner manufacturers, medical societies, and government agencies—all lined up behind the principle of reducing radiation exposure, despite a lack of proof that widespread cancer increases will result from imaging being done as it is now. Better safe than sorry was a major theme.
Today, however, there is no regulatory body charged with making certain that radiation exposure limits are applied or enforced. Only four states require medical physicists to be licensed, and many states have yet to license radiologic technologists. Who will take the lead in further regulation, if there is any, is unclear. Some call for the federal government to step in; some want the states to take charge.
Alberto Gutierrez, PhD, is director of the Office of In Vitro Diagnostics at the FDA’s Center for Devices and Radiological Health. Trained as a chemist, Gutierrez is now charged with overseeing imaging-device radiation safety for the FDA. The FDA’s essential role, he says, is clearing scanners and other devices for safe use.
“We can require the manufacturers to put in safeguards, if we believe they’re necessary for a safe and effective manner of operation,” he says. “We can make sure manufacturers put alerts on the machines and keep records. We can require checkers on dosage and alarms if procedures go beyond a certain amount of radiation. The manufacturers have agreed on putting in appropriate alerts.”
What the FDA can’t do, Gutierrez says, is monitor the practice of medicine in hospitals and clinics where imaging techniques are put into play. “We can do things like clear safeguards with CMS,” to make sure that the machines are used correctly, he says. “We do play a role in that area. We partner with CMS to keep up quality-assurance practices for imaging facilities and hospitals.”
Now, he adds, the FDA is meeting with industry and medical-society representatives to “talk about how to establish a national dose registry and diagnostic reference levels,” he says. Gutierrez adds, “There’s a good chance the FDA will work on guidance documents and continue careful monitoring of all the manufacturers on whether we are seeing more radiation overexposures, and if we are, we will continue to bring those to the attention of the manufacturers and the medical community to determine what needs to be done.”
When it comes to regulation, Gutierrez takes a softer stance. “From the exposure events that we have seen, we don’t believe that this is an area in which we would need to change regulations, or where the manufacturers did something wrong, per se,” he says.
The FDA is unlikely to seek a regulatory role for itself; Gutierrez says, “National regulation is not our purview.” Nonetheless, the days when imaging facilities and hospitals could proceed as usual, while patients’ exposure to radiation grew in company with exam volumes and the number of CT detectors, appear to be gone.
The California legislature is proving the point. The California Senate recently passed SB 1237, which would, beginning in 2012, require—if technologically feasible—health facilities and clinics to record the dose of radiation received by a patient during a CT scan and input that dose as part of the patient’s medical record. The bill is now being considered by the California Assembly. Compliance for rural providers would be delayed until 2013. Accreditation of high-end imaging providers would also be mandated. The California Department of Public Health would have regulatory control. George Wiley is a contributing writer for Radiology Business Journal.
Amis predicts standardized reporting of doses (with the results available on every machine), a dose registry, CT accreditation, and technologist licensure. “It looks as though those things are going to happen, somewhere down the line. It will come down to federal regulation. There’s just too much interest for this to go away,” he says.Adhering To ProtocolsMany health-care providers aren’t waiting for regulation, however. They’re hard at work, developing ways to limit radiation exposure immediately. One line of attack is the implementation of procedures to make certain that patients undergoing specific tests receive only the minimum radiation exposure needed to produce useful results. This dose concept is called as low as reasonably achievable (ALARA). Of course, what’s reasonable and achievable at one institution may not be deemed so at another.
At Brown University’s Alpert Medical School and Rhode Island Hospital, William Mayo-Smith, MD, and his colleagues have been working for years to develop protocols to reduce exposure from CT exams. They were among the first to do so. “The focus has been primarily on CT because it accounts for 10% of exam volumes, but 70% of dosage issues,” Mayo-Smith says.
Some protocols, such as reducing milliamperage for kidney-stone imaging, have been obvious candidates for development. “The lower dose means it’s a noisier image,” Mayo-Smith says. “Since kidney stones are bright on the CT, however, the increased noise is not a diagnostic dilemma. With CT, 20 years ago, it was one size fits all. Now, we use more sophisticated acquisition parameters to target the type of exam that’s performed to the clinical question that’s being asked. We do this by modifying the scanner parameters and protocols, tailoring them to the clinical question. The patient gets a CT, but the type that’s done varies according to clinical history.”Over the years, Mayo-Smith and his colleagues have developed many protocols for answering specific clinical questions. “A pancreatic mass has a different protocol than appendicitis, and that’s different from a kidney stone, which is different from a kidney mass, which is different from a hematoma or blood in the urine,” he says.
The Rhode Island Hospital team also tries to limit scans to the body parts being examined. This, Mayo-Smith says, prevents image creep—in which, for example, the upper abdomen could be included in an exam requested to evaluate the chest for a pulmonary embolism. “In general, we now image only the area in question, being careful not to scan other regions adjacent to it,” he explains. “We also use breast shielding, which decreases dose to breast tissue.” All the hospital’s protocols are preloaded into the scanners. When the clinical information comes in with an imaging order, the radiologist prescribes the protocol, Mayo-Smith says. The technologists carry out those directions. “We run 24/7, with over 35 technologists using the standardized protocols,” he says.
“Google CT protocols, and our site comes up; these protocols were years in the making, and it’s an ongoing process,” Mayo-Smith says, noting that the Alpert Medical School’s detailed protocols are available to referring physicians anywhere in the world.
Since children are at more risk from radiation than adults are, Mayo-Smith credits pediatric radiologists with spearheading the concern over radiation exposure. Manufacturers have also responded by making machines with automatic exposure controls that limit radiation based on the size of the body part being examined. In addition, new postprocessing reconstruction techniques that require less radiation to generate a picture are in the development pipeline.
“The risk for cancer induction from radiation is not well sorted out, and it’s controversial,” Mayo-Smith says. “We do know that kids are at higher risk than adults. We know, at very high radiation, the incidence of cancer is higher, but is there cancer risk from the scans being done? That’s the question. The best way to proceed, until we know more, is to adopt ALARA techniques.”
Other important elements are to make sure that the exam being ordered is truly indicated, that there are not substitute exams without radiation (particularly in the younger patient population), and that the patient has not had the exam performed recently at another institution, Mayo-Smith says. “We have developed a computer program that searches our database for prior exams performed at the three hospitals within our parent network,” he says. “This will alert the referring physician that a CT exam may have been performed in the recent past.”Risk FlagsSteven C. Birnbaum, MD, is taking another (and quite elemental) avenue toward heading off excessive exposure. Birnbaum interprets studies at the Southern New Hampshire Medical Center in Nashua. He is also a staff radiologist and radiation-safety officer at the Parkland Medical Center in nearby Derry.
“I had seen the risk of cancer death the FDA was quoting on CT, which was one in 2,000 for an exam of the abdomen or pelvis. I had also read that the risk of death from a contrast allergy was one in 250,000 injections. I thought, ‘There’s much more of an issue with CT,’” Birnbaum says.
He also had a strong personal motive for pursuing reduced exposure from CT scans. In 2005, his daughter, Molly (then 22 years old), suffered multiple fractures and soft-tissue injuries in a car accident.
“When she came in with severe trauma, she was CT scanned from head to toe, which was entirely appropriate. On day two, though, she was still in the ICU, and they thought her blood count was down because the blood had been drawn from the wrong arm, so they sent her down for another CT to see if the fluid in the belly was changing,” Birnbaum says. Before her treatment concluded, she’d had a total of nine CT exams. “Some of the follow-up studies were absurd,” Birnbaum says.
He also saw a case in which a patient was given 34 CT scans “before we put a stop to it. Every practice has cases like that,” he says. “CT is a wonderful test. I can’t do what I do without it. I’m not anti-CT,” he makes clear.
He notes, however, that in New Hampshire, the limit for incidental exposure for workers in radioactive settings (such as those who handle radiopharmaceuticals) is 50 mSv over a lifetime. “I’m looking at 50 mSv for five CT studies of the abdomen, yet a worker with 50 mSv can get taken off the line. Patients get 300 mSv exposures, and more, regularly,” Birnbaum says. Regulators need to broaden their focus to include not just workers, but patients. “That’s where the action is,” he says.
To take action himself, following his daughter’s experience, Birnbaum devised a conversion of an existing contrast-agent allergy flagging technology in the RIS to flag patients who had undergone five or more CT exams. The flags were used only in selected CT-exam categories: abdomen, neck, chest, and pelvis. To be flagged, the patients had to be younger than 40 and cancer free.
“You just add it in the RIS like a flag that someone is allergic to penicillin,” Birnbaum says. “We started that 2.5 years ago. We’ve had about 75 patients flagged since then, and we did no CT in about 30% of those patients. About half of the exams were cancelled, and the other half were switched to other modalities.” Technologists are vital to the process, he says. They see the flag when an exam is ordered; they call in the radiologists and direct them to the referring physicians.
Birnbaum is careful to explain that the flag is based on numbers of CT exams only, not on estimated cumulative exposure from those exams. In fact, he says, accurately measuring cumulative radiation exposure is extremely difficult.
“You can’t use the estimates in the literature. Those are gross estimates, probably plus or minus 40%. A 10-mSv exam could really be 5 or 15 mSv. To find the actual exposure, you have to do it patient by patient. With my five exams (for a flag), I get an estimate. I do check the dose–length product values on the machine to make sure I’m not getting overexposure,” he says.Changing ExamsLinda B. Haramati, MD, MS, is division head of cardiothoracic radiology at Montefiore Medical Center and a radiology professor at the Albert Einstein College of Medicine. In 2006 and 2007, Haramati was part of a team that demonstrated that radiation exposure can be reduced, for emergency-department patients with suspected pulmonary embolism, by relying on a simple algorithm to route some patients to ventilation/perfusion scans rather than to CT pulmonary angiography (CTPA).
Haramati says that ventilation/perfusion scans, which were preferred for suspected pulmonary embolism before CTPA became common, can reduce radiation exposure to the breasts of female patients. Radiation delivered to the breasts is 20 to 40 times greater for CTPA than for ventilation/perfusion scanning, she says, but many physicians aren’t aware of that.
The algorithm employed to select patients for ventilation/perfusion scanning is simple. If emergency-department physicians suspect pulmonary embolism, a chest radiograph is taken. If that is normal, the patient is routed to ventilation/perfusion testing. If the radiograph shows lung/pleural disease, the patient is sent for CTPA.
In the study4 of the algorithm, the number of CTPA patients decreased from 1,234 in 2006 to 920 in 2007. The number of patients undergoing ventilation/perfusion scanning increased from 745 to 1,216 over the same span. Overall, the mean effective radiation dose was reduced by 20%.
“In 2006, between 35% and 40% of the tests were ventilation/perfusion scans and 60% to 65% were CT. By the end of the last quarter of 2007, we had 40% CT and 60% ventilation/perfusion scanning,” Haramati says. “It reversed.”
She points out, however, that Montefiore Medical Center’s radiology and nuclear-medicine departments are separate, but work collaboratively. “One of the things we were criticized for was that about 40% of our pulmonary-embolism imaging was ventilation/perfusion scanning before we did the study, which is high. It’s normally an uncommon test, used only for patients who can’t get a CT,” she says.
Nonetheless, the 20% reduction in radiation exposure took place even with the high rates of ventilation/perfusion scanning, she says, adding that the test is underutilized at many institutions. Montefiore Medical Center does imaging for about 2,000 pulmonary-embolism cases per year, Haramati adds. “Pulmonary embolism imaging is a pretty big business. It’s a common indication for CT of the chest,” she says.
Haramati also points out what she calls indication creep for CTPA. “When we first started, the results were about 20% positive. Now, they are 5% or 6% positive, which means they’re doing a lot of cases with lower and lower suspicion of disease.” That mirrors radiology generally; she says, “Pulmonary-embolism imaging is part of the radiology growth picture.”
In a recently completed study,5 Haramati and her fellow researchers at Montefiore Medical Center retrospectively studied imaging in patients with hydrocephalus, renal colic, pulmonary embolism, and heart disease; they found that in all categories, patients imaged from 2000 to 2005 had less radiation exposure than those imaged from 2005 to 2007. “That’s because there’s more and more imaging being done,” Haramati says. “This goes along with what we’ve seen in the rest of the world.”Quality ImprovementA consortium of Michigan hospitals is applying radiation-reduction protocols on a broad front and using a registry to track the effectiveness of its quality-improvement program. So far, according to Gilbert L. Raff, MD, FACC, the effort is paying big dividends, with multihospital exposure reductions, for some imaging procedures, of more than 50%.
Raff, a cardiologist, is medical director for the Ministrelli Center for Advanced Cardiovascular CT Research at Beaumont Hospital in Royal Oak, Michigan. The hospital is a participant in a consortium of Michigan hospitals organized under the aegis of regional health-insurance carriers to use patient registries to track and improve health-care outcomes.
Raff is also chair of the research committee of the Society of Cardiovascular Computed Tomography. He has been a key participant in leading the Michigan consortium’s effort to lower radiation exposures for patients undergoing coronary CT angiography (CCTA).
Starting with 16 hospitals in its registry, the consortium found, initially, that its median radiation dose for CCTA was about 21 mSv (far higher than the expected dose, based on the research literature, of 13 to 16 mSv), Raff says. Even accounting for the fact the Michigan figures included some preparatory imaging not included in the published studies, the exposure levels were too high.
The hospitals reacted by applying simple-dose reduction protocols. A year later, the CCTA dose for the 16 consortium hospitals had been cut by more than half, to a median of 9.8 mSv. Raff says, “We had a team that helped the hospitals; experts on the scanners worked with the radiology supervisors to work through the best methods at each site. We recently sent in data that showed, 18 months later, that the doses were still sustained in the 9.9-mSv range. You don’t retrain, but there is monthly feedback, and the doses have stayed down; it’s pretty exciting that the lower doses were sustained.”
To get the doses down, the Michigan hospitals employed a three-step process. The first step was preparing the patients by using beta-blockers to lower heart rate, allowing high-voltage radiation to be applied over a much shorter time interval. Raff says, “That reduces the dose. With a faster heart rate, you’re not sure exactly where you’re going to get a good picture, so you have to leave the machine on for most of diastole. That gives the patient twice as much radiation.”
The second element that the consortium hospitals focused on with CCTA was body-mass index (BMI). “We start CCTA with 120 kV, but with a BMI of 30 or less, you can get by with 100 (which, in absorbed radiation, is a reduction of 40%),” Raff says. The third thing that the consortium hospitals did to cut radiation dose was to avoid image creep by focusing on the heart. This can cut exposure by 10% to 20%, Raff says.
Raff adds that the dose registry and the protocols developed for CCTA have changed the culture, within the consortium’s member hospitals, concerning radiation exposure. The consortium has now expanded to 53 hospitals, and when new hospitals come in, their CCTA exposure values are around 15 mSv, as opposed to around 25 mSv in the beginning, Raff says. “I know it’s better; I don’t have a handle on things outside Michigan. The methodologies are really not very difficult. I’m pretty confident this approach will work its way through all the CT procedures,” he says.
To Raff, it makes sense to track cumulative exposure per patient. “I hope that’s through a credit-card type of thing or a network medical record, but that requires a change,” he says. “That’s the sort of thing that health-care reform is supposed to be delivering.”
Raff says that he’s already seen evidence that the newest CT scanners will make drastic reductions in radiation dose. “There are some producing scans in the 4- to 5-mSv range, and some as low as 1 to 2 mSv. These are not yet widely available, but we have one, and it really does the job,” he says.
The Michigan consortium is, in fact, planning a study in which it will take data from older scanners for certain procedures and compare exposure and image quality to the same attributes (for the same number of procedures) from new machines.
“The new scanners may be more challenging because those are huge reductions in dose. Some are 90% reductions, but I’ve seen some artifacts from that,” Raff says. “We may be better off with 50% or 60% reductions in dose. It’s a cost–benefit ratio. In the end, we’ll have to see what happens.”Physicists and CTWalter Huda, PhD, FCCPM/ABMP, is a medical physicist and a professor of radiology in the physics division of the Department of Radiology and Radiological Science at the Medical University of South Carolina in Charleston.
Huda believes that radiologists bear the ultimate responsibility for ensuring that patients are not systematically receiving inappropriate doses of radiation. He says that manufacturers usually have default parameters for radiation exposure in place on imaging systems, but that radiologists and technologists will sometimes tinker with them. “It’s a hodgepodge arrangement,” he says, adding that those who are uncertain should consult ACR guidelines for diagnostic reference levels.
“Every time they scan a patient, there is a dose-summary sheet on that patient that can be sent to PACS. I put the primary responsibility on the radiologists,” Huda says. Radiologists need to keep an eye on the dose summaries, he adds.
Huda says that physicists have the job of helping to optimize protocols by adjusting voltage, tube rotation, scanning speed, and the like, but he maintains that the problem of radiation exposure to is quite solvable.
“Radiation exposure carries small (but nonzero) risks,” he says, “but what to do is easy. Apply two rules: One, never expose a patient to radiation unless there is a bigger benefit to the patient than the risk from exposure; two, when performing an exam, never use more radiation than needed—ALARA, in other words. If you make a decision, you need to be knowledgeable and to understand the benefits and risks. It’s a judgment call, but one being made by a knowledgeable, board-certified individual.”
Physicists also analyze the risks associated with various exam protocols. Huda says, “I recently did a study6 on cardiac CTA. I showed that the average risk of developing cancer was 1 in 1,000. The high risk was for the lung, not the breast, even though the breasts got most of the radiation. Sensitivity of the patient was a factor, too.”
Huda says that the automated exposure controls that manufacturers are putting on the latest systems are a promising development. With this technology, the scanner can adjust radiation exposure for different parts of the body during a scan. Moving over the breasts, it will shift focus and reduce exposure, Huda says. It will also vary exposure according to body parts’ mass. “It’s the most dose-saving method, and it doesn’t subtract from diagnostic performance,” Huda says.
Huda is planning a study to show how much automated exposure controls can reduce radiation to the breasts, particularly in younger females. “It might be a 5% to 50% reduction,” he says. “My guesstimate is 35% to 50%.”
Whether or not radiology departments can rely automatically on dose-limiting software was called into question when a report in the New York Times7 blamed overradiation incidents at two sites on dose-limiting software that may have contributed to overexposure. Unlike the breast-dose–saving software referred to by Huda, the software program in question is related to a noise index and is proprietary.
J. Anthony Seibert, PhD, president-elect of the Association of Physicists in Medicine and professor of diagnostic imaging physics at the University of California–Davis, speculates that the overexposures could have been the result of an unreasonably low setting of the noise index that caused the milliamperage to max out at eight times the optimal dose. The result is that now, everyone has a better understanding of the significance of the volume CT dose index.
“The technology is outstripping the trainer’s ability to train and the learner’s ability to learn,” Seibert notes. “We, collectively—not just the manufacturers, but the receivers of the information—do not do enough or pay enough attention, in terms of commissioning a piece of equipment, the impact of what these values mean, the potential hazardous use of the equipment, and untoward outcomes that can occur in the use of the equipment.”
Mayo-Smith advises ongoing vigilance. “It is very important that radiology departments create a team approach to reviewing CT protocols for dose parameters, to make sure protocols are created not only to optimize image quality, but to minimize dose,” he notes. “This is an ongoing process, particularly as new indications for CT examinations are created and new protocols are developed.” He recommends that the team include a radiologist, a physicist, and a lead technologist.
Huda is not a fan of attempting to collect cumulative dose information on patients. If radiologists are following ALARA and risk–benefit judgments, he asks what the point would be. “For the cumulative effect of indicated exams, I don’t see any value in adding up the radiation,” he says.
Of course, the fact that a patient has had multiple CT exams might figure into the risk–benefit decision on ensuing scans. That’s one reason that Huda calls for the exposure summary on every exam to be dictated from the PACS when a radiologist completes a report, along with a notation that the exposure level produced (or failed to produce) a readable image. That way, instances of using too much or too little exposure to yield a readable exam can be tracked as well. “I’m in the process of doing that at my institution,” Huda says.Dose TrackingGeorge Shih, MD, is assistant professor of radiology at Weill Cornell Medical College, New York, New York. He is also a computer enthusiast. Working with a team of medical physicists at Columbia University, Shih has come up with a system for tracking CT radiation exposure for inpatients that he believes can be extrapolated to radiology in general. Shih calls his system Valkyrie.
Valkyrie, Shih says, has extracted CT radiation exposure data, so far, with 100% accuracy. On newer machines, it takes the data directly from the scanner, but on older machines, where there are no scanner data, it relies on “text embedded in the images—CT screenshots,” Shih says. He adds that his team was able to use connected components to extract the exposures from the screenshots.
Valkyrie is still in a nascent stage, Shih says. It’s not patented, and it’s only available for Weill Cornell inpatients, but for them, it works. It automatically records—on what is now a stand-alone server—the exam exposures (based on manufacturers’ estimates using phantoms), and it adjusts those figures based on the patient’s actual size and weight. If Valkyrie sees excessive exposures, it automatically contacts radiologists by email so that the problem can be corrected at once, Shih says.
“Immediately, there are people alerted,” Shih says. He admits this hasn’t happened yet in a real setting because only three scanners are connected to the system, and it’s new. Any overexposure not caught before the first exam, however, should be caught thereafter, preventing more excessive exposures. “We’ve had nothing adverse yet, but we’re ready if something happens,” Shih says.
Another advantage of Valkyrie is that it could be used retrospectively to extract exposure data from any PACS archive. That might lead to a better understanding of health-care–related radiation exposure, Shih says. For now, though, Shih is satisfied to have a new quality-control tool, which might or might not have a commercial or industry-wide application.Dose RegulationAt the March meetings called by the FDA, the major powers in the imaging industry—scanner manufacturers, medical societies, and government agencies—all lined up behind the principle of reducing radiation exposure, despite a lack of proof that widespread cancer increases will result from imaging being done as it is now. Better safe than sorry was a major theme.
Today, however, there is no regulatory body charged with making certain that radiation exposure limits are applied or enforced. Only four states require medical physicists to be licensed, and many states have yet to license radiologic technologists. Who will take the lead in further regulation, if there is any, is unclear. Some call for the federal government to step in; some want the states to take charge.Alberto Gutierrez, PhD, is director of the Office of In Vitro Diagnostics at the FDA’s Center for Devices and Radiological Health. Trained as a chemist, Gutierrez is now charged with overseeing imaging-device radiation safety for the FDA. The FDA’s essential role, he says, is clearing scanners and other devices for safe use.
“We can require the manufacturers to put in safeguards, if we believe they’re necessary for a safe and effective manner of operation,” he says. “We can make sure manufacturers put alerts on the machines and keep records. We can require checkers on dosage and alarms if procedures go beyond a certain amount of radiation. The manufacturers have agreed on putting in appropriate alerts.”
What the FDA can’t do, Gutierrez says, is monitor the practice of medicine in hospitals and clinics where imaging techniques are put into play. “We can do things like clear safeguards with CMS,” to make sure that the machines are used correctly, he says. “We do play a role in that area. We partner with CMS to keep up quality-assurance practices for imaging facilities and hospitals.”
Now, he adds, the FDA is meeting with industry and medical-society representatives to “talk about how to establish a national dose registry and diagnostic reference levels,” he says. Gutierrez adds, “There’s a good chance the FDA will work on guidance documents and continue careful monitoring of all the manufacturers on whether we are seeing more radiation overexposures, and if we are, we will continue to bring those to the attention of the manufacturers and the medical community to determine what needs to be done.”
When it comes to regulation, Gutierrez takes a softer stance. “From the exposure events that we have seen, we don’t believe that this is an area in which we would need to change regulations, or where the manufacturers did something wrong, per se,” he says.
The FDA is unlikely to seek a regulatory role for itself; Gutierrez says, “National regulation is not our purview.” Nonetheless, the days when imaging facilities and hospitals could proceed as usual, while patients’ exposure to radiation grew in company with exam volumes and the number of CT detectors, appear to be gone.
The California legislature is proving the point. The California Senate recently passed SB 1237, which would, beginning in 2012, require—if technologically feasible—health facilities and clinics to record the dose of radiation received by a patient during a CT scan and input that dose as part of the patient’s medical record. The bill is now being considered by the California Assembly. Compliance for rural providers would be delayed until 2013. Accreditation of high-end imaging providers would also be mandated. The California Department of Public Health would have regulatory control. George Wiley is a contributing writer for Radiology Business Journal.