Medical Imaging Needs a New Image

by Miriam Goodman

Do you know how much radiation exposure that you will receive from that recommended CT scan and the health risks involved? If you don’t, you’re not alone; and there’s a very good chance that neither does your doctor.

“In the same exam you can be getting ten times as much as somebody else,” noted David Brenner, MD, of Columbia University Medical Center. The dam is finally breaking within the medical community, which is waking up to the radiation risks from X-ray imaging, particularly CT scans and nuclear medicine. A plethora of recent studies and editorials in prestigious journals have raised the alarm about an expected increase in future cancers by the tens of thousands annually, due to the enormous explosion in the use of computed tomography (CT). From the early days of X-rays, when physicians, and even shoe stores, were using this seemingly amazing technology for all kinds of benign conditions, the medical profession has given scant attention to the potential risks. Dr. Rita Redberg, editor of Archives of Internal Medicine, warned that, if complacent, “we risk creating a public health time bomb.” One of the studies estimated there would be 29,000 cancers from CT performed in 2007, half of them fatal, mostly from scans of the abdomen and pelvis, chest, and head, as well as chest angiography.

CT delivers a much higher radiation dose than conventional X-rays and, along with nuclear medicine, comprises 75% of medical radiation exposure. In 2007, there were 69 million CT scans done in the US, about 4 to 7 million of these performed on children. Sixteen million nuclear medicine scans are now done annually. A study by Dr. Fred A. Mettler Jr., of the University of New Mexico, and others found that in one CT exam, 30% of patients get 3 scans, 7% get 5 scans, 4% get 9 scans, and trauma patients initially get 3 scans. Yet it is estimated that of about 50,000 radiologic technologists who perform CT, only 23,000 are certified in CT. The radiation dose from a CT scan of the abdomen, for example, is equivalent to that from 400 conventional chest X-rays. A chest CT delivers an organ dose to the breast equal to about 15 sets of mammograms. Inasmuch as medical radiation is a scientifically established cause of breast cancer, minimizing such exposure to breast tissue is critical. The dose range to body organs from CT is the same as that which has been found to cause cancer mortality in the A-bomb Survivor Study.

As reported in the New England Journal of Medicine, 8l.8% of the total radiation dose to the US population was delivered in outpatient settings, most often in physicians’ offices. They noted one study of health-care providers using CT, in which 50% of radiologists and only 9% of emergency department physicians reported even being aware that CT was associated with an increased risk of cancer. Award-winning scientist John W. Gofman, MD, PhD, raised concerns about radiation overdosing from medical X-rays in his 1995–1996 Preventing Breast Cancer: the Story of a Major, Proven, Preventable Cause of This Disease. His 1999 medical monograph Radiation from Medical Procedures in the Pathogenesis of Cancer and Ischemic Heart Disease, assembles powerful evidence that medical radiation is a necessary contributor (but not the only necessary one) in causing over 50% of the death rates from cancer and coronary heart disease during the 20th century. The term medical radiation here refers primarily to X-rays, which include CT scans and fluoroscopy, as well as conventional X-rays. Current estimates of cancers caused by medical radiologic imaging are lower than those of Gofman because the former are primarily based on the A-bomb study, a study of persons exposed to radiation from a non-X-ray source. In light of the fact that since the advent of X-ray technology, radiation doses have not been measured and recorded, the absence of data on cumulative lifetime X-ray exposures of the individuals in the A-bomb study groups obscures the magnitude of the X-ray risks. Further, experimental evidence in radiobiology that X-rays are 2 to 4 times as mutagenic, at equal unit doses, as the high-energy Hiroshima-Nagasaki gamma rays on which most radiation risk estimates are based, makes current risk estimates underestimates.

In the past decade, warnings began to appear in journals about pediatric CT. The National Cancer Institute published Radiation Risks and Pediatric Computed Tomography (CT): A Guide for Health Care Providers. The greater sensitivity of the young to radiation makes this an important wake-up call. Further, compared with adults, children have many more years of life ahead, time during which a radiation-induced tumor can grow, possibly potentiated by other environmental exposures. They warn that, contrary to frequent practice, exposure settings should be customized for children. Additionally, they suggest that alternatives to radiologic procedures be considered.

With regard to the conventional wisdom in science that the radiation risk of cancer decreases as people age, a new study in the Journal of the National Cancer Institute finds that exposure risks for some tumor types may increase in middle age, due to promotion of cancer in preexisting, premalignant cells, rather than initiation of premalignant cells via gene mutation.

The nascent awareness about radiation risks from medical imaging moved fast-forward after news reports early last year about horrendous accidents and errors in the use of high-dose radiation cancer therapy precipitated a congressional subcommittee hearing. Concerned about possible rejection of the benefits of medical radiation by the public, as well as unnecessary harm from radiation exposure, representatives of all sectors of the radiation community in medicine – physicians, technologists, medical physicists, and equipment manufacturers, as well as cancer patients, testified at the hearing to the need for oversight and regulation of both therapeutic and diagnostic medical radiation practice. Noncancer patients, who make up the majority of the patient population – those who undergo screening, diagnostic, or interventional radiologic imaging during placement of catheters and during surgery – were not represented. The committee members heard a litany of complaints about unlicensed personnel, lack of accreditation, inconsistent standards among the states, absence of data collection on radiation doses, and large disparities in dose – all of which reflect similar concerns reported periodically in past decades. One such early account of outrageous X-ray practices appeared in 1985 in the Wall Street Journal.

No mention was made at the hearing of optimizing shielding of body organs adjacent to the field of diagnostic interest in order to reduce exposure. Also missing from the discussion and from proposed legislation was dental imaging. Conventional dental X-rays, though considered low in dosage, often give higher radiation doses because of outmoded X-ray film. They are performed frequently, often routinely, in each dental patient’s lifetime, starting in childhood and use of which for many years neglected to shield parts of the body from scatter radiation, including the thyroid gland and the eyes. Very problematic, if not alarming, is the growing use of CT scans in dental offices. Promotion and routine use of these so-called cone-beam CT scanners have raised serious concerns with regard to benefit vs. risk. New research from England demonstrated that thyroid cancer risk increases as the number of dental X-rays taken grows, but add the caveat that historical dental X-ray records were not available. Dental X-rays have also been linked to brain and salivary gland tumors, according to the lead investigator.

Several witnesses at the hearing called for passage of the CARE bill (HR 3652; the Consistency, Accuracy, Responsibility and Excellence in Medical Imaging and Radiation Therapy Act), which has been introduced in every congress since 2000. A Senate Care Act (S-3737) has recently been introduced. Recurring themes at the hearing were the need to minimize radiation doses, use this technology only when necessary, and enter radiation doses electronically into the patient’s medical record. Dr. Steven Amis, professor and chair of radiology at Albert Einstein College of Medicine, as well as others, called for a CT radiation dose registry. Dr. Rebecca Smith-Bindman, a professor at the University of California-San Francisco, testified, “… in diagnostic medical imaging we have very little data about what is currently going on about actual doses. Recording and tracking dose information would help educate patients and providers about radiation exposure and would lead to activities to minimize dose. Guidelines are needed about what is an allowable dose. Manufacturers of equipment can play a role in this.”

Following closely on the congressional hearing, the President’s Cancer Panel report weighed in on medical radiation and cancer and the need for reduction in exposure. At their conference on radiation, as part of a series on the environment and cancer in 2008–2009, they heard that “many primary care physicians and other referring medical professionals are unaware of the magnitude of radiation exposure or the potential cancer risk.” Among the participants, David Brenner was of the opinion that “a third of all CT scans practically could be replaced by other approaches or don’t have to be performed at all. But it’s going to be really hard to target this one-third because there are so many pressures on physicians to do CT scans.” In this regard, one cannot ignore the high profitability of medical imaging and the fact that investment in expensive equipment is important motivation for greater utilization.

Early on in the effort to increase awareness about radiation overdosing in medical imaging, the Committee for Nuclear Responsibility (founded by Dr. Gofman) issued a policy statement emphasizing that medical and dental X-ray patients have the right to know that their radiation doses are measured, not calculated or estimated, and to have a reliable dose record. This in many instances could be easily and inexpensively implemented, as it is with nuclear workers, by use of a thermoluminescent dosimeter (TLD) on the patient during an imaging procedure. Available from CNR is its valuable Patients’ Guide, When X-Rays Are Proposed” (www.x-raysandhealth.org), because a truly informed patient asking the right questions before undergoing CT, fluoroscopy, or conventional X-rays can substantially reduce his or her radiation exposure.

Redberg urged her journal readers to make a multifaceted effort to avoid excess cancers, including using the lowest-dose technique, improving radiation protocols, eliminating the significant number of inappropriate scans, and fully informing patients about radiation risks. The latter instruction, of course, is totally dependent on a risk-educated physician. A number of institutional initiatives in the past year or two have been announced, including the Food and Drug Administration’s focus on reducing unnecessary radiation exposure from the three highest-dose medical imaging procedures – CT, nuclear medicine, and fluoroscopy. The latter uses continuous X-ray beams that produce images to view in real time during many common procedures such as GI, cardiac, and urinary-related exams, among many others. It exposes sections of the body to X-rays at varying high-dose rates per minute. Authoritative sources have voiced the criticism that many users of fluoroscopy equipment do not understand its proper use, or the principles of radiation protection. In its advocacy of adoption of two of those principles – appropriate justification of the radiation procedure and optimization of the radiation dose used – and under its regulatory oversight of medical imaging devices, the FDA plans to collaborate with other federal agencies and health professional groups to incorporate key quality assurance practices into mandatory accreditation for imaging facilities and hospitals. In addition, it intends to require manufacturers of devices to incorporate safeguards into machine design and to provide appropriate training to support safe use by practitioners. An important aim of the initiative is to increase patient awareness of his/her own exposure, including developing a patient medical imaging history card.

In tandem with the NCI’s guide on pediatric imaging is another effort to lower radiation doses to children, too many of whom are unnecessarily being exposed to an adult-level radiation dose. The “Image Gently” campaign of the Alliance for Radiation Safety in Pediatric Imaging, a coalition of health-care organizations, has produced educational materials for health-care providers and parents. Their child medical imaging record form includes type of exam, but no requirement for the actual radiation dose received. Among other initiatives in response to radiation exposure concerns are programs of the American College of Cardiology and American College of Radiology, which they say should be mandated, not voluntary.

The current turbulence within the health-care community with regard to use of radiation is based on the recognition that there is no safe dose of radiation, that risk is proportional to dose down to zero dose. But that knowledge has been concerned solely with the risk of cancer, with no apparent awareness of two additional major risks. One is the evidence of low-dose medical radiation as a contributing cause of heart disease in Gofman’s work. This link has been taking on currency in other research, such as the A-bomb study and a British study of nuclear power plant workers, but has been called controversial. However, it needs to be given serious attention. Unmentioned, too, is genetic damage from irradiation of the reproductive organs, potentially leading to any of a multiplicity of health effects in future generations. In light of the very commonly performed abdomen/pelvic CT, how many individuals have been so exposed?

Though the testimony given at the congressional hearing was quite clear and fairly comprehensive in detailing the need for changes in medical use of radiation, committee chairman Frank Pallone ended the hearing noncommittal about future legislation, concluding that he had more questions than answers and might call for another hearing. The various initiatives and strategies for dose reduction that are in place are an important and welcome development. But voluntary implementation will not be optimal if the risks continue to be characterized as “small” and will not have the force of a federal legislative mandate. Toward that end, what is crucially needed is organized advocacy by proactive patients informed about radiation risks.

Medical imaging is an essential, often life-saving, and life-enhancing component of health care. But lack of knowledge of, and even resistance to, the scientific data on radiation and human health by medical practitioners, as well as the “essentially unregulated” use of radiation in medicine, as Mettler put it, have resulted in the excesses that tarnish its image. Public and professional ignorance of the potential cancer, hereditary, and cardiovascular risks of cumulative exposure to medical radiation has prevented this issue from entering patient–doctor communication, which otherwise could often offer safer alternatives in care. If patients are to have the radiation protection that they deserve, they must play an important role. When the public, and even some physicians, begin to wonder if the risks of radiologic imaging supersede the benefits, it’s time for the medical community to do everything necessary to “first do no harm.

Miriam Goodman

midislandradiationalert@yahoo.com