Technological advances in medicine have given physicians the tools to diagnose and treat diseases much more quickly and accurately than they did a generation ago. Diagnostic imaging techniques are an area in which improved and more available technology have tremendously benefited patients. However, as the use of diagnostic imaging technologies has increased, we have also come to appreciate the risks associated with these interventions. Foremost among these risks is the potential for harm related to excess exposure to ionizing radiation.
Several commonly used diagnostic imaging techniques include computed tomographic (CT) scans, fluoroscopy CT, and nuclear medicine scans. CT scans send X-rays through the body area being studied, with each scan rotation providing a slice of an organ or body area to form a complete picture of the area. Fluoroscopy uses a steady beam of X-rays to track movement of organs within the body, to guide a needle for biopsy, or to guide other instruments in real time during invasive procedures such as cardiac catheterization. Nuclear medicine scans use a special type of camera that images gamma-radiation–emitting radioisotopes in organs or tissues that have absorbed a radioactive tracer that is injected in a vein in the patient's arm. The camera image shows the activity and function of the tissues or organs being studied. Many patients are exposed to ionizing radiation during these scans. In addition, the increasing use of imaging—CT scans in particular—has exposed many patients to large doses of radiation. Since ionizing radiation has the potential to cause cancer by damaging a person's DNA, there is considerable concern (supported by a growing body of literature) that radiation exposure from medical imaging may put patients at risk for developing cancer. Cancer risk from radiation exposure is a future statistical risk that is not known at the time of exposure. There are also risks of adverse events such as radiation burns (more common in radiotherapy), which are evident shortly after exposure.
Approximately 40% of patients diagnosed with cancer receive radiation therapy at some point in their treatment. As the use of radiotherapy for certain types of cancer has grown, providers and researchers have raised concerns about the safety of radiation exposure. This Patient Safety Primer will discuss the safety issues associated with the use of radiation, both for diagnosis and therapy.
Radiation Risks Associated With Diagnostic Imaging
Population-based studies show that the use of diagnostic imaging has exploded over the past two decades, with one population-based study showing that the number of CT scans per 1000 adult patients nearly tripled between 1996 and 2010. More than 85 million CT scans were performed in the United States in 2011. This has led to a dramatic increase in ionizing radiation exposure to individual patients and the general population. While other imaging techniques also use radiation, CT is estimated to account for half of all medical radiation exposure, partly because more CT scans are being performed, but also because the radiation dose per scan has increased. Newer multidetector CT scanners produce much higher resolution images, which can aid in diagnosis, but also expose patients to 30%–50% more radiation than older scanners. Since ionizing radiation is a known carcinogen, it is likely that some patients who undergo CT scans with high doses of radiation, or patients who undergo many CT scans, will develop cancer as a result of the scans. Although work in this area remains controversial, one study estimated that as many as 1 in 80 young women who undergo a multiphase CT scan (repeated scanning before and after injection of a contrast dye) of the abdomen and pelvis will develop cancer later in life as a result. The expansion of interventional radiology and interventional cardiology has also increased the use of fluoroscopy, which involves significant potential radiation exposure for both patients and staff.
Variability in radiation dose also plays a role in the increasing radiation exposure attributable to medical imaging. Radiation dose varies widely for different types of examinations and is operator- and facility-dependent as well. One study showed that even for the same type of CT examination, the radiation doses varied as much as 13-fold among different institutions and different technologists within the same institution. This variation often occurs due to failure to adjust radiation dosage based on body size. Many experts believe that adequate images can be obtained with doses at the lower end of the ranges, as seen in such studies. To the extent that this is true, observed doses at the higher end of the ranges contribute to excessive radiation exposure even when the CT scan is clinically indicated. Use of higher-than-recommended radiation dosages can also increase radiation exposure to staff, and failure to appropriately narrow the radiation beam or shield body parts that do not need to be imaged can result in unnecessary radiation exposure even when a scan is indicated.
Risks Associated With Radiotherapy
The field of radiation oncology is technologically sophisticated, and radiotherapy requires close collaboration among physicians, technologists, and medical physicists. Like any procedure that requires close coordination with a multidisciplinary team, errors that occur with radiotherapy usually arise from multiple causes and are attributable to underlying systems issues, such as communication problems. A review of 30 years of published data on safety in radiotherapy found that the overall incidence of errors was relatively low, estimated at 1500 per 1 million treatment courses. However, this number is likely an underestimate, since there is currently no mandatory reporting standard for injuries due to radiotherapy.
Errors that harm patients generally involve overexposure to radiation, which can cause direct toxicity; cases of wrong-patient and wrong-site errors have also been reported. Root cause analyses of harmful radiotherapy errors often cite poor communication among providers, particularly at the treatment planning stage, as a common source of error. These issues may be exacerbated by the use of different software programs and varying types of radiotherapy equipment. A 2010 news investigation found that many cases in which patients experienced serious harm were due to wrong dosing or incorrect configuration of equipment, often attributable to inadequate training with new equipment, poor interoperability of systems, and other human factors engineering issues. Standards for licensure and certification of technologists and treatment facilities also vary among states.
Improving Radiation Safety
The Joint Commission issued a Sentinel Event Alert in 2011 that highlighted the risks of diagnostic imaging and outlined specific strategies organizations should take to minimize the risks of radiation. The alert emphasized the importance of educating physicians on appropriate test utilization and standardizing equipment and radiation dosage as two key interventions. These guidelines call for ordering physicians, radiologists, and technologists to establish a system that prioritizes using the right test and the right dose of radiation to achieve the desired diagnostic objective. Since implementing processes for monitoring the safety of imaging equipment, establishing standards for test ordering, and standardizing radiation dosages will require considerable leadership support, The Joint Commission also emphasized the role of an overall culture of safety in addressing radiation safety specifically.
It is worth emphasizing that eliminating unnecessary imaging, or replacing CT scans with safer studies like ultrasounds or magnetic resonance imaging, is as important for reducing the risks from unnecessary radiation exposure as lowering the dose of radiation per imaging test. Information technology can supplement clinician education in this area. For example, a systematic review of studies showed that use of computerized provider order entry (which typically provides dosage and other guidance to doctors when they enter orders in the system) increases adherence to radiology test ordering guidelines and thereby decreases overall radiology use. Many professional societies and other organizations are now conducting large-scale campaigns to reduce unnecessary radiologic imaging and to improve safety by standardizing radiation dosing. Prominent national examples include the Image Wisely campaign and the pediatric initiative, Image Gently. The Joint Commission also has promoted a public awareness campaign on medical imaging safety.
Improving the safety of radiation therapy relies in part on similar principles, including enhancing safety culture and standardizing training and equipment. Given what is known about factors that contribute to radiotherapy errors, it seems plausible that teamwork training and attention to human factors engineering principles may augment safety, but formal studies of these approaches in radiation oncology are lacking.
Like all issues that have been the subject of Sentinel Event Alerts, radiation safety will be monitored by The Joint Commission as part of its accreditation site visits. Several regulatory steps have also been taken to improve the safety of diagnostic imaging. For example, since many imaging tests are performed in outpatients, since 2012, the Centers for Medicare and Medicaid Services has required the accreditation of freestanding facilities that provide advanced imaging services. The state of California now requires documentation and disclosure of the radiation dose of all CT examinations and requires that all radiation dose errors be formally reported and disclosed to patients.