During the past few years, the risks of overexposure to radiation from medical imaging tests have become a hot topic of conversation among healthcare providers. Cumulative radiation dosage tracking offers a way to protect patients.
According to a 2009 report by the National Council on Radiation Protection & Measurements (NCRP), Americans’ exposure to ionizing radiation has nearly doubled during the past 20 years. The increase is largely due to exposure from medical imaging, including fluoroscopy, nuclear medicine procedures and computed tomography (CT). In most cases, the benefits of these tests outweigh the risk of radiation exposure.
But a 2010 report published in Radiology estimates that as much as 50 percent of these exams may not be medically necessary, which not only contributes to increasing healthcare costs but also exposes patients to unwarranted risk. How much risk? In a 2009 study published in the Archives of Internal Medicine, researchers estimated that the 72 million CT scans performed in 2007 alone would result in 29,000 excess cancers, which may cause as many as 15,000 deaths annually over the next 20–30 years.
Government agencies as well as scientific and medical societies have taken steps to curb overutilization of imaging exams, work with imaging device manufacturers on automated safety features and develop practice guidelines that make radiation safety a priority. Until recently, radiation exposure data to support the creation of guidelines was collected only on entire populations. Now, the focus has shifted to tracking cumulative dosages for individual patients.
In 2009, the risks of radiation overexposure attracted national attention when Cedars-Sinai Medical Center in Los Angeles disclosed that more than 200 stroke patients had accidentally been exposed to extremely high levels of radiation during CT brain scans. After many patients reported losing hair — a side effect not normally associated with CT — the hospital discovered that a CT machine had been delivering as much as eight times the normal level of radiation for the previous 18 months. While the patients’ hair loss was temporary, the long-term health effects of the overexposure are unknown.
This mishap prompted the FDA to issue an alert instructing hospitals to review their protocols and CT operators to check dose indices on the control panel before and after scanning. In 2010, the FDA launched the Initiative to Reduce Unnecessary Radiation Exposure from Medical Imaging to promote the appropriate use of medical imaging; educate radiology technicians, physicians and the public about the risks of radiation exposure; and improve how radiation dosages are measured and recorded.
Getting on Track
In the wake of the Cedars-Sinai incident, lawmakers also responded to public concerns about radiation safety. In 2010, California enacted a law that requires healthcare facilities to record radiation doses and report any errors to patients, their physicians and state health agencies. Perhaps anticipating that additional state laws or federal regulation may soon follow, some healthcare providers have begun tracking cumulative radiation dose voluntarily. For example, in 2012, Intermountain Healthcare in Utah began tracking total radiation exposure for all patients — though only from tests and treatments received at Intermountain facilities — and including the data in their electronic health records (EHRs).
Documenting radiation exposure within one facility or health system is an important first step, but patients may receive radiation at a number of unrelated facilities in the course of treatment. How to integrate dose tracking from one facility to another remains an unsolved challenge. Until nationally standardized and integrated EHRs allow facilities to share data easily, the American College of Radiology (ACR) offers a low-tech solution — a downloadable Image Record Card that patients can use to record radiation dose data from all facilities visited. The International Atomic Energy Agency is also working on an electronic version called Smart Card, which is still in the prototype stage.
How Much Is Too Much?
Now that healthcare providers have the ability to document radiation dosages, the question remains: How should clinicians interpret the data?
The current method of estimating the health effects of radiation is the linear no-threshold model, which assumes that risk is directly proportional to cumulative dose, meaning many low doses are as dangerous as one high dose.
The model is not universally accepted, however, with some researchers claiming the body can repair damage from low levels of radiation. Clinicians may also be unsure how to factor the model into day-to-day testing decisions. In a 2013 survey of radiologists by Massachusetts General Hospital, 92 percent reported taking patient exposure history into account, and 61 percent believed in the linear no-threshold model. Yet 64 percent made decisions that were inconsistent with this belief, and just 4 percent demonstrated a solid understanding of the model’s significance.
Despite disagreement or confusion about radiation risks, most healthcare providers agree that exposure should be kept to a minimum until acceptable dosage thresholds are established. Dosage tracking offers a means to accomplish that end.
In 2011 the ACR launched the Dose Index Registry, which allows facilities to compare their CT dose rates with those of other facilities across the country. By February 2013, the ACR had logged more than 5 million CT scans, bringing the registry closer to its goal of collecting enough data to establish national benchmarks for dose indices.
Education and Reassurance
In the meantime, the ACR has issued Appropriateness Criteria, a set of guidelines to help providers make the best use of radiologic tests and treatments for a variety of conditions. The criteria are available on the ACR website, www.acr.org. The ACR is also a major sponsor of Image Wisely (www.imagewisely.org), a task force that promotes radiation safety in adult medical imaging, and Image Gently (www.pedrad.org), its pediatric counterpart. Both organizations offer materials aimed at educating the medical community, as well as helping physicians answer patient questions about radiation risks and the benefits of radiologic tests and procedures.