EHRs Help Track Cumulative Radiation Dose

Despite growing concern over CT-related radiation exposure, measuring risks of cumulative exposure from CT imaging in a standardized or formal way is not part of routine practice for most ordering physicians—something that could change with more widespread use of electronic health records (EHRs).

Richard T. Griffey, M.D., M.P.H. Washington University School of Medicine

Aaron D. Sodickson, M.D., Ph.D. Brigham and Women’s Hospital and Harvard Medical School

Diego B. Nunez Jr., M.D., M.P.H. Hospital of Saint Raphael

The need for a risk stratification method is becoming increasingly important in light of new research that shows that frequent or recurring CT use correlates with a heightened risk of developing cancer from cumulative radiation exposure, according to Richard T. Griffey, M.D., M.P.H., an assistant professor in the division of emergency medicine at Barnes-Jewish Hospital at Washington University School of Medicine in St. Louis.

"The number of CT scans is skyrocketing and the risk side of the risk-benefit equation needs more attention," said Dr. Griffey. "This is certainly true in the emergency department, where physicians often don't have the time or ability to scroll back and retrieve this element of a patient's history. Ideally, physicians could be informed at the point of ordering a CT whether a patient is at heightened risk of developing cancer from cumulative radiation exposure."

Dr. Griffey and Aaron D. Sodickson, M.D., Ph.D., assistant director of emergency radiology at Brigham and Women's Hospital (BWH) and Harvard Medical School in Boston, co-authored a study in the April 2009 issue of the American Journal of Roentgenology showing that a small cohort of emergency patients undergoing CT accrued large cumulative radiation doses from frequent or recurring CT.

In the April 2009 issue of Radiology, a larger study by Dr. Sodickson and collaborators at the BWH Center for Evidence Based Imaging (CEBI) used automated methods to study cumulative CT exposures and estimated risks for more than 31,000 patients undergoing CT at BWH. They estimated that historical CT exposures are expected to produce 0.7 percent of the total expected baseline cancer incidence and 1 percent of the total cancer mortality. In particular, frequently scanned patients accrue large cumulative radiation doses and substantially increased levels of risk, the study showed.

Radiation dose is on the agenda for the RSNA 2009 Emergency Series: Managing Your Emergency.

Co-moderator Diego B. Nunez Jr., M.D., M.P.H., chair of the Department of Radiology at the Hospital of Saint Raphael in New Haven, Conn., and an associate editor of Radiology, said advancements in CT technology—combined with media attention and the sheer volume of multi-trauma and other CT cases handled by EDs each day—have put radiation exposure at the forefront of issues facing emergency radiologists.

"In the past 15 years, we've gone from a single detector to a 64-channel multidetector row, which has increased our ability to scan faster and cover greater portions of the body," said Dr. Nunez. "While this capability has increased our reliance on CT, it has also created concerns about radiation exposure and overutilization, especially in the emergency department."

Study Gauges Radiation Risk

Drs. Griffey and Sodickson identified all patients over a one-year period, who made at least three visits to the BWH ED, in which they underwent a CT scan of the neck, chest, abdomen or pelvis. For those 130 patients, Drs. Griffey and Sodickson then identified all diagnostic CT studies performed at any site in the hospital over the previous 7.7-year period. Of the 1,744 CT studies captured, 55 percent were performed in the ED.

To estimate cumulative radiation dose, each patient's cumulative CT effective dose was converted to lifetime attributable risk using the standardized Biologic Effects of Ionizing Radiation (BEIR VII) dose-to-risk conversion factor of one cancer per 1,000 patients receiving a 10-mSv effective dose. Results showed that over half of the group had accrued estimated radiation-induced cancer risks above baseline of greater than 1 in 110, up to a maximum of 1 in 17.

Technology Can Address Issue

Overcoming the technological hurdles to routinely perform individualized radiation risk assessment could take years or even decades. But healthcare systems can begin by adopting the EHRs needed to track a patient's examination and radiation dose history within their own facility or network.

At BWH, the informatics team at CEBI is using EHRs to develop an automated decision support tool that will provide real-time point-of-care radiation risk assessments to ordering providers.

"Ideally, physician orders for CT would first query a universal database indicating whether the patient is in a high-risk category for radiation exposure," said Dr. Griffey. "If so, the computer decision support tool could suggest an alternative modality such as ultrasound or MR imaging, or it might facilitate real-time consultation with a radiologist about the best imaging strategy. Right now this is not something that is often done or even thought about in any systematic fashion."

In fact, a recent study presented at the American Roentgen Ray Society annual meeting found that the majority of ordering physicians have limited knowledge of CT-related radiation exposure and its associated risks.

In an anonymous, Internet-based survey of ordering physicians at a regional tertiary care teaching hospital, lead author Jeremy McBride, M.D., from the Carilion Clinic in Roanoke, Va., and colleagues, asked respondents to rate the influence of certain factors when ordering CT scans. While 100 percent of respondents rated the ability of CT to rule in/out a diagnosis as influential, concern over radiation exposure was an influential factor for 22 percent and cumulative radiation exposure for 19 percent. When asked to identify the equivalent radiation exposure a CT scan represents in plain radiographs, 64 percent of respondents underestimated the dose, according to the survey.

That awareness level will increase among physicians as the spotlight on radiation risks begins to impact routine medical practice, said Dr. Griffey.

Dr. Nunez agreed that physicians who frequently turn to CT as their only imaging option will need to be educated on attendant radiation risks as well as the potential for other imaging modalities.

"It becomes more critical to use clinical predictors to determine the likelihood of a patient having a given disease, and not always rely on CT as the first option," he said. "We need to educate the ED physicians on potential issues with radiation and the development of appropriate imaging methods."