Counter-Point: Are We Really Ordering Too Many CT Scans?

E ditorial Counter-Point: Are We Really Ordering Too Many CT Scans? David T. Schwartz, MD Associate Professor of Emergency Medicine, New York University School of Medicine Supervising Section Editor: Seric S. Cusick, MD Submission history: Submitted February 19, 2008; Revision Received March 23, 2008; Accepted April 2, 2008. Reprints available through open access at www.westjem.org [WestJEM. 2008;9:120-122.] In a recent review published in the New England Journal of Medicine, DJ Brenner and EJ Hall, professors of Radiation Biology at Columbia University, analyzed the current trend to increased use of computed tomography (CT) scanning, the attendant radiation exposure, and the long-term potential for induction of fatal malignancies in the population. 1 This article was widely discussed in the popular press and on television news with headlines such as “Unnecessary CT scans exposing patients to excessive radiation: cancer cases could spike as a result,” “Doctors may risk overuse of CT scans,” and “The doctor says get a CT scan. Should you?” 2-6 The original journal article and subsequent news coverage stated that one-third of CT scans are medically unnecessary, needlessly exposing millions of patients to high doses of radiation. However, the “evidence” on which this statement was based was insubstantial. In an ad hoc survey conducted during a panel discussion at a meeting of pediatric radiologists, a speaker mentioned that he felt 10% of CT scans were not medically necessary. 7 He then queried the audience, which responded that up to 30% were unnecessary. Aside from the fact that this was merely a casual inquiry, these are not the people making clinical decisions about patient care. Emergency physicians (EPs) have, to some extent, been singled out with regard to this issue since we are responsible for ordering many CT studies. Dr. Brenner is quoted in USA Today as stating: “Virtually anyone who presents in the emergency room with pain in the belly or a chronic headache will automatically get a CT scan. Is that justified?” Dr. Fred Mettler, chief of Radiology at the New Mexico Veterans Administration Hospital, was quoted by MSNBC: “The pressure is greatest for ER doctors who ‘are in a bind ... they have all these patients stacked up’ and need to make quick decisions.” Again, it was not clinicians who made these statements, and they do not reflect the practice of high-quality emergency care. EPs were also cited for being unaware of the magnitude of the radiation dose associated with CT scanning. In one survey, 91% of EPs did not believe that CT scans were associated with an increased risk of fatal cancer. 8 Clearly this misperception should be remedied, but its impact on clinical care is less certain. The Western Journal of Emergency Medicine In actuality, there is abundant evidence demonstrating the considerable benefit of CT in managing emergency department (ED) patients, substantially outweighing its risks. In fact, in some circumstances (e.g., patients with acute headache) we may not perform CT scans frequently enough. Nonetheless, the issue of radiation exposure with CT scanning is an important one and needs to be considered in clinical practice. Increasing CT Usage and Radiation Exposure In their review, Drs. Brenner and Hall 1 describe the marked increased in the use of CT scanning, from three million scans in the U.S. in 1980, to 20 million in 1995, to over 60 million in 2005. Although the risk for an individual is small, in a few decades up to 2% of all cancers may be due to radiation exposure from CT scans, an increase from the current estimated rate of 0.4%. In addition, CT use is projected to increase even more in the future due to screening of asymptomatic patients, such as chest CT for lung cancer in smokers, virtual colonoscopy and cardiac/coronary artery scans. However, before any screening program is instituted, its benefit over the risks of radiation must clearly be established. CT, particularly multidetector helical CT, is exceedingly “user-friendly” for the clinician, the patient and the radiologist. It is readily available, very fast, produces high- quality images, and is capable of detecting a wide array of illnesses. The typical CT radiation dose is 10 to 20 millisieverts (mSv), which is associated with a lifetime risk of fatal cancer of approximately one per 2,000 CT scans. The radiation exposure from three or four CT scans is roughly equivalent to that experienced by atomic bomb survivors in Japan who were located one to two miles from “ground zero.” 9 Although this startling figure has been questioned due to differences in the type and duration of radiation exposure, 10 it could well serve as a powerful argument to convince a patient to forgo a CT scan that the physician felt was truly unnecessary. Nonetheless, in EM practice, CT scans clearly provide potentially life-saving information for more than one in 2,000 patients. 11 The radiation dose and risk of malignancy vary Volume IX, no . 2 : May 2008