Radiation Risk of Body CT: What to Tell Our Patients and Other Questions

Abstract

Editor: The statistical analysis of radiation risk associated with screening computed tomography (CT) by Drs Brenner and Elliston in the September 2004 issue of Radiology (1) raises a number of serious questions. 1. The authors argue the risk of dying from a radiationinduced cancer to be 0.08% from a single whole-body screening CT examination, with the majority of the risk coming from lung cancer inductions. They point out that this is greater than the risk of dying in a traffic accident, though they do not compare it with the risk of dying of cancers that might be found in a screening CT examination. 2. While the authors compare the radiation dose of screening CT with that of mammography, a screening study with which it does not compete, they do not compare it with the radiation dose of barium enema, a screening technique that the American College of Radiology supports in the early detection of colon cancer with which CT colonography competes directly. Is a screening whole-body CT examination associated with more or less radiation exposure than a double-contrast barium enema with 3 minutes of fluoroscopy time and acquisition of eight overhead abdominal radiographs? How does the risk of death associated with radiationinduced cancers from screening whole-body CT compare with the risk of death associated with screening colonoscopy (after adjusting for the fact that deaths from colonoscopyinduced bowel perforation or conscious sedation complications occur acutely, not after many years)? 3. At root, radiation risk does not distinguish screening CT from standard CT, which makes up a large component of every radiologist’s practice. The studies are instead distinguished by how the patient arranged for the study: Did he or she desire it themselves, or was it ordered by a referring physician? If anything, screening CT may be associated with less radiation risk, because some screening CT protocols, especially for lung cancer, involve lower than standard radiation dose. So if a single screening CT examination of the body causes radiation exposure in the ballpark of that created by standing 1 mile away from the Hiroshima and Nagasaki atomic bomb attacks (as a newspaper summary of the authors’ article reports), what should we be telling our patients, by way of informed consent, about the risks of routinely ordered CT?