Experts Urge Limits on Use of Cardiac CT Scans
MONDAY Feb. 2, 2009 -- Certain kinds of heart imaging tests should be used cautiously to minimize patient exposure to ionizing radiation, which has been linked to cancer.
That's the conclusion of a new American Heart Association science advisory released in the Feb. 2 issue of Circulation.
Sources of ionizing radiation include diagnostic tests that use X-rays -- such as computed tomography (CT), fluoroscopy (a video X-ray such as an angiogram) -- and nuclear medicine studies. Due to concerns about low-dose ionizing radiation and cancer risk, the AHA issued guidelines for physicians on the prudent use of medical imaging exams:
- Cardiac imaging studies that expose patients to ionizing radiation should be ordered only after thoughtful consideration of the potential benefits to the patient, and in keeping with established appropriateness criteria. However, medically appropriate examinations should not be avoided because of concerns regarding radiation dose.
- Health-care providers should diligently review patient records, including those from other medical institutions, to ensure that imaging studies are not needlessly repeated.
- Routine surveillance radionuclide stress tests or cardiac CTs in symptom-free patients at low risk for heart disease are not recommended.
- If a cardiac imaging study that uses ionizing radiation is needed, every effort should be made to reduce patient dose, while still maintaining image quality that is sufficient for confident interpretation of the exam.
According to the AHA, medical imaging is the largest controllable source of radiation exposure to people in the United States, and its most important determinant is the ordering health-care provider. In 2006, CT scans accounted for about half of the medical radiation dose of the U.S. population. The use of medical imaging that uses X-rays is increasing by 5 percent to 10 percent a year. In 2005, cardiac imaging accounted for 57 percent of nuclear medicine studies.
Other than mammography, there is no federal regulation of radiation dose in imaging tests. This means that the appropriate use of equipment and radiation dose is up to the physician and imaging facility, the AHA noted.
The advisory authors emphasized the low cancer risk associated with ionizing radiation in medical imaging. For example, the lifetime risk of dying from cancer caused by coronary angiography-associated radiation is 0.5 per 1,000 people. This is much lower than the risk of dying from a natural cancer (212 per 1,000 people) or from secondhand smoke-related cancer among nonsmokers married to a smoker (10 per 1,000).
The Health Physics Society has more about doses from medical radiation sources.
Posted: February 2009