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Weighing Benefit, Risk Of Radiation Tests Urged

Ruzanna Harutyunyan's picture

Heart scans such as computed tomography (CT) scans should be used judiciously to minimize exposure to ionizing radiation, according to an American Heart Association science advisory published in Circulation: Journal of the American Heart Association.

View the full advisory here

One source of ionizing radiation is diagnostic tests that use X-rays such as computed tomography (CT), fluoroscopy (a video X-ray such as an angiogram), or nuclear medicine studies. There has been some concern about the relationship between low-dose ionizing radiation (the kind used in medical imaging) and cancer. While the risks are low, there is still uncertainty as to the exact level of risk. With the use of imaging on the rise, particularly cardiac imaging, the association saw the need to advise practitioners on the prudent use of medical imaging exams.

Facts about ionizing radiation:

• Medical imaging is the largest controllable source of radiation exposure to the U.S. population, and its most important determinant is the ordering healthcare provider.

• CT studies in 2006 accounted for about half of the medical radiation dose of the U.S. population.

• Among nuclear medicine studies in 2005, cardiac imaging represented 57 percent of the studies and accounted for about 85 percent of the radiation dose.

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• Medical imaging that uses X-rays is growing by 5 percent to 10 percent per year.

The recommendations for physicians:

• Cardiac imaging studies that expose patients to ionizing radiation should be ordered only after thoughtful consideration of the potential benefit to the patient, and in keeping with established appropriateness criteria. However, medically appropriate examinations should not be avoided because of concerns regarding radiation dose.

• Healthcare 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.

There is no federal regulation of radiation dose, except for mammography, according to the advisory. Therefore, the appropriate use of equipment and radiation dose is up to the imaging facility and physician. The purpose of the advisory is to make general recommendations for the safe use of cardiac imaging that uses ionizing radiation. However, "It is crucial that the potential relationship between low-dose radiation and cancer be characterized appropriately," said Thomas C. Gerber, M.D., Ph.D., lead author of the advisory and associate professor of medicine and radiology at the Mayo Clinic College of Medicine in Jacksonville, Fla.

The advisory notes that when speaking to patients about the risk of developing malignancies as a result of exposure to ionizing radiation in medical imaging, it may be instructive to compare this risk to the risks of developing a malignancy or dying as a result of conditions or activities of everyday life. For example, the lifetime odds of dying from the radiation of a coronary angiography are 0.5 per 1000 people, whereas the risk of dying from a natural fatal cancer is 212 per 1000 people, and the risk of death from passive cigarette smoke for someone married to a smoker is 10 per 1000 people.



Radiation exposure from cardio imaging using radioactive dyes that bind to healthy heart cells must be outlawed since it does more damage than good. Why? The radiation exposure to the heart and adjacent isues from radiation decay over about 1 month (for radio thallium) has been estimated at equivalent to more than 500 chest rays. And imaging requires binding of the dye to healthy or weakened heart tissue cells adjacent to damaged or dead cells from an infarct, thus further zapping healthy heart cells and potentially increasing the size of the infarct. There is no need for radio imaging since essentially the same information could be obtained from less expensive, non-invasive and briefer echocardiograms before and after a treadmill stress test. The main beneficiaries are the providers of this costly test requiring nearly 6 hrs and surgeons performing more bypass surgeries due to such hazardous diagnostic testing. H. Rutner, M.S., former radiation safety officer