Americans who undergo heart tests may prevent themselves from advanced heart diseases, but not from excessive doses of radiation. A new study shows that compared to other countries, patients in the United States are often more exposed to increased radiation due to heart imaging studies.
A common American patient receives 20 percent higher radiation than another individual being treated outside of the U.S. Such a finding is due to the fact that most diagnostic facilities in the country do not comply with the recommended dosing guidelines, a group of international researchers said.
The recommended dose of radiation per patient during a heart test called myocardial perfusion imaging is 9 millisieverts (mSv) or less. In the new study, the authors found that only 24 percent of study subjects are able to meet this criteria. In other countries, this recommendation is being practiced in 43 percent of patients.
About 50 percent of the time, non-U.S. patients receive radiation doses of 9.7 mSv or below. In the U.S., however, the radiation dose is 11.6 mSv, half of the time.
To come up with their findings, the researchers obtained information from the International Atomic Energy Agency to evaluate the level of radiation involved in cardiology studies. They also studied protocols in 308 labs across 65 different countries, including 55 facilities in the U.S.
The investigators looked at whether the laboratories employ the recommended doses by performing techniques such as lessening radioactive tools, providing treatment based on patient weight and using the least possible amount of nuclear medicine.
Nuclear medicine is only given in additional doses for patients whose "stress-only" imaging results suggest a problem. Those who exhibit normal results at the initial testing need not to undergo another round of nuclear medicine. Complying to such protocol was found to reduce radiation dose by 64 percent or from 11 mSv to 4 mSv on the average.
Majority of labs in the U.S. do not use thallium in patients aged 70 years old and below. Such finding may seem promising as the chemical element is an agent that exposes patients to higher amounts of radiation. However, this is dragged down by the fact that only few facilities adjusted doses based on weight and minimized nuclear medicine in stress tests.
Researchers found minimal links between nuclear imaging and cancer risk. They also said that heart disease poses far more serious effects than heart-test-induced radiation exposure. Despite this, study co-author Andrew J. Einstein said their findings still stress the important role of doctors in lessening radiation exposure.
"Physicians independently decide when to order tests and determine how they are performed," wrote Rebecca Smith-Bindman of the University of California, San Francisco in an accompanying editorial. She added that the correct tests can diagnose disease earlier and more accurately, thereby paving the way for better treatment and prognosis.
Smith-Bindman also said that unnecessary tests can cause patients to suffer from different consequences such as physical discomfort, anxiety, development of irrelevant incidental findings and exposure to hazardous radiation.
The study was published in JAMA Internal Medicine on Monday, Dec. 28.
Photo: Dina-Roberts Wakulczyk | Flickr
