About 400,000 of those patients receive very high doses, more than the maximum annual exposure allowed for nuclear power plant employees or anyone else who works with radioactive material.
It did not estimate the number of cancer cases that the radiation might cause over the next several decades. A researcher studied the use of medical imaging, said it would probably result in tens of thousands of additional cancers.
Each individual patient is at relatively minor additional risk from the tests, but because they are given to so many people, the cumulative risk is significant.
“It’s certain that there are increased rates of cancer at low levels of radiation, and as you increase the levels of radiation, you increase cancer, which was not connected with the new study.
The radioactive tests are given for hundreds of purposes. In the last two decades, they have become especially common in cardiology, where physicians use them to check for the buildup of plaque in the arteries and the heart’s ability to pump blood.
Some cardiologists now encourage their patients to have routine heart scans even if they do not have clinical symptoms of heart disease, like chest pain or shortness of breath. The study did not examine what percentage of the tests was medically necessary.
The use of the tests has risen sharply in the last two decades, as more and more physicians have bought CT and PET scanners and installed them in or near their offices.
The researchers calculated the amount of radiation received by the patients by looking at insurance codes for various kinds of imaging tests. Exposure is measured in millisieverts.The paper found that in at least one of the three years, 1.9 percent of the United Healthcare patients received at least 20 millisieverts of radiation, or nearly seven times the average. Of that group, about 10 percent, or 0.2 percent of all patients, received at least 50 millisieverts, more than the annual maximum that nuclear regulators allow.
In many cases, there is little evidence that the routine use of scans helps physicians make better decisions, especially in cases where the treatments that follow are also of questionable efficacy.
Were we to insist that all, or nearly all, procedures be studied in well-designed trials, we could answer many critical clinical questions.
Until then, patients and physicians should discuss the risk of the tests and keep close track of the overall radiation dose that patients are receiving, he wrote, adding, “We have to think and talk explicitly about the elements of danger in exposing our patients to radiation.”
- By Zane Wylie
