CHICAGO – Newer CT technology that can capture an image of a beating heart in a single beat may offer one way of reducing a patient's exposure to excess radiation, U.S. researchers said on Tuesday.
They said patients who got a type of heart scan called coronary angiography using the newer CT scanner technology received 91 percent less radiation than those who were scanned the traditional way using a computed tomography or CT scanner.
"The amount of radiation that a patient would receive is about a 10th of that as compared to using the most traditional protocol," Dr. Andrew Einstein of Columbia University Medical Center in New York, whose study appears in the journal Radiology, said in a telephone interview.
Radiation exposure from medical scans became a major concern of patients and lawmakers last fall after more than 200 patients were exposed to excess radiation during brain scans at Cedars-Sinai Medical Center in Los Angeles.
DOSE REDUCTION
Although heart CTs only accounted for 2.3 million out of 65 to 70 million CT scans performed in 2006, they are worrisome because they deliver high radiation doses, Einstein said.
"Since these are relatively high-dose tests, the ability to reduce the dose is a good thing," he said.
Heart CTs offer a noninvasive way to look for blockages in heart arteries. Traditionally, most of these patients get an angiogram, in which a thin tube is inserted into heart arteries but not all patients are good candidates for this.
Einstein and colleagues wanted to see how newer scanners that can capture a heart beat in a single scan compare to older, more time-consuming methods in terms of radiation dose.
For the study, he used the Toshiba Aquilion ONE scanner, which has the single heart beat feature but can also do conventional CT scans in which the scanner spirals around a patient.
When they compared the radiation dose between the two, they found the single heart beat approach cut the radiation dose from 35.4 millisieverts to 4.4 millisieverts.
By comparison, the average American is exposed to about 3 millisieverts of radiation a year from ground radon or flying in an airplane — a level not considered a risk to health.
"I think patients should take away from this, there are dose-reduction methods available which are not necessarily applicable to every single patient. For patients with fast heart rates, we can't use these lowest dose methods.
"But for many patients, there are dose-reduction methods available which can substantially reduce the amount of radiation they would receive from these tests," he said.
Einstein said the Toshiba scanner has a large detector that can cover the whole heart. It is one of two with the single heart beat feature.
A CT scanner made by Siemens called the Somatom Definition Flash spirals quickly around a patient to capture an image in a single heart beat.
Earlier this month, the U.S. Food and Drug Administration said it will issue new requirements for makers of CT scanners and other imaging devices to safeguard patients from excess exposure to radiation.
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