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Low-radiation CT coronary angiography as accurate as invasive studies

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – Prospective ECG-triggering during computed tomography (CT) scanning of the heart can substantially reduce patients’ exposure to radiation while maintaining imaging accuracy close to that of invasive angiography, Swiss investigators report.

With prospective ECG-triggering, “radiation is administered at only one predefined end-diastolic time point instead of during a whole phase of the cardiac cycle,” Dr. Philipp A. Kaufmann and associates at University Hospital Zurich explain in the October 15 issue of Heart. This technique results “in a massive reduction in radiation exposure.”

In what the researchers call “the first head-to-head comparison” of radiation doses from invasive diagnostic angiography and low-dose 64-slice CT with prospective ECG-triggering, 42 patients with suspected coronary artery disease underwent both procedures.

The estimated mean effective radiation doses were 8.5 mSv (range 1.4-20.5 mSv) for invasive angiography and 2.1 mSv (range 1.0-3.3 mSv) for CT coronary angiography. Moreover, the mean effective radiation dose was significantly higher in the invasive coronary angiography group in all analyzed patients.

The authors note that 97% of segments analyzed were evaluable.

For detecting coronary artery narrowing of 50% or greater, CT coronary angiography had a sensitivity of 94.2%, specificity of 94.8%, positive and negative predictive values of 89.0% and 97.4%, respectively, and accuracy of 94.6%.

The investigators point out some technical limitations: image quality is affected by arterial calcification and body mass index, for example, and sinus rhythm and heart rate control are “mandatory.” Also, left ventricular function cannot be assessed because acquisition is limited to one phase.

Still, they emphasize, “Low-dose CT coronary angiography allows evaluation of coronary artery disease with high accuracy, but a significantly less effective radiation dose to patients compared to diagnostic invasive coronary angiography.”

They note as well that prospective ECG-triggering is “not limited to the 64-slice CT scanners but can be implemented into the latest…and future scanner generations.”

Heart 2009;95:1656-1661.