AJR: Quality still good in low dose coronary CTA scan in non-obese patients

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Radiologists can now lower the radiation dose delivered by coronary CT angiography (CCTA) by 39 percent in adult patients weighing 185 pounds or less, according to a study published in the April issue of the American Journal of Roentgenology.

Performed at the University of Erlangen in Erlangen, Germany, the study included 100 patients, weighing 185 pounds or less, who underwent CCTA either using a tube voltage of 120 kV or 100 kV.

A dual-source CT scanner (Siemens Healthcare) was used (330-milliseconds rotation, 0.6-mm collimation, 56 ± 7 mL of IV contrast agent at 5 mL/s). Each patient was randomized either to scanning protocol group 1 (120 kV and 330 mAs) or protocol group 2 (100 kV and 330 mAs). ECG pulsing was used for all patients. Data sets were assessed by two independent observers for image quality, signal-to-noise ratio, and contrast-to-noise-ratio. Effective dose was determined based on dose-length product.

Results showed that the effective radiation dose for patients scanned with 120 kV ranged from 8.8 to 16.9 mSv; the effective radiation dose for patients scanned with 100 kV ranged from 4.9 to 11.9 mSv. "At the same time, the overall image quality was preserved. Image quality scores using 120 kV were 2.7 plus/minus 0.5; scores using 100 kV were 2.6 plus/minus 0.4," said Tobias Pflederer, MD, lead author of the study.

The use of lower tube voltage leads to significant reduction in radiation exposure in noninvasive CCTA. Image quality in nonobese patients is not negatively influenced.

"The standard coronary CT angiography protocol uses the higher tube voltage value of 120 kV however our study shows that 100 kV can be used instead. It is important to keep the radiation dose as low as possible, especially in younger and female patients," said Pflederer.