AJR: Lower contrast dose maintains CTA image quality
Reducing the contrast media dose in coronary CT angiography (CTA) limits risks while not significantly affecting the quality of images, according to a study published in the October issue of the American Journal of Roentgenology.

Researchers wanted to evaluate the difference in coronary enhancement provided by 60 mL of iopamidol contrast medium (370 mg l/mL), compared with the more common dose of 80 mL, when conducting a prospectively ECG-gated single-heartbeat axial 320-slice CT scan.

The results showed that while there was less coronary enhancement with the reduced contrast medium dose, more than 96 percent of coronary segments still had sufficient enhancement based on region-of-interest attenuation (HU) measurements.

“Many centers currently use a higher iodine load comparable or equal to 80 milliliters of iopamidol,” Frank Rybicki, MD, of Brigham and Women’s Hospital in Boston, said in a statement. He said the study shows this higher dose “is not necessary, and the extra contrast means unnecessary costs and increased risk of contrast-induced nephropathy (CIN) to the patients.”

The researchers retrospectively evaluated 108 consecutive 320-slice CTA studies and separated them into groups. Group 1 consisted of 36 patients who received 60 mL of an iodinated contrast medium and group 2 consisted of 72 patients who received 80 mL. All patients were imaged with a standardized protocol. Two imagers then subjectively assessed image quality throughout the coronary arteries, performing HU measurements in the aorta plus the proximal and distal coronary arteries.

This subjective analysis showed group 2 had better image quality with significantly higher mean HU. Nevertheless, 96.7 percent of all coronary segments in group 1 patients had an attenuation of greater than 300 HU, which was deemed a sufficient level of enhancement.

Even when separating out larger patients, 60 mL offered sufficient enhancement in most cases. Of the patients with a body mass index of more than 30, 92.8 percent of the segments had attenuation values of 300 HU, and all segments measured more than 250 HU.

“These results support the general use of 60 milliliters of iopamidol for CT angiography done on 320 detector row CT scanners,” Rybicki said in the statement.