RSNA: CCTA with gadolinium is alternative for those contraindicated for iodine
CHICAGO—Gadolinium-enhanced 64-slice coronary CT angiography (CCTA) could be an alternative to rule out coronary stenosis in patients with contraindications to iodine contrast, based on a study presented Nov. 28 at the 96th annual Radiological Society of North America (RSNA) conference.

Carlos M. Capunay, MD, from Diagnóstico Maipú in Buenos Aires, Argentina, who presented the study, said he and his colleagues sought to evaluate the image quality and contrast enhancement of gadolinium-enhanced 64-slice multidetector CT angiography for the assessment of coronary artery disease.

In the study, 23 patients with suspected coronary artery disease were consecutively enrolled with gadolinium-enhanced 64-slice multi-slice CT (Brilliance 64, Philips Healthcare). The technical parameters used were 64 x 0.625 mm collimation, 0.675mm slice thickness, 0.3mm reconstruction interval, 0.2 pitch, 120kV, 800mAs. A maximum dose of up to 0.4 mmoL/kg of body weight of gadolinium was injected at a rate of 6mL/sec followed by 40mL of saline injection at a rate of 4 mL/sec.

Capunay and colleagues triggered scanning once contrast material reached a density equal to or greater than 80 HU at the left atrium. They administered oral beta-blockers to all patients whose heart rate was above 60 beats per minute (bpm), 24 to 48 hours prior to the study.

The researchers determined three measurements in each patient at the level of the ascending aorta (initiation of the scan), aortic root and the descending aorta. Image quality was classified as:
  1. Excellent: If there was adequate coronary opacification with no artifacts;
  2. Good: Adequate coronary opacification with artifacts in less than two coronary segments;
  3. Average: Poor coronary opacification with artifacts in less than two segments; and
  4. Inadequate: Poor coronary opacification with artifacts in more than two segments.

They analyzed segments with a diameter greater than 1.5 mm, and checked the serum creatinine levels in each of the patients, according to Capunay.

The average heart rate during the scan was 53 bpm. The researchers reported no patients had “poor image quality.” There were 16 patients with excellent, four patients with good and three patients  with average quality. The mean level of enhancement was 196 HU at the ascending aorta, 199 HU at the aortic root and 178.3 at the descending aorta.

Capunay noted that there were no complications in the patients and no reports of symptoms related to nephrogenic systemic fibrosis. Based on the findings, he concluded that 64-slice CCTA with gadolinium contrast is “technically feasible” and allows radiologists to obtain adequate enhancement for a selected subset of patients.

However, Capunay acknowledged that the small size of the patient population was a limitation. Also, lack of data with regard to accuracy is also a limitation to the findings; he mentioned that he and his colleagues are "working on gathering" accuracy data.