Aortic enhancement during abdominal CT angiography: Correlation with test injections, flow rates, and patient demographics

Abstract

OBJECTIVE. The goal of our study was to determine the effect of contrast material injection rate and patient demographic variables on vascular enhancement for abdominal CT angiography and compare test injection results with actual patterns of vascular enhancement. SUBJECTS AND METHODS. One hundred twenty-five patients underwent abdominal CT angiography. For each patient, CT attenuation values (Hounsfield units) of the aorta were determined before and after IV contrast administration, every 3 sec between 21 and 60 sec. A peak aortic enhancement value and the time needed to reach peak and aortic enhancement thresholds of 150 and 200 H were determined. All patients received 150 ml of nonionic contrast material at 3 ml/sec in 25 patients and 4 ml/sec in 100 patients. A test injection of 15 ml was used to compute a scan delay in 46 patients. Patient age, sex, weight, injection rate, and test injection results were compared with vascular enhancement patterns. RESULTS. For the 125 patients, the mean aortic enhancement at each time point was greater than 150 H. Patient weight was inversely correlated (r2 = -.62) with aortic enhancement. The test injection did not accurately predict actual aortic enhancement peak value or time. Test injection delay time was significantly correlated with time to reach aortic enhancement thresholds of 150 and 200 H. The 4 ml/sec rate resulted in a higher peak aortic enhancement (320 ± 58 H versus 281 ± 49 H) (mean ± SD, p