Effect of injection rate of contrast medium on pancreatic and hepatic helical CT

PURPOSE: To assess the effect of the injection rate of contrast medium on pancreatic and hepatic enhancement at abdominal helical computed tomography (CT). MATERIALS AND METHODS: Sixty-four contrast medium-enhanced abdominal helical CT scans (64 adult patients) were obtained with 150 mL of contrast medium. The injection rate was 2.5 mL/sec for the first 32 scans and 5.0 mL/sec for the remaining 32. Scans were obtained at 5-sec intervals, with an intermediate 8-sec breathing interval, Hepatic and pancreatic enhancement levels were measured and averaged, and time-attenuation curves were plotted for both groups. Differences in weight, age, time to peak pancreatic and hepatic enhancement, and peak enhancement were assessed with the Student t test. RESULTS: Both peak enhancement and time to peak enhancement were significantly different between the two injection rates (P less than or equal to .002), with faster, more intense hepatic and pancreatic enhancement at the higher rate. At 2.5 mL/sec, the pancreas reached a peak attenuation level of 65 HU at 69 sec, and the liver reached a peak of 58 HU at 87 sec. At 5.0 mL/sec, the pancreas reached a peak attenuation of 84 HU at 43 sec, and the liver reached a peak of 75 HU at 63 sec. CONCLUSION: Absolute values for and times to peak pancreatic and hepatic enhancement are directly related to the contrast medium injection rate.