Assessment of the Use of a Saline Chaser to Reduce the Volume of Contrast Medium in Abdominal CT

Abstract

The purpose of this study was to investigate, first, the effect on enhancement of the liver and aorta during abdominal CT of the use of saline solution as a partial substitute for or in addition to contrast medium when the dose of medium is determined by the patient's body weight and, second, whether use of a saline chaser allows a decrease in the dose of contrast medium to less than 1.5 mL/kg. We enrolled 407 patients undergoing abdominal exploration on MDCT, including an early arterial phase and a portal phase. Group 1 received contrast medium at a dose of 1.5 mL/kg. Group 2 received contrast medium at a dose of 1.5 mL/kg less 20 mL of iodine followed by 30 mL of saline solution. Group 3 received the full 1.5 mL/kg dose of medium followed by a 30-mL saline chaser. Attenuation values were obtained from the aorta in the arterial phase and from the liver in the portal phase. The groups were comparable in mean body weight and heart rate. None of the differences between them in aortic enhancement in the early arterial phase were statistically significant (group 1, 206 +/- 3 H; group 2, 204 +/- 3 H; group 3, 209 +/- 4 H). There was a negative correlation between weight and aortic enhancement (r = -0.42, p < 0.0001) and a positive correlation between weight and hepatic enhancement (r = 0.19, p < 0.0001). A significant reduction (p = 0.0002) in hepatic enhancement was observed in group 2 (group 1, 53 H; group 2, 46 H; group 3, 54 H). Hepatic enhancement greater than 45 H was observed in all groups except for the group 2 subgroup of patients weighing less than 55 kg. In MDCT, reducing the amount of contrast medium does not affect aortic enhancement in the early arterial phase but decreases hepatic enhancement at the portal phase. The saline chaser technique had no influence on the phases studied. Greater than 1.5 mL/kg reduction in the dose of contrast medium followed by saline flushing may not be advisable for liver CT in low- and medium-weight patients.