Effects of injection rates of contrast material on arterial phase hepatic CT

Our goal was to assess the effects of the i.v. injection rate of contrast material on arterial phase hepatic CT.

One hundred patients were randomly divided into four groups of 25 with different injection rates of 90 ml of contrast material: 2, 3, 4, or 5 ml/sec. Single-level serial CT was performed at the level of the middle section of the main portal vein before injection and every 2 sec from 12 sec to 60 sec after injection of contrast material. The enhancement value was calculated as the difference in attenuation value between the unenhanced and contrast-enhanced images for the aorta and liver parenchyma. The duration of the arterial phase was defined as the interval beginning when the enhancement value for the aorta reached 100 H and ending when the value for the liver parenchyma reached 20 H.

Faster injection rates increased the maximum enhancement of the aorta. Although faster injection rates decreased the time from injection to the beginning and the end of the arterial phase, faster injection rates did not decrease the duration of the arterial phase itself.

A faster injection rate increases arterial enhancement of the liver, and the duration of the arterial phase remains the same as that occurring with a slower injection rate. We hypothesize that faster injection rates can provide better results using CT to reveal hypervascular liver tumors.