[Optimal dosage of contrast material in screening upper abdominal enhanced CT]

To examine the possibility of decreasing the amount of intravenous contrast materia for screening upper abdominal CT scanning.

Eighty-seven patients(53 men and 34 women; 56.0 +/- 15.7 y.o.; range 20-88 y.o.; body weight 57.6 +/- 11.1 kg, range 29-85 kg) were randomly divided into two groups according to the amount of i.v. contrast material: 100 ml independent of patient weight(group 1) and 2 ml/kg (group 2). In both groups, contrast material(Iopamiron 300 mgI/ml) was intravenously administrated at an infusion speed of 1.5 ml/sec. Spiral scanning was started 90 sec after the start of contrast material injection. CT numbers of the portal vein, hepatic parenchyma of the right lobe, and background were measured on pre- and postenhanced images, and the contrast-to-noise ratio(CNR) and increases in CT the number of the right hepatic lobe(CNIliver) and portal vein(CNIportal) were calculated.

In group 1, patient's weight showed negative linear correlations with CNR(r = 0.442, p = 0.0027), CNIliver(r = 0.422, p = 0.0043), and CNIportal(r = 0.509, p = 0.00042). In group 2, such correlations were not observed.

Contrast enhancement in screening upper abdominal CT was negatively correlated with patients' weight in the group of contrast material injected with 100 ml.