Aim of study: To analyze different protocols for spiral-CT with regard to the enhancement of liver parenchyma and vessels of the upper abdomen. To compare the achieved density values with those obtained by conventional CT.
Methods: 30 CT-examinations of the abdomen of different patients with normal findings of the liver were selected. In all examinations the upper abdomen was scanned before injection of contrast agent in conventional technique. In 10 patients spiral-CT of the liver was performed in the arterial phase at a delay of 15 sec and a flow of 4 ml/sec with 100 ml contrast agent, in 10 other patients in the portal-venous phase at a delay of 35 sec and a flow of 4 ml/sec with 100 ml contrast agent, followed by a spiral-CT of the upper abdomen in the arterial-venous phase at a delay of 70 sec and a flow of 1 ml/sec with 85 ml contrast agent. In 10 patients conventional CT of the upper abdomen was performed at a delay of 30 sec and a flow of 1 ml/sec with 200 ml contrast agent.
Results: The highest density of the aorta was achieved by the arterial spiral-CT (p < 0.001). In the portal-venous spiral-CT the density of liver parenchyma was lower than in the arterial-venous spiral-CT and conventional CT (p < 0.001). Both arterial-venous spiral-CT and conventional CT achieved the same contrast in the aorta (216 +/- 10 vs. 217 +/- 23 HE) and in liver parenchyma (110 +/- 3 vs. 112 +/- 16 HE), but arterial-venous spiral-CT showed a lower density in the inferior vena cava than conventional CT (138 +/- 9 vs. 162 +/- 21 HE) (p < 0.002).
Conclusions: The spiral-CT-protocol for the examination of the liver in arterial and arterial-venous phase enables a reliable and adequate enhancement of liver parenchyma and all vessels of the upper abdomen with a lower dose of contrast agent than is possible with conventional CT. Together with unenhanced CT, this protocol promises a better detection of focal lesions of the liver with different enhancement modes in the arterial and venous phases.