Efficacy of the iodine-free computed tomography liver contrast agent, Dy-EOB-DTPA, in comparison with a conventional iodinated agent in normal and in tumor-bearing rabbits.

RATIONALE AND OBJECTIVES

To investigate the efficacy of the new liver-specific x-ray contrast agent, Dy-EOB-DTPA, in rabbits with VX2 liver tumors by spiral computed tomography (CT) in comparison to iopromide.

MATERIALS AND METHODS

The time course of liver enhancement was determined in five groups of two normal anesthetized rabbits, which received intravenous injections of Dy-EOB-DTPA before anesthesia at a dose of 0.5 mmol/kg. Fifteen, 30, 45, 60, and 90 minutes after administration spiral CT images were obtained and the attenuation in the livers were determined. A second group of ten rabbits with implanted VX2 tumors received in a random crossover design either Dy-EOB-DTPA at a dose of 0.5 mmol/kg or, 1 day later, iopromide at a dose of 600 mg iodine/kg. CT images were obtained 60 minutes after Dy-EOB-DTPA administration and both in the arterial and portal-venous phases after iopromide injection. Three radiologists evaluated the images. The rabbits were killed, and their livers were investigated histologically for liver tumors.

RESULTS

In normal animals, 0.5 mmol/kg Dy-EOB-DTPA resulted in a liver enhancement of 30 HU during the whole observation period of 90 minutes. In tumor-bearing animals, histology revealed 14 implanted tumors of 3-20 mm diameter. Sixty-five percent of the tumors were below 10 mm. Dy-EOB-DTPA was able to detect 13 tumors (93%), iopromide 11 (79%) both in the arterial and in the portal-venous phase. The difference was statistically not significant. In plain CT, seven tumors (50%) were found (P < 0.01 vs iopromide and Dy-EOB-DTPA). One scar and two sites of necrosis were detected by each of the methods.

CONCLUSION

Dy-EOB-DTPA injection at a dose of 0.5 mmol/kg resulted in a long-lasting detectability of 93% of all implanted tumors versus 79% found with iopromide.