RESULTS	During the second imaging phase , iodixanol at 320 mg I/ml and iodixanol at 300 mg I/ml provided significantly higher enhancement of the liver ( 75 H , 69 H , 62 H ) , aorta ( 144 H , 140 H , 122 H ) , and portal vein ( 147 H , 147 H , 118 H ) than did iopromide at 300 mg I/ml .\