Purpose To develop a dual-energy contrast media-enhanced computed tomographic (CT) protocol by using time-attenuation curves from previously acquired perfusion CT data and to evaluate prospectively the relationship between iodine enhancement metrics at dual-energy CT and perfusion CT parameters in patients with hepatocellular carcinoma (HCC). Materials and Methods Institutional review board and local ethics committee approval and written informed consent were obtained. The retrospective part of this study included the development of a dual-energy CT contrast-enhanced protocol to evaluate peak arterial enhancement of HCC in the liver on the basis of time-attenuation curves from previously acquired perfusion CT data in 20 patients. The prospective part of the study consisted of an intraindividual comparison of dual-energy CT and perfusion CT data in another 20 consecutive patients with HCC. Iodine density and iodine ratio (iodine attenuation of the lesion divided by iodine attenuation in the aorta) from dual-energy CT and arterial perfusion (AP), portal venous perfusion, and total perfusion (TP) from perfusion CT were compared. Pearson R and linear correlation coefficients were calculated for AP and iodine density, AP and iodine ratio, TP and iodine density, and TP and iodine ratio. Results The dual-energy CT protocol consisted of bolus tracking in the abdominal aorta (threshold, 150 HU; scan delay, 9 seconds). The strongest intraindividual correlations in HCCs were found between iodine density and AP (r = 0.75, P = .0001). Moderate correlations were found between iodine ratio and AP (r = 0.50, P = .023) and between iodine density and TP (r = 0.56, P = .011). No further significant correlations were found. The volume CT dose index (11.4 mGy) and dose-length product (228.0 mGy · cm) of dual-energy CT was lower than those of the arterial phase of perfusion CT (36.1 mGy and 682.3 mGy · cm, respectively). Conclusion A contrast-enhanced dual-energy CT protocol developed by using time-attenuation curves from previously acquired perfusion CT data sets in patients with HCC could show good correlation between iodine density from dual-energy CT with AP from perfusion CT. (©) RSNA, 2016.