Feasibility of computed tomography cholangiography using Gd-EOB-DTPA: a phantom study

Purpose: To assess the feasibility of computed tomography cholangiography (CTCG) using an hepatobiliary contrast agent for magnetic resonance imaging (Gd-EOB-DTPA). Material and Methods: We built three CT phantoms including a radiotransparent 2:1 scale representation of the extrahepatic and intrahepatic bile ducts up to the second order branches. By assuming standard contrast pharmacokinetics in an adult male patient of 70 kg, we filled phantoms with water and a volume of 4.05, 3.15 and 2.25 mL of 0.25 mmol/L concentrated Gd-EOB-DTPA, respectively. Volumes corresponded to the expected dose fraction (DF) of Gd-EOB-DTPA in the biliary tree given a i.v. dose to the patient (DP) of 9.0, 7.0 and 5.0 mL, respectively. Phantoms were scanned with a 64- row multidetector CT using a standardized protocol (120 kVp and 200-500 mA). We then performed a quantitative analysis by calculating the signal-tonoise ratio (SNR) of the biliary tree over the phantom background. Results: On visual analysis, the biliary tree phantoms appeared as hyperattenuating, regardless of contrast DF/DP. On quantitative analysis, the phantom with DF/DP = 3.15/7.0 mL, corresponding to the standard patient dose, showed average SNR (6.51) similar to that of the 2.25/5.0 mL phantom (SNR=6.45), although lower than the DF/DP = 4.05/9.0 mL phantom (SNR=11.56). Conclusion: In our model, a standard i.v. dose of Gd-EOB-DTPA determines acceptable hyperattenuation of the biliary tree on CT.