Optimization of hepatobiliary phase imaging in gadoxetic acid-enhanced magnetic resonance imaging: a narrative review

Background and Objective: Gadolinium ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) is widely used in clinical practice. Its unique hepatobiliary phase (HBP) has been used to improve the detection and identification of hepatic lesions and has also been used to evaluate hepatic function and fibrosis. At the early stage of its clinical practice, the HBP was typically collected empirically with a delay of 20 minutes after intravenous administration to image the liver with sufficient enhancement for diagnosis. However, numerous methods and consensus statements for optimizing HBP acquisition have been proposed. This review details the methods and consensus statements on optimizing HBP collection. Methods: The electronic literature search was performed using the databases PubMed, MEDLINE, Cochrane, and Embase without limit on publication period to identify published reports on optimizing HBP imaging in Gd-EOB-DTPA-enhanced MRI. Articles with low relevance to the topics were excluded. Key Content and Findings: Recently, an increasing number of investigations suggest that collecting HBP after 20 min is too drawn-out for patients with normal liver function but is too short for patients with cirrhosis. Previous studies demonstrated that liver enhancement is closely related to liver function in Gd-EOB-DTPA-enhanced MRI. Therefore several reports have proposed various HBP delay times at different liver function levels. These delay times could be evaluated by laboratory indicators, such as prothrombin (PT) activity, total bilirubin, direct bilirubin, and the model for end-stage liver disease. Other investigations have found that the initial visualization time of the intrahepatic bile duct (IHD) in Gd-EOB-DTPA-enhanced MRI to also be related to liver enhancement and function. Therefore, initial visualization of the IHD is considered necessary for adequate HBP and has been employed in HBP acquisition in recent reports. Conclusions: Optimizing HBP acquisition according to individual hepatic function is a good strategy and was followed in most of the investigations included in our review. Obtaining adequate HBP in the shortest possible time is the target condition in Gd-EOB-DTPA-enhanced MRI. However, a more concise and efficient HBP acquisition strategy is still expected to be developed in the future.