Characterization of hepatic adenoma and focal nodular hyperplasia with gadoxetic acid

Abstract

Purpose: To characterize imaging features of histologically proven hepatic adenoma (HA) as well as histologically and/or radiologically proven focal nodular hyperplasia (FNH) using delayed hepatobiliary MR imaging with 0.05 mmol/kg gadoxetic acid.

Materials and methods: Five patients with six HAs with histological correlation were retrospectively identified on liver MRI studies performed with gadoxetic acid, and T1-weighted imaging acquired during the delayed hepatobiliary phase. Additionally, 23 patients with 34 radiologically diagnosed FNH lesions (interpreted without consideration of delayed imaging) were identified, two of which also had histological confirmation. Signal intensity ratios relative to adjacent liver were measured on selected imaging sequences.

Results: All six hepatic adenomas (100%), which had histological confirmation, demonstrated hypointensity relative to adjacent liver on delayed imaging. Furthermore, all of the FNH (including 34 radiologically proven, 2 of which were also histologically proven) were either hyperintense (23/34, 68%) or isointense (11/34, 32%) relative to the adjacent liver on delayed imaging. None of the FNHs were hypointense relative to liver.

Conclusion: Distinct imaging characteristics of HA versus FNH on delayed gadoxetic acid-enhanced MRI, with adenomas being hypointense and FNH being iso- or hyperintense on delayed imaging may improve specificity for characterization, and aid in the differentiation of these two lesions.

Figure 1

Imaging characteristics of a histologically proven HA in a 34-year-old woman with gadoxetic acid-enhanced MRI. The lesion is hyperintense on the late arterial phase contrast-enhanced T1w image (T1w dur, D), contains a significant amount of fat as demonstrated by dropout of signal on opposed phase imaging (C), and is slightly hyperintense on T2w imaging (A). Note the hypointensity of the lesion on delayed T1w hepatobiliary phase images at 20 minutes (T1w 20min, F) relative to the adjacent liver.

Figure 2

Another example of a histologically proven HA in a 21-year-old woman. The lesion demonstrates relatively intense arterial enhancement (C) and a central scar, making it difficult to distinguish from an FNH. However, note the marked hypointensity of the lesion compared to surrounding liver which was a common finding seen in all the hepatic adenomas.

Figure 3

Imaging characteristics of a histologically proven FNH in a 25-year-old woman with gadoxetic acid-enhanced MRI. The lesion is hyperintense on late arterial phase T1w imaging (B) with equalization in the portal venous phase (C) and isointensity on T2w imaging (A). Note slight hyperintensity of the lesion on delayed T1w hepatobiliary phase images at 20 minutes distinguishing it from hepatic adenoma. No central scar is present in this case.

Figure 4

Example of a radiologically diagnosed FNH with type 1 pattern of delayed enhancement on gadoxetic acid-enhanced MRI. The delayed uptake is overall uniform throughout the lesion, and the complex morphology of the lesion, including the presence of a central scar, matches that seen in the late arterial phase T1w image (C).

Figure 5

Example of a radiologically proven FNH with type 2 pattern of delayed enhancement on gadoxetic acid-enhanced MRI. Note an intense rim, brighter than the adjacent liver or central core (D). The central core is larger in extent than the central scar and is hypointense to both the peripheral rim and surrounding liver.

Figure 6

Example of a radiologically proven FNH with type 3 pattern of delayed enhancement on gadoxetic acid-enhanced MRI. Note a very intense rim, brighter than the adjacent liver or central core. The central core is larger in extent than the central scar and is hypointense to the rim but iso- to hyperintense to the adjacent liver.

Figure 7

Left: Schematic representation of the three observed FNH patterns (1, 2, 3). F = additional FNH’s; V = vessel. Right: Box plots show the distribution of enhancement pattern types in comparison to approximate lesion area on the image with largest lesion diameters (mm²). No correlation of enhancement pattern type and maximum size was seen, although the larger lesions tended to demonstrate type 1 delayed enhancement. For detailed statistics, please refer to Results section. Solid cube = median, stars = minimum and maximum value; diamonds next to box plots show the data distribution.