What is the recommended MRI protocol for evaluating liver adenoma?

MRI Protocol for Evaluating Liver Adenoma

For optimal evaluation of liver adenoma, a dedicated liver MRI with hepatobiliary contrast agent (gadoxetic acid) is strongly recommended as the first-line imaging modality. 1

Recommended MRI Protocol Components

Basic Sequences

• T1-weighted sequences (in-phase and out-of-phase)
• T2-weighted sequences with and without fat saturation
• Diffusion-weighted imaging (DWI)

Contrast Administration

• Hepatobiliary contrast agent (preferably gadoxetic acid/Gd-EOB-DTPA)
• Dynamic multi-phase imaging including:
  • Pre-contrast phase
  • Arterial phase
  • Portal venous phase
  • Delayed phase
  • Hepatobiliary phase (20 minutes after contrast administration)

Technical Considerations

• High-resolution imaging with thin slices (≤5mm)
• Coverage of the entire liver
• Multi-planar acquisitions (axial primary, with coronal and sagittal reformats)

Rationale for Protocol Selection

MRI is superior to other imaging modalities for evaluating liver adenomas due to:

1. Superior soft tissue contrast - MRI provides better differentiation between adenomas and other focal liver lesions 1
2. Multiparametric capabilities - Combination of T1, T2, DWI, and dynamic contrast enhancement allows comprehensive characterization 1
3. No ionizing radiation - Particularly beneficial for patients requiring repeated surveillance imaging 1

Importance of Hepatobiliary Contrast Agents

Hepatobiliary agents like gadoxetic acid are particularly valuable for adenoma evaluation because:

• They allow for both dynamic contrast images and hepatobiliary phase images 1
• Adenomas typically show enhancement in the arterial phase but appear hypointense compared to surrounding liver in the hepatobiliary phase (91% of cases) 2
• This enhancement pattern helps differentiate adenomas from focal nodular hyperplasia (FNH), which typically appears hyperintense in the hepatobiliary phase 2

Specific Features to Evaluate

When interpreting MRI for liver adenoma, focus on:

1. Signal characteristics:

   • Heterogeneous signal intensity (present in 29/31 adenomas) 3
   • Variable T1 signal, often predominantly hyperintense on T2-weighted images 3

2. Enhancement pattern:

   • Early arterial enhancement (present in 13/15 adenomas) 3
   • Variable washout in portal venous phase 2
   • Hypointense appearance in hepatobiliary phase (91% of cases) 2

3. Specific pathologic features:

   • Intratumoral hemorrhage
   • Large intratumoral vessels
   • Fatty change
   • Peliosis (blood-filled cavities) 3

Common Pitfalls and Caveats

1. Inflammatory adenomas may show atypical enhancement patterns, with up to 26% showing predominant hyperenhancement on hepatobiliary phase images, potentially mimicking FNH 4

2. Heterogeneity in appearance due to varied histologic components can make definitive diagnosis challenging 3

3. Size and number assessment is critical for management decisions and should be carefully documented

4. Renal function evaluation is necessary before administering gadolinium-based contrast agents, particularly in patients with severe renal dysfunction due to risk of nephrogenic systemic fibrosis 1

By following this protocol, clinicians can obtain comprehensive imaging information to accurately diagnose and characterize liver adenomas, which is essential for appropriate management decisions.