What is the recommended protocol for an MRI of the liver?

MRI Liver Protocol

The recommended protocol for liver MRI is a multiphase contrast-enhanced study using gadolinium-based contrast agents, with imaging performed during dynamic phases (arterial, portal venous, and equilibrium at 15-120 seconds) followed by hepatocyte phase imaging at 20 minutes post-injection when using hepatobiliary agents like gadoxetate disodium. 1

Contrast Agent Selection

• Hepatobiliary agents (gadoxetate disodium/EOVIST) are preferred over extracellular gadolinium agents because they achieve 95-99% accuracy for hemangioma diagnosis, 88-99% accuracy for focal nodular hyperplasia, and 97% accuracy for hepatocellular carcinoma, compared to 91-95%, 85-93%, and 96-99% respectively with standard CT protocols. 1

• Gadoxetate-enhanced MRI establishes a definitive diagnosis in 95% of liver lesions versus 71% with contrast-enhanced CT, and only 1.5% of patients require additional imaging after MRI compared to 10% after CT. 1

• The combination of diffusion-weighted imaging (DWI) and hepatobiliary phase (HBP) imaging allows correct classification of lesions as benign or malignant in 91% of cases and exact characterization in 85% of cases. 1

Standard Imaging Protocol

Pre-Contrast Sequences

• Perform baseline pre-contrast MRI sequences before administering any contrast agent. 2

Contrast Administration

• Administer gadoxetate disodium at 0.025 mmol/kg body weight (0.1 mL/kg) as an undiluted intravenous injection at 1-2 mL per second. 2
• Flush the intravenous line with normal saline after injection. 2

Dynamic Phase Imaging

• Begin arterial phase imaging 15-25 seconds after completing the injection. 2
• Obtain portal venous phase at approximately 60 seconds post-injection. 2
• Acquire blood equilibrium phase at approximately 120 seconds post-injection. 2

Hepatocyte Phase Imaging

• Begin hepatocyte phase imaging at 20 minutes post-injection, which can be extended up to 120 minutes if needed. 2
• For patients with elevated bilirubin (>3 mg/dL) or ferritin levels, complete all imaging within 60 minutes post-injection, as these conditions reduce hepatic contrast effect. 2

Essential Sequences to Include

• Diffusion-weighted imaging (DWI) should be incorporated, though apparent diffusion coefficient (ADC) values show considerable overlap between benign and malignant solid lesions, limiting its standalone diagnostic value in patients without known malignancy. 1

• MR cholangiopancreatography (MRCP) sequences should be added when evaluating cholangiocarcinoma or biliary pathology. 1

Clinical Context Modifications

For Cirrhosis/Chronic Liver Disease

• Use the Liver Imaging Reporting and Data System (LI-RADS) algorithm with triple-phase contrast imaging (arterial, portal venous, delayed phases). 3
• Lesions ≥10 mm are required for definitive HCC diagnosis by imaging alone; smaller lesions require surveillance. 3

For Known Extrahepatic Malignancy

• The standard multiphase protocol remains appropriate, as it distinguishes metastases from benign lesions with high accuracy. 3

For Primary Sclerosing Cholangitis Screening

• Perform yearly contrast-enhanced MRI for cholangiocarcinoma screening. 1
• If initial MRI was performed without contrast, repeat with contrast enhancement within 6 months of PSC diagnosis. 1

Critical Safety Considerations

• Screen for chronic kidney disease (GFR <30 mL/min/1.73m²) or acute kidney injury before administering gadolinium, as these conditions increase nephrogenic systemic fibrosis (NSF) risk. 2
• For patients over 60 years or with hypertension/diabetes, estimate GFR through laboratory testing before contrast administration. 2
• Avoid gadolinium-based contrast agents in patients with severe renal impairment unless diagnostic information is essential and unavailable through non-contrast MRI. 2

Common Pitfalls to Avoid

• Do not perform MRI without IV contrast as the primary study for indeterminate lesions >1 cm, as it has insufficient diagnostic accuracy and is based only on expert opinion rather than evidence. 1

• Lesions with minimal hepatocyte function (cysts, metastases, most HCCs) will not accumulate gadoxetate, but well-differentiated HCC may show enhancement in hepatocyte phase, requiring additional clinical correlation. 2

• Do not use Tc-99m sulfur colloid scans, as they have no role in modern evaluation of indeterminate liver lesions. 3

• Inflammatory adenomas can mimic focal nodular hyperplasia on MRI, representing a diagnostic challenge that may require biopsy if clinical suspicion is high. 1