MR Elastography Does NOT Require Contrast
MR elastography is performed without intravenous gadolinium-based contrast agents. The technique uses mechanical shear waves and phase-contrast MRI sequences to measure tissue stiffness, making contrast administration unnecessary for the elastography measurement itself 1, 2, 3.
How MR Elastography Works
MR elastography employs phase-contrast MRI sequences to visualize propagating mechanical shear waves that are externally introduced into tissue, allowing direct measurement of tissue stiffness without any contrast agent 2, 4, 3.
The technique measures displacement caused by mechanical waves and calculates material properties such as shear modulus from these measurements, functioning as "virtual palpation" or "palpation by imaging" 2, 4, 3.
MR elastography can be seamlessly incorporated into a standard MRI examination to provide rapid, reliable assessment at a single patient appointment 2.
When Contrast May Be Added (But Not for Elastography Itself)
If MR elastography is performed during the same session as conventional MRI for HCC screening, gadolinium contrast may be administered for the tumor detection component, but this contrast is for the conventional MRI sequences, not for the elastography measurement 1.
The ACR Appropriateness Criteria assign MR elastography a rating of 5 ("may be appropriate") when combined with MRI for HCC screening if there is simultaneous need for fibrosis diagnosis, but the elastography component itself does not require contrast 1.
Gadolinium-enhanced MRI sequences can show bands of fibrosis as linear areas of enhancement on delayed-phase imaging, but this represents conventional contrast-enhanced MRI, not MR elastography 1.
Important Clinical Distinctions
MR elastography has no role in diagnosing acute hepatic inflammation from various causes, as it is designed specifically for assessing chronic fibrosis and stiffness 1.
Liver stiffness measurements can be influenced by factors other than fibrosis, including edema, inflammation, extrahepatic cholestasis, and passive congestion, which are important confounders to recognize 1, 5.
MR elastography is currently the most accurate imaging modality for diagnosing and staging hepatic fibrosis, superior to both ultrasound elastography and conventional contrast-enhanced MRI 1, 5.
Common Pitfalls to Avoid
Do not confuse MR elastography with dynamic contrast-enhanced (DCE) MRI, which does require gadolinium and has been studied for fibrosis staging but is laborious and not clinically utilized 1.
Hepatic iron deposition can reduce MR elastography accuracy due to susceptibility artifacts, and performance may be compromised at 3-Tesla field strength 5.
Patients should be fasting when undergoing elastography (similar to ultrasound elastography), as recent food intake can confound liver stiffness measurements 1, 5.