R₂* Impact on Hepatic Fat Quantification With a Commercial Single Voxel Technique at 1.5 and 3.0 T.

Area of Science:

• Magnetic Resonance Imaging
• Medical Physics
• Radiology

Background:

• Accurate liver fat quantification is crucial for diagnosing and monitoring metabolic diseases.
• The robustness of MRI techniques to variations in R2*, such as those caused by liver iron, is a key consideration for clinical application.
• The single-voxel high speed T2-corrected multi-echo (HISTO) technique's performance in the presence of R2* variations at 3.0 Tesla requires further evaluation.

Purpose of the Study:

• To evaluate the accuracy and robustness of the commercial HISTO technique for liver fat quantification at 3.0 T.
• To compare the HISTO technique with the Dixon technique across different magnetic field strengths (1.5 T and 3.0 T).
• To assess the impact of R2* variations on fat quantification accuracy in both phantom and patient studies.

Main Methods:

• Phantom studies with varying fat content and R2* were conducted at 1.5 T and 3.0 T.
• Data acquisition using HISTO and Dixon techniques in phantoms and 239 consecutive patients.
• Statistical analysis including Bland-Altman plots and one-sample t-tests to compare fat quantification accuracy and identify bias.

Main Results:

• HISTO demonstrated accuracy within 10% for R2* up to 100 s⁻¹ at both field strengths.
• Dixon technique maintained accuracy within 10% for higher R2* values (up to 350 s⁻¹ at 1.5 T, 550 s⁻¹ at 3.0 T).
• In patients with R2* < 100 s⁻¹, HISTO and Dixon agreed at 1.5 T but showed a significant bias at 3.0 T.

Conclusions:

• The HISTO technique is reliable for liver fat quantification when R2* is less than 100 s⁻¹, suitable for patients with mild liver iron overload.
• Caution is advised when using HISTO for fat quantification in cases with R2* exceeding 100 s⁻¹.
• The Dixon technique is recommended for hepatic fat quantification due to its superior robustness to R2* variations.