Optimization of tagged MRI for quantification of liver stiffness using computer simulated data

Area of Science:

• Medical Imaging
• Biophysics
• Hepatology

Background:

• Cardiac motion in the liver can indicate stiffness, aiding fibrosis staging.
• Tagged MRI is a promising technique for quantifying liver displacements.
• Optimizing acquisition protocols is essential for clinical application.

Purpose of the Study:

• To optimize tagged MRI acquisition for liver stiffness measurement.
• To evaluate the Harmonic Phase (HARP) method's performance with varying parameters.
• To assess the impact of noise on displacement estimation accuracy.

Main Methods:

• Reproduced a cardiac-induced liver strain study at 3T.
• Simulated tagged MR images with varied tag spacing and grid angles.
• Incorporated Partial Volume Effect (PVE), T1 relaxation, and noise levels.
• Calculated an Error Index (EI) to assess estimation accuracy.

Main Results:

• Decreased tag spacing improved displacement estimation accuracy without noise.
• Optimal accuracy was observed at a 0° grid angle, with minima at pixel size multiples.
• Increased noise levels degraded accuracy, diminishing the benefits of reduced tag spacing.
• Optimal tag spacing balances achievable resolution with noise robustness.

Conclusions:

• Protocol optimization is key for accurate cardiac-induced liver displacement measurement.
• The HARP method's accuracy is sensitive to tag spacing, grid angle, and noise.
• A compromise in tag spacing is needed for reliable liver stiffness quantification in clinical settings.