Optimized acquisition for simultaneous intravoxel incoherent motion and R₂ quantification in the liver

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Biophysics
• Medical Imaging

Background:

• Intravoxel incoherent motion (IVIM) MRI quantifies microvascular blood flow and diffusion.
• R2 quantification measures liver tissue relaxation properties.
• Simultaneous IVIM and R2 quantification can provide comprehensive liver tissue characterization.

Purpose of the Study:

• To design optimized b-value, first-order motion moment (M1), and echo time (TE) acquisition parameters for simultaneous IVIM and R2 quantification in the liver.
• To evaluate the test-retest repeatability and interlobar agreement of the optimized acquisitions.

Main Methods:

• Developed b-M1-optimized (single TE) and b-M1-TE-optimized (multi-TE) IVIM acquisition protocols using Cramer-Rao lower-bound optimization.
• Acquired data in 11 healthy volunteers, repeating each optimized acquisition for test-retest analysis.
• Estimated IVIM parameters (D, f1, f2, Vb1, Vb2) and R2 parameters (R2t, R2b) and applied six R2-correction methods.

Main Results:

• The b-M1-TE-optimized acquisition showed acceptable to excellent repeatability for most IVIM and R2 parameters in the right liver lobe.
• Good interlobar agreement was observed for D, Vb1, Vb2, R2t, and R2b, with exceptions for f1 and f2.
• R2 correction of f estimates using fixed R2t and R2b values in the single-TE acquisition yielded similar results to the multi-TE approach.

Conclusions:

• The b-M1-TE-optimized IVIM acquisition enables simultaneous and repeatable IVIM and R2 quantification in the liver.
• For single-TE IVIM data, using fixed R2t and R2b values for R2 correction of f estimates may be acceptable.