Relative enhanced diffusivity: noise sensitivity, protocol optimization, and the relation to intravoxel incoherent...

Area of Science:

• Medical imaging
• Diffusion-weighted MRI
• Quantitative imaging

Background:

• Intravoxel incoherent motion (IVIM) imaging provides insights into tissue microstructural and microcirculatory properties.
• Relative enhanced diffusivity (RED) is a derived parameter potentially offering complementary information to IVIM.
• Understanding the relationship between RED and IVIM is crucial for accurate interpretation and application in clinical settings.

Purpose of the Study:

• To mathematically derive the relationship between RED and IVIM parameters.
• To investigate the influence of image noise and intermediate b-value selection on RED.
• To optimize RED parameter estimation for breast and liver imaging.

Main Methods:

• Mathematical derivation to express RED in terms of IVIM parameters (f, D, D*).
• Monte Carlo simulations to generate diffusion-weighted imaging data for breast and liver tissues.
• Analysis of noise impact and b-value optimization across varying signal-to-noise ratios (SNRs).

Main Results:

• RED demonstrates an approximate linear relationship with the IVIM parameter f and inverse proportionality with D.
• RED exhibits an inverse exponential decay with respect to the IVIM parameter D*.
• The selection of intermediate b-values significantly impacts RED's noise robustness and discriminatory power, with optimal values identified for breast (100 s/mm²) and liver (50 s/mm²).
• RED is effectively a reparameterization of IVIM estimates using three b-values.

Conclusions:

• RED imaging in breast and liver tissues benefits from specific intermediate b-values (100 s/mm² for breast, 50 s/mm² for liver).
• Future RED studies should incorporate estimation of IVIM parameters (f and D) using three b-values for comparative analysis.
• RED offers a potentially valuable quantitative imaging biomarker when optimized with appropriate b-value selection.