Determination of optimized set of b-values for Apparent Diffusion Coefficient mapping in liver Diffusion-Weighted MRI

Area of Science:

• Medical Imaging
• Biophysics
• Signal Processing

Background:

• Diffusion-weighted MRI (DW-MRI) is crucial for assessing tissue microstructure.
• Accurate estimation of Apparent Diffusion Coefficient (ADC) maps is vital for clinical applications.
• Current DW-MRI protocols may not be optimized for noise performance, impacting ADC map precision.

Purpose of the Study:

• To derive the Cramér-Rao Lower Bound (CRLB) for monoexponential diffusion models.
• To develop a method for optimizing b-value selection to maximize ADC map noise performance.
• To validate the proposed CRLB-based optimization against experimental data.

Main Methods:

• CRLB derivation for monoexponential diffusion signal with realistic noise assumptions.
• Development of greedy and two-b-value search algorithms for optimized b-value set selection.
• Validation using synthetic data, phantoms, and in-vivo liver DW-MRI.

Main Results:

• CRLB-based optimized b-value sets demonstrated good agreement with experimental results.
• Optimized b-value sets significantly reduced ADC map variance compared to literature values for liver DWI.
• Higher b-values were found to be less critical for lower signal-to-noise ratios under Rician noise.

Conclusions:

• Optimizing b-value selection is critical for enhancing the precision of ADC maps in DW-MRI.
• The proposed CRLB-based approach offers a framework for optimizing and standardizing liver DWI acquisition parameters.
• This method can improve diagnostic accuracy by maximizing noise performance in ADC estimation.