Effect of B-value in revealing postinfarct myocardial microstructural remodeling using MR diffusion tensor imaging

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Cardiovascular Research

Background:

• Nonmonoexponential diffusion in biological tissues complicates Diffusion Tensor Imaging (DTI) quantification.
• DTI index accuracy is influenced by the diffusion sensitivity (b-value) used.
• Myocardial microstructural remodeling post-infarction requires precise imaging techniques.

Purpose of the Study:

• To investigate how varying b-values affect the detection of post-infarction myocardial microstructural remodeling using DTI.
• To determine optimal b-values for quantifying DTI indices in damaged heart tissue.
• To enhance the capability of conventional DTI in revealing myocardial degradation.

Main Methods:

• Ex vivo DTI scans of heart samples at 1, 3, 5, and 7 days post-infarction and controls.
• Acquisition of DTI data across a range of b-values (500–2500 s/mm²).
• Measurement of DTI indices (FA, mean, and directional diffusivities) in infarct, adjacent, and remote regions.

Main Results:

• DTI indices consistently decreased with increasing b-values across all regions and time points.
• Optimal b-values varied depending on the specific DTI index being measured.
• Fractional anisotropy (FA) showed highest sensitivity to fiber degradation at moderate b-values (1500–2000 s/mm²).
• Mean and directional diffusivities were most sensitive to alterations at lower b-values (≤1500 s/mm²) during necrotic and fibrotic phases.

Conclusions:

• The choice of b-value significantly impacts the sensitivity of DTI in assessing myocardial microstructural changes.
• Moderate b-values are optimal for evaluating fiber integrity (FA), while lower b-values are better for diffusivity changes.
• These findings support optimizing DTI protocols for improved assessment of cardiac microstructures in various pathological conditions.