Connecting macroscopic diffusion metrics of cardiac diffusion tensor imaging and microscopic myocardial structures...

Area of Science:

• Cardiovascular Imaging
• Biophysics
• Medical Physics

Background:

• Diffusion Tensor Imaging (DTI) provides macroscopic insights into tissue microstructure.
• Understanding the relationship between microscopic cardiac structures and DTI metrics is crucial for accurate diagnosis and treatment.
• Current methods lack detailed microstructural modeling for whole-heart DTI simulations.

Purpose of the Study:

• To develop and validate a cardiac DTI simulation method integrating microscopic details of the myocardium.
• To investigate the impact of extracellular volume, myocyte orientation heterogeneity, and myocyte size on DTI metrics.
• To establish a link between polarized light imaging (PLI) data and DTI simulations for whole-heart analysis.

Main Methods:

• Proposed a cardiac DTI simulation using Bloch equations and Monte Carlo random walks.
• Reconstructed a realistic myocardium model from human heart PLI data.
• Iteratively determined microstructure parameters by matching simulation and real DTI acquisitions (helix angle, FA, MD).

Main Results:

• Demonstrated the feasibility of whole-heart DTI simulation using PLI measurements.
• Increased extracellular volume (15% to 55%) significantly decreased fractional anisotropy (FA) and increased axial/radial diffusivities.
• Varied myocyte orientation heterogeneity and size showed significant impacts on FA and diffusivity metrics.

Conclusions:

• The developed cardiac DTI simulation method is feasible and accurate for whole-heart analysis.
• Microscopic structural changes, including extracellular volume and myocyte characteristics, directly influence macroscopic DTI measurements.
• This approach offers a powerful tool for understanding cardiac microstructure and its relation to DTI in health and disease.