Dephasing and diffusion on the alveolar surface

Area of Science:

• Medical Physics
• Pulmonary Imaging
• Biophysics

Background:

• Spin dephasing in lung tissue is crucial for magnetic resonance imaging (MRI) of pulmonary diseases.
• Accurate modeling of susceptibility and diffusion effects is needed for quantitative analysis.

Purpose of the Study:

• To develop a closed-form surface model for spin dephasing on the alveolar surface.
• To validate the model against numerical simulations and in vivo measurements.
• To enable quantification of the local mean alveolar radius.

Main Methods:

• Developed a surface model incorporating susceptibility and diffusion effects.
• Solved the Bloch-Torrey equation on the alveolar surface.
• Validated against synchrotron-based μCT data of mouse lung tissue and Wigner-Seitz model simulations.
• Compared model predictions with in vivo lung MRI measurements at 1.5 Tesla.

Main Results:

• The model provides a closed-form solution for spin dephasing.
• Nonlocal susceptibility effects were validated through simulations.
• Free induction decay measurements correlate well with microscopic tissue parameters.
• The model successfully quantifies the local mean alveolar radius.

Conclusions:

• The proposed surface model accurately describes spin dephasing in lung tissue.
• The model allows for in vivo quantification of the mean alveolar radius.
• This approach has potential applications in the clinical diagnosis and therapy of pulmonary diseases.