Probing lung microstructure with hyperpolarized 3He gradient echo MRI.

Area of Science:

• Pulmonary Medicine
• Medical Imaging
• Biophysics

Background:

• Assessing lung microstructure non-invasively is crucial for understanding respiratory diseases.
• Current MRI techniques provide limited information on lung ventilation and vascular structure simultaneously.

Purpose of the Study:

• To demonstrate the capability of gradient echo MRI with hyperpolarized helium-3 ((3)He) gas for simultaneous in vivo assessment of lung ventilation, alveolar geometry, and blood vessel structure.
• To develop a theoretical model correlating MRI signal characteristics with lung microstructural parameters.

Main Methods:

• Utilized multi-gradient-echo (3)He MRI measurements in the lungs of healthy volunteers.
• Developed a theoretical model based on computer simulations of (3)He diffusion in an inhomogeneous magnetic field.
• Derived analytical expressions linking time-dependent MR signals to acinar airway and blood vessel network geometry.

Main Results:

• Successfully extracted in vivo data on lung ventilation, alveolar geometry, and blood vessel network structure simultaneously.
• Experimental data from eight healthy volunteers showed good agreement with existing literature values.
• The derived analytical expressions effectively related MR signal decay to lung microstructure.

Conclusions:

• Gradient echo MRI with hyperpolarized (3)He gas is a powerful tool for simultaneous in vivo lung microstructure assessment.
• This technique complements existing lung morphometry methods and offers new avenues for studying lung diseases.
• The approach provides complementary information to hyperpolarized (3)He diffusion MRI for comprehensive lung analysis.