³He lung morphometry technique: accuracy analysis and pulse sequence optimization.

Area of Science:

• Pulmonary Medicine
• Medical Imaging
• Biophysics

Background:

• The (3)He lung morphometry technique utilizes MRI to assess lung microstructure at the alveolar level.
• It enables 3D imaging of lung morphometry parameters like mean airspace chord length and surface-to-volume ratio from short MRI scans.
• Previously, these in vivo measurements were not feasible.

Purpose of the Study:

• To analyze the effects of realistic acinar airway structures on (3)He lung morphometry.
• To evaluate the impact of magnetic field inhomogeneities on parameter estimation.
• To derive optimal MR pulse sequence parameters for improved accuracy and reduced acquisition time.

Main Methods:

• Monte-Carlo computer simulations were employed to model realistic acinar airway structures, including branching and distributions of airway dimensions.
• The influence of susceptibility-induced magnetic field inhomogeneity was analyzed at different magnetic field strengths (B(0)).
• Theoretical derivation of optimal MR pulse sequence parameters, including specific b-values, was performed.

Main Results:

• The refined (3)He lung morphometry technique accurately measures geometrical and morphological parameters of acinar airways.
• The accuracy for determining the lung parenchyma surface-to-volume ratio was found to be within several percent.
• Magnetic field inhomogeneity effects were negligible at B(0) ≤ 3T but significant at higher fields.
• Optimal MR parameters were identified as three non-equidistant b-values: b(1)=0, b(2)≈2 s/cm(2), and b(3)≈8 s/cm(2).

Conclusions:

• The (3)He lung morphometry technique can be accurately applied to realistic lung acinar structures.
• The technique provides precise in vivo measurements of crucial lung morphometry parameters.
• Optimized MR pulse sequences enhance the efficiency and accuracy of this advanced lung imaging method.