Airway dimensions measured from micro-computed tomography and high-resolution computed tomography

Area of Science:

• Pulmonary imaging and respiratory system research.

Background:

• High-resolution computed tomography (HRCT) measurements of airway dimensions are subject to volume averaging errors, leading to over- and underestimation.
• Accurate airway dimension measurement is crucial for diagnosing and monitoring respiratory diseases.

Purpose of the Study:

• To calibrate computerized airway dimension measurements obtained from HRCT using a novel, high-resolution 3D micro-computed tomography (CT) standard and traditional morphometry.
• To establish accurate measurement algorithms for airway lumen area (Ai), wall area (A(aw)), and lumen volume (Vi) using HRCT.

Main Methods:

• Inflation-fixed porcine lung cubes were scanned using both HRCT and micro-CT.
• Airway dimensions (Ai, A(aw), Vi) were measured and compared between HRCT, micro-CT, and traditional morphometry.
• A calibration algorithm for HRCT measurements was developed based on the micro-CT standard.

Main Results:

• HRCT measurements showed systematic, size-dependent underestimation of Ai and overestimation of A(aw).
• After calibration, HRCT measurements achieved 95% limits of agreement of +/-3.2 mm² for Ai, +/-4.3 mm² for A(aw), and +/-11.2 mm³ for Vi, with no systematic error.
• Morphometric measurements agreed with micro-CT with no systematic error (+/-2.5 mm²).

Conclusions:

• Micro-CT provides a reliable 3D calibration standard for HRCT-based airway lumen volume measurements.
• Traditional morphometry is suitable for calibrating 2D measurements of airway lumen area.
• The developed image dataset can validate future 3D segmentation algorithms for airway analysis.