Three-dimensional analysis of small airway with X-ray micro-CT

To identify the anatomy of small airways, we visualized and quantified the excised rat lung at varying lung volume using the microfocus X-ray CT. We insufflated tantalum dust as contrast agent. Lung volume was varied in steps from functional residual capacity (FRC: 2 mL) to the maximal lung capacity (MLC: 12 mL). At FRC we found out airway closure in small airways (Maximum lumen area was 0.06 mm² at MLC), where the bronchial walls are held in apposition. Lumen area dramatically varied at the first step during inflation and deflation, and the maximum area at MLC was 8 times as large as the minimum area at FRV.