Comparison of histologic and computed tomographic measurements of pig lung bronchi

Aim Light microscopy is used as template in the evaluation and further development of medical imaging methods. Tissue shrinkage caused by histological processing is known to influence lung tissue dimensions. In diagnostic of chronic obstructive pulmonary disease, computed tomography (CT) is widely used for automated airway measurement. We compared the bronchus wall thickness in histological and different image analysis methods.

Methods Airway measurements of pig lungs were performed after freezing under controlled inflation pressure in a liquid nitrogen bath. The wall thickness of seven bronchi was measured via MicroCT and CT using the integral based method (IBM) and the full-width-at-half-maximum method (FWHM) automatically and histologically on frozen and paraffin sections. Statistical analysis was performed using the Wilcoxon test, Pearson's correlation coefficient with a significance level at p<0.05, scatter plots and Bland Altman plots.

Results Bronchus wall thickness was smallest in frozen sections (median 0.71 mm) followed by paraffin sections (median 0.75 mm), MicroCT (median 0.84 mm) and CT measurements using IBM (median 0.68 mm) and FWHM (median 1.69 mm). Statistical significant differences were found among all tested groups (p<0.05) except for CT IBM and paraffin and frozen sections and MicroCT. High correlation was present between all parameters with statistical significance (p<0.05).

Conclusions Significant differences in airway measurement were found in the different analysing methods. The absolute measurements with CT IBM were closest to the histological results followed by MicroCT, whereas CT FWHM revealed a distinct divergence to the other groups.