Correlation between High Resolution Computed Tomography and Tissue Morphometry of the Lung in Bleomycin-induced Pulmonary Fibrosis in the Rabbit

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Abstract
It is generally considered that the hazy increased density and consolidation seen on high resolution lung CT (HRCT) scans in patients with diffuse interstitial lung disease reflect tissue inflammation, whereas a predominance of linear structures corresponds to tissue fibrosis. The purpose of this study was to determine whether abnormalities observed by HRCT in the lungs of bleomycin-treated rabbits correlated with specific pathologic abnormalities seen on morphometric analysis of lung tissue. Bleomycin was instilled into the lungs of intubated rabbits and followed by inhalation of 100% oxygen. In different animals on Days 14, 28, or 56 after bleomycin, 1 or 1.5 mm HRCT scans were obtained at 8-mm intervals. Subsequently, the right lungs were processed for histology, and the left lungs were processed for determination of hydroxyproline content. Using a morphometric technique, the volume density of normal lung parenchyma, hazy increased density, consolidation, nodules, and central or peripheral lines was determined on each HRCT scan. After the rabbits were killed, the volume density of normal lung parenchyma, intra-alveolar cells, intra-alveolar amorphous material, and thickened interstitium (cellular or acellular) was also determined morphometrically in multiple lung tissue sections in each rabbit. There was a correlation between the volume densities of consolidation on HRCT scans and intra-alveolar cells and amorphous material on tissue morphometry (r = 0.90, p = 0.0001) over the 56-day period after bleomycin/oxygen administration. There was no correlation between the volume density of hazy increased lung density (HRCT) and the volume density of these same or any other individual or combined parameters (tissue morphometry) over the 56 days.(ABSTRACT TRUNCATED AT 250 WORDS)