Thin-Section CT Features of Idiopathic Pulmonary Fibrosis Correlated with Micro-CT and Histologic Analysis

Abstract

Purpose To elucidate the underlying lung changes responsible for the computed tomographic (CT) features of idiopathic pulmonary fibrosis (IPF) and to gain insight into the way IPF proceeds through the lungs and progresses over time. Materials and Methods Micro-CT studies of tissue cores obtained from explant lungs were examined and were correlated 1:1 with a CT study obtained immediately before transplantation. Samples for histologic analysis were obtained from selected cores. Results In areas with no or minimal abnormalities on CT images, small areas of increased attenuation located in or near the interlobular septa can be seen on micro-CT studies. In more involved lung areas, the number of opacities increases and opacities enlarge and approach each other along the interlobular septa, causing a fine reticular pattern on CT images. Simultaneously, air-containing structures in and around these opacities arise, corresponding with small cysts on CT images. Honeycombing is caused by a progressive increase in the number and size of these cystic structures and tissue opacities that gradually extend toward the centrilobular region and finally replace the entire lobule. At histologic analysis, the small islands of increased attenuation very likely correspond with fibroblastic foci. Near these fibroblastic foci, an abnormal adjacency of alveolar walls was seen, suggesting alveolar collapse. In later stages, normal lung tissue is replaced by a large amount of young collagen, as seen in patients with advanced fibrosis. Conclusion Fibrosis and cyst formation in patients with IPF seem to start at the periphery of the pulmonary lobule and progressively extend toward the core of this anatomic lung unit. Evidence was found that alveolar collapse might already be present in an early stage when there is only little pulmonary fibrosis. RSNA, 2016.

Increased Expiratory Computed Tomography Density Reveals Possible Abnormalities in Radiologically Preserved Lung Parenchyma in Idiopathic Pulmonary Fibrosis

“…Recently, Mai et al 29 reported that even in areas with no or minimal abnormalities on CT images, there were islands of increased attenuation located in or near the interlobular septa on micro-CT scans. These areas corresponded to fibroblastic foci (ie, active, very recently formed fibrotic areas) at histologic analysis.…”

Does the computed tomographic appearance of the lung differ between young and old dogs?

“…The main limitation of the present study was the lack of pathologic examination of lungs, which prevents histologic proof of the nature of lesions identified by CT, and allows the possibility that there were age‐related lung changes that were undetected by CT. All CT studies reviewed in this study were obtained using settings suitable for clinical assessment of the lung of dogs, but more detailed assessment is possible using thinner (1 mm) CT slices or micro‐CT with histologic examination of precisely orientated lung sections. Further studies are indicated to better examine imaging–pathologic correlations in the aging canine lung.…”

Surfactant replacement therapy reduces acute lung injury and collapse induration-related lung remodeling in the bleomycin model

“…Coxson and coworkers performed a quantitative morphological study in IPF lungs and observed that the main consequence of IPF on lung structure is a dramatic decline in surface area of the alveolar epithelium (12) so that it has been discussed very comprehensively that alveolar collapse and collapse induration are extremely important pathological events in fibrosing lung diseases (35,46,67). Also, micro-CT studies from human IPF suggest that alveolar collapse takes place at a very early stage of the disease in the absence of severe fibrotic remodeling so that it obviously predates collagen deposition in IPF (41). Structure-function relationships in the bleomycin model of lung injury and fibrosis showed that the number of open alveoli per lung was highly correlated with lung mechanical impairment (39).…”