Thin-Section CT Features of Idiopathic Pulmonary Fibrosis Correlated with Micro-CT and Histologic Analysis.
Radiology. 2017 Apr;283(1):252-263. doi: 10.1148/radiol.2016152362. Epub 2016 Oct 6.
Mai C1, Verleden SE1, McDonough JE1, Willems S1, De Wever W1, Coolen J1, Dubbeldam A1, Van Raemdonck DE1, Verbeken EK1, Verleden GM1, Hogg JC1, Vanaudenaerde BM1, Wuyts WA1, Verschakelen JA1.
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.