Regional Quantification of Bleomycin-Induced Pulmonary Fibrosis in Mice by Microcomputed Tomography for the Assessment of the Therapeutic Responses of Antifibrotic Drugs

Abstract

Idiopathic pulmonary fibrosis is a serious, progressive, and fatal lung disorder. Microcomputed tomography (micro-CT) is a powerful technology for drug development that can be used to monitor the progression of lung fibrosis in animal model. However, the current analysis methods for quantifying micro-CT image require time and experiences to analyze CT data in detail by radiologists. Here, a self-controlled extracted subvolume histogram analysis (SEHA) method was developed to assess the development of pulmonary fibrosis easily.Method: The SEHA method consisted of five steps: in vivo micro-CT imaging with fixed posture, image reconstruction, subvolume extraction, histogram analysis, and scan comparison before or after treatment. The robustness, repeatability, and accuracy of SEHA were validated.Results: The sites of fibrosis in 66 bleomycin (BLM)-induced pulmonary fibrosis mice were variable but generally occurred in the middle and upper lungs. In validation of the accuracy and robustness of SEHA, the percentage of high-density voxels in selected volumes of interest (VOIs) was well correlated with that from whole-lung analysis both at Day 7 and Day 21 after bleomycin administration (R2= 0.8784 and 0.8464, respectively; P<0.0001). In validation of the repeatability of SEHA, the relative standard deviation (RSD) of the percentage of high-density voxels in the VOIs was significantly less than that of whole-lung analysis (1.645±1.884% VS 3.501±1.637%, P=0.0282). In validation of the radiographic and histological accuracy of SEHA, there was a good correlation between micro-CT and histological analysis both in the early and late stages of fibrosis (R2= 0.7434 and 0.7573, respectively; P<0.0001).Conclusion: SEHA is a straight forward method for quantifying pulmonary fibrosis and facilitate for primary micro-CT data analyzer.