CT-based assessment of alveolar collapse using attenuation histograms in inspiration and expiration: Evaluation as a prognostic imaging marker in IPF patients

To determine whether alveolar collapse, defined as an abnormal increase in CT attenuation during expiration, can be detected using paired attenuation histograms in inspiration and expiration and used as a potential predictive marker in IPF patients.   Methods Sixty-six individuals with IPF obtained CT scans during inspiration and expiration. Density histograms were created and analyzed. After each respective 3-year observation period, the patient population was split into two subgroups according to their status (endpoints: death/transplantation vs still under clinical surveillance). An independent t-test was used to compare the CT-derived histogram parameters of attenuation between the two subgroups (ratio of mean attenuation in expiration/inspiration (meanHUratio) and SD, skewness and kurtosis in expiration). Results After the individual observation period of 3 years, 37 patients were still under clinical surveillance while 29 had died or received a transplantation. All baseline characteristics (meanHUratio and SD, skewness and kurtosis of expiratory attenuation histograms) were significantly different between the subgroups (p = 0.004, p = 0.009, p < 0.001 and p < 0.001, respectively).   Conclusion Expiratory attenuation histogram analysis can be used to demonstrate the concept of alveolar collapse as a potential prognostic marker in IPF patients.