ABSTRACT
Diffuse pulmonary diseases may be classified into two large groups of conditions: obstructive and restrictive diseases. This chapter presents an updated review of both clinical and technical aspects related to CAD and quantitative CT (QCT) in the evaluation of diffuse lung diseases, focusing on emphysema and other airway abnormalities, and fibrosing interstitial lung diseases (ILD). QCT has been mostly used to quantify the features of COPD, specifically emphysema, air trapping and bronchi abnormalities. For quantification of emphysema, the density mask technique is most widely used, with a threshold of -950 HU. CT parameters correlate well with airway obstruction, PFTs and other clinical aspects of the diseases. QCT of ILD has been used to classify the types of interstitial abnormalities, help the diagnostic process, determine the extent of disease, and detect subtle changes in volume, density and character of abnormalities in longitudinal evaluation of patients.
