Physiologic imaging of the lung with volumetric high-resolution CT

The combination of high-resolution computed tomography (HRCT), rapid volumetric scanning, and advanced image display and analysis applications software is a powerful potential tool for the evaluation of physiologic and pharmacologic events in the lung. Currently employed in the experimental setting, this tool can provide verifiable and quantifiable information about regional responses in the lung, which were previously impossible to demonstrate. This is particularly true when physiologic or pharmacologic effects result in an anatomic change that can be directly imaged and measured within the limits of CT resolution. However, information about events occurring beyond resolution limits is potentially available indirectly from lung density and pulmonary blood flow measurements using CT techniques. The results of animal airway reactivity experiments making use of i.v. methacholine and CT imaging tools are presented as an example of "physiologic imaging."