Factor analysis of 81mKr lung ventilation studies.

Factor analysis of dynamic structures (FADS) summarizes data depending on time and space in a few elementary components. Each of them associates a time-activity curve (factor) and the spatial distribution of the corresponding events. The aim was to evaluate the patterns, the number of components, and their possible link to physiology when FADS was applied to scintigraphic images representing a composite of a 81mKr ventilation cycle. In a study of 26 patients (10 normal, 16 pathologic), components were found that represent: (1) a rapid and steeply changing ventilation factor, corresponding mainly to bases in normal subjects and whole lung fields in patients, (2) a slower expiration and shorter inspiration ventilation factor distributed throughout both lung fields in all patients, (3) a constant activity curve, with an inspiratory activity peak distributed over both lung fields and the large airways, and (4) a factor including a phase shift with respect to the first; this was found significantly more often in patients with pathology.