Oligemia is considered to be present if, in a given lung region, the pulmonary vasculature is greatly diminished with concomitant hyperlucency of the lung parenchyma. Examples are given in the attached figures.
References
1.Westermark N. On roentgen diagnosis of lung embolism. Acta Radiol 1938; 19: 357-372.
2.Fleischner FG. Pulmonary embolism. Clin Radiol 1962; 13: 169-182.
