Fig. 1. Functional lung images in one animal. Images are contiguous tomographic sections viewed in the cranio-caudal direction and presented from top left to bottom right. The left side in the image corresponds to left side in the animal. Tracer activity is represented in a “hot” color scale (black = no activity; white = maximal activity) in that frame. (A ) Regional perfusion (Q̇r) before embolism. (B ) Q̇r after embolism. There is dramatic redistribution of Q̇r with many regions of the lungs essentially unperfused. (C ) Tracer activity remaining in the lungs at the end of the washout period after inhalational delivery of tracer. Note that higher activity corresponds to embolized areas, representing the slower washout rate of these regions.