Biplane videoroentgenographic analysis of dynamic regional lung strains in dogs

A method is described for determining the spatial distribution of pulmonary parenchymal strains in the intact canine thorax, using measurements of displacement of metallic (1-mm-diam)) markers percutaneously implanted throughout the parenchyma of the right lung. Dogs are supported head up or head down in a water-immersion respirator with the animal's airway connected to ambient air. Tracking of the parenchymal markers is accomplished by stereo biplane videoroentgenographic recordings, which allow high temporal (60/S) and spatial (+/- 1.5 mm) resolution measurements of the "tagged" lungs during various respiratory maneuvers. After transferring the video information to a stop-action video disc, an operator-interactive computer program is used to input the geometric coordinates of the markers into the computer. The true spatial coordinates are then determined after correction for pincushion and magnification distortions. Spatial and temporal distributions of regional parenchymal strains are obtained by determining the distance between markers on a frame-by-frame basis over the extent of the respiratory cycle. Data indicate nonuniformity in regional lung parenchymal strains.