Measurement of three-dimensional anatomy and function of pulmonary arteries with high-speed x-ray computed tomography.

Pulmonary arterial geometry was quantitatively evaluated in five dogs. One was a control dog, two were subjected to monocrotaline administration, and two had a subclavian-to-pulmonary artery shunt. Measurements of pulmonary arterial anatomy were made with the dynamic spatial reconstructor (DSR), a high-temporal-resolution, volumetric, roentgenographic, computed tomographic scanner. In the control dog, pulmonary arterial cross-sectional areas and segment lengths were measured both from images generated from DSR scans obtained during injection of contrast medium and from a methylmethacrylate cast of the same vascular tree. The correlations between the DSR and cast-based measurements of cross-sectional area and segment lengths were 0.98 and 0.97, respectively. Over periods of eight and 11 months' observation, the pulmonary arterial pressure in the two dogs with surgically created left-to-right shunts increased from 29/15 to 42/17 mm Hg and 19/12 to 25/16 mm Hg, respectively. The cross-sectional areas increased progressively in the proximal portion of the main lobar arteries, remained unchanged in the midportion, and decreased in the distal portion of these arteries. Similar changes occurred in one of the two dogs treated with monocrotaline injections, while in the other the taper of the distal vessels did not change significantly. Pulmonary vascular resistance, computed from cardiac output and pulmonary artery pressure, increased proportionately to the decrease of the cross-sectional areas of distal vessel in both the monocrotaline administration dogs; the resistance decreased proportionately to the increase of the pulmonary arterial cross-sectional areas in both of the surgical dogs.