To improve the definition of the geometrical and mechanical properties of the porcine pulmonary arteries, we utilized an in vivo imaging-based approach to quantify the influence of static extravascular pressure change on pulmonary arterial geometry. The cross-sectional area and distance from the inlet of pulmonary arteries of two animals were measured over a range of static airway inflation pressure (7 cmH2O - 25 cmH2O, i.e. 0.69 kPa – 2.45 kPa). Vessels with diameter range of approximately 2.0 mm to 5.5 mm at airway inflation pressure of 25 cmH2O (2.45kPa) were considered. The results suggest that lung inflation stretches the vessels laterally, but has no statistically significant effect on diameter.