Effect of site and rate of contrast material injection on pulmonary vascular distention

Rationale and Objectives. The authors performed this study to determine if there were differences in vascular caliber measured on angiograms obtained with the injection protocol used for spiral computed tomography (CT) versus that used for pulmonary angiography. Materials and Methods. The authors studied seven juvenile anesthetized pigs by using a prospective repeated measures experimental design. All pigs received injections of nonionic contrast material via catheters in the brachial vein, superior vena cava, main pulmonary artery, and left pulmonary artery. Weight-adjusted injection rates and volumes ranged from 0.05 mL/kg/sec (3.5 mL/sec, spiral CT protocol) to 0.56 mL/kg/sec (40 mL/sec, pulmonary angiography protocol). Heart rate and pulmonary artery and systemic artery pressures were recorded. During each injection, identically positioned pulmonary angiograms were obtained at full inspiration. Vessel diameters were measured at identical locations after each injection by two observers. The relationship between vessel diameter and hemodynamic parameters and injection site and rate was assessed with analysis of variance. Results. At suspended full inspiration, no statistically significant difference (P > .05) in vessel diameter or hemodynamic parameters was found between the different injection sites or rates. There was no difference in vascular caliber between systole and diastole. Conclusion. The improved detection of subsegmental pulmonary emboli at pulmonary angiography compared with contrast material-enhanced spiral CT is not due to differences in vascular distention