Objective: This study assesses if the arm of contrast infusion influences attenuation of the main pulmonary artery in computed tomography (CT) angiograms to evaluate for pulmonary emboli.
Methods: Four hundred seven consecutive CT angiograms performed to exclude pulmonary emboli were reviewed. Patient characteristics, study details, and interpretation results were collected. After exclusion criteria, 100 studies from each scanner (4, 16, and 64 slice) remained. A reader, blinded to injection side, measured the attenuation of the main pulmonary artery.
Results: The average attenuation in the main pulmonary artery was similar if infused through the right (275.4 HU) or left (275.0 HU) arm when controlling for confounders with a multiple regression analysis (P = 0.82). There was no statistical difference (P > 0.05) in the number of scans with attenuation less than 250 (45.9% right, 42.9% left), 200 (25.3% right, 29.2% left), or 150 HU (11.6% right, 12.3% left) and interpreted as indeterminate (1.4% right, 3.9% left) or nondiagnostic (2.7% right, 2.6% left).
Conclusions: Main pulmonary artery attenuation is independent of the arm of infusion when evaluating mean attenuation, attenuation beneath 250, 200, or 150 HU, or indeterminate or nondiagnostic interpretations for patients undergoing CT angiograms of the chest to rule out pulmonary emboli.