Simultaneous bilateral contrast injection in computed tomography pulmonary angiography

Abstract

Computed tomography pulmonary angiography (CTPA) has evolved as the gold standard for diagnosing pulmonary embolism. However, subsegmental arteries are often not assessed to do insufficient attenuation. To evaluate the influence of simultaneous bilateral versus unilateral injection of a fixed amount of contrast media on pulmonary artery opacification and image quality in CTPA. In this institutional review board-approved prospective study, 180 patients (91 women, mean age 61.9 ± 16.5 years) referred for CTPA (100 kV) due to suspected pulmonary embolism were randomized in groups of 45 patients each, with either unilateral (A:4 mL/s; B:6 mL/s) or bilateral (C: 6 mL/s; D: 8 mL/s) (Y-shaped line) injection of 50 mL contrast media. Attenuation was assessed including the subsegmental arteries (4th order). Image quality was evaluated by two readers in consensus using a three-point grading scale (3 = excellent image quality, no artifacts, 1 = non-diagnostic). Mean pulmonary artery attenuation was significantly higher with bilateral injection (1st to 3rd order: A: 303.6 ± 8.8HU; B: 371.1 ± 11.0HU vs. C: 443.2 ± 24.1HU; D: 562.3 ± 15.3HU, P < 0.001). Evaluation of subsegmental arteries was feasible for all patients in groups B-D, but only in 36/45 (80%) patients in group A. Subsegmental attenuation was significantly higher with bilateral injection (A: 284.7 ± 12.1HU; B: 367.4 ± 12.1HU vs. C: 494.2 ± 21.5HU; D: 562.3 ± 26.7HU, P < 0.001). Image quality was diagnostic for all patients but best for group C (A: 2.15 ± 0.4; B: 2.14 ± 0.5; C: 2.92 ± 0.3, and D: 2.51 ± 0.5). Using the same amount of contrast media, bilateral injection yields higher pulmonary artery attenuation and better image quality than unilateral injection. This technique may improve subsegmental pulmonary artery assessment.