Comparison of gadolinium-enhanced and ferumoxytol-enhanced conventional and UTE-MRA for the depiction of the pulmonary vasculature.

Purpose: To evaluate the feasibility of ferumoxytol (FE)-enhanced UTE-MRA for depiction of the pulmonary vascular and nonvascular structures.
Methods: Twenty healthy volunteers underwent contrast-enhanced pulmonary MRA at 3 T during 2 visits, separated by at least 4 weeks. Visit 1: The MRA started with a conventional multiphase 3D T ₁ -weighted breath-held spoiled gradient-echo MRA before and after the injection of 0.1 mmol/kg gadobenate dimeglumine (GD). Subsequently, free-breathing GD-UTE-MRA was acquired as a series of 3 flip angles (FAs) (6°, 12°, 18°) to optimize T ₁ weighting. Visit 2: After the injection of 4 mg/kg FE, MRA was performed during the steady state, starting with a conventional 3D T ₁ -weighted breath-held spoiled gradient-echo MRA and followed by free-breathing FE-UTE-MRA, both at 4 different FAs (6°, 12°, 18°, 24°). The optimal FA for best T ₁ contrast was evaluated. Image quality at the optimal FA was compared between methods on a 4-point ordinal scale, using multiphase GD conventional pulmonary MRA (cMRA) as standard of reference.
Results: Flip angle in the range of 18°-24° resulted in best T ₁ contrast for FE cMRA and both UTE-MRA techniques (p > .05). At optimized FA, image quality of the vasculature was good/excellent with both FE-UTE-MRA and GD cMRA (98% versus 97%; p = .51). Both UTE techniques provided superior depiction of nonvascular structures compared with either GD-enhanced or FE-enhanced cMRA (p < .001). However, GD-UTE-MRA showed the lowest image quality of the angiogram due to low image contrast.
Conclusion: Free-breathing UTE-MRA using FE is feasible for simultaneous assessment of the pulmonary vasculature and nonvascular structures. Patient studies should investigate the clinical utility of free-breathing UTE-MRA for assessment of pulmonary emboli.
(© 2019 International Society for Magnetic Resonance in Medicine.)