Flip Angle Optimisation for Quantitative Assessment of Pulmonary Ventilation and Perfusion at 3T

Motivation: The optimum flip angle which provides a trade-off between ventilation and perfusion signal in free-breathing proton MRI (3 T) of the lung is unknown. Goal(s): To optimise the acquisition of free-breathing pulmonary proton MRI to maximise both ventilation and perfusion signals. Approach: Assessment of the flip angle in a 2D fast field echo (FFE) sequence in healthy volunteers utilising voxel-wise lung ventilation (VOLVE) analysis. Results: Increasing the flip angle tends to reduce the ventilation signal but increase the perfusion signal. A flip angle higher than the Ernst angle for lung parenchyma is recommended when assessing both perfusion and ventilation. Impact: Demonstration of the dependence of 2D FFE proton MRI ventilation and perfusion signal on flip angle to inform future studies. A flip angle greater than the parenchyma Ernst angle maintains a strong ventilation signal without supressing the perfusion signal.