Flip angle considerations in (3)Helium-MRI

(3)Helium-MRT (He-3-MRT) can be used for analysis of lung function, e.g. dy namic imaging of ventilation and gas diffusion within the lung, assessment of intrapulmonary oxygen concentrations and their time course. During imagi ng, the irreversible signal loss due to depolarizing radio frequency excita tions can be described using the flip angle (FA)alpha. This parameter has t o be quantified in order to account for it during quantitative assessment o f the (3)helium signal intensity and its temporal development. This technic al report reviews two different methods to determine alpha. Limitations and possible error sources of each method are discussed. Copyright (C) 2000 Jo hn Wiley & Sons, Ltd.