Dynamic spiral MRI of pulmonary gas flow using hyperpolarized 3He: Preliminary studies in healthy and diseased lungs

An optimized interleaved-spiral pulse sequence, providing high spatial and temporal resolution, was developed for dynamic imaging of pulmonary ventilation with hyperpolarized (3)He, and tested in healthy volunteers and patients with lung disease. Off-resonance artifacts were minimized by using a short data-sampling period per interleaf, and gradient-fidelity errors were compensated for by using measured k-space trajectories for image reconstruction. A nonsequential acquisition order was implemented to improve image quality during periods of rapid signal change, such as early inspiration. Using a sliding-window reconstruction, cine-movies with a frame rate of 100 images per second were generated. Dynamic images demonstrating minimal susceptibility- and motion-induced artifacts were obtained in sagittal, coronal, and axial orientations. The pulse sequence had the flexibility to image multiple slices almost simultaneously. Our initial experience in healthy volunteers and subjects with lung pathology demonstrated the potential of this new tool for capturing the features of lung gas-flow dynamics.