MR tagging of human lungs using hyperpolarized ³He gas

Purpose: To evaluate the use of spin-tagging in conjunction with hyperpolarized gas imaging for monitoring lung ventilation and gas diffusion. Methods and Materials: Images were taken at 0.15 T using single shot RARE, with hyperpolarized ³He gas prepared by the metastability exchange technique. Sinusoidal modulation of the longitudinal magnetization (tag) was produced by two 90-degree rf pulses separated by a gradient pulse. The diffusion of ³He gas in the lungs was measured by monitoring the decay of the tags. This study was conducted on a 25-year-old, male, healthy volunteer. Results: Clear tags in hyperpolarized ³He gas both in vivo and in vitro were generated. The relative movement of the lung compared to a static, partial breath-hold was measured following inspiration or expiration. The diffusion coefficient of ³He in the lungs was found to be 0.02 ± 0.005 cm²seconds^-1. Conclusion: The spin-tagging of hyperpolarized ³He in the lungs is possible, and allows regional lung movements to be measured following inspiration and expiration. It also allows quantification of the diffusion of the ³He gas.