Spatially resolved measurements of hyperpolarized gas properties in the lung in vivo. Part I: Diffusion coefficient

In imaging of hyperpolarized noble gases, a knowledge of the diffusion coefficient (D) is important both as a contrast mechanism and in the design of pulse sequences. We have made diffusion coefficient maps of both hyperpolarized 3He and 129Xe in guinea pig lungs. Along the length of the trachea, 3He D values were on average 2.4 cm2/sec, closely reproducing calculated values for free gas (2.05 cm2/sec). The 3He D values measured perpendicular to the length of the trachea were approximately a factor of two less, indicating restriction to diffusion. Further evidence of restricted diffusion was seen in the distal pulmonary airspaces as the average 3He D was 0.16 cm2/sec. An additional cause for the smaller 3He D in the lung was due to the presence of air, which is composed of heavier and larger gases. The 129Xe results show similar trends, with the trachea D averaging 0.068 cm2/sec and the lung D averaging 0.021 cm2/sec. Magn Reson Med 42:721–728, 1999. © 1999 Wiley‐Liss, Inc.