Dynamic 19 F‐MRI of pulmonary ventilation using sulfur hexafluoride (SF 6 ) gas

A new method for dynamic imaging of pulmonary wash‐in and wash‐out kinetics of inhaled sulfur hexafluoride (SF 6 ) gas was developed. Measurements at the fluorine‐19 Larmor frequency were performed in pigs using a gradient echo pulse sequence with 0.5 ms echo time and a measurement time of 9.1 s per image. Dynamic MRI was performed during wash‐in and wash‐out of SF 6 gas in mechanically ventilated porcine lungs. A postprocessing strategy was developed for quantitative determination of wash‐out time constants in the presence of noise. Mean wash‐out constants were 4.78 ± 0.48 breaths vs. 4.33 ± 0.76 breaths for left and right lung when ventilation was performed with low tidal volume, and 1.73 ± 0.16 breaths vs. 1.85 ± 0.11 breaths with high tidal volume ventilation. In conclusion, breath‐hold MRI of SF 6 gas is feasible in large animals. Moreover, regional wash‐in and wash‐out kinetics of SF 6 can be determined noninvasively with this new method. Potential human applications are discussed. Magn Reson Med 45:605–613, 2001. © 2001 Wiley‐Liss, Inc.