Breathhold 19F-magnetic resonance imaging of lung ventilation using SF6 gas.

Objective: Development of a method to analyze lung ventilation by F-19-magnetic resonance imaging (MRI) of inspired SF, gas during breathhold. Material and Methods: Measurements were performed with a Siemens Magnetom Vision 1.5T scanner using the conventional gradient overdrive. Coronal images of the lung were acquired using ultrafast gradient-echo pulse sequences with TR/TE/alpha=1.4ms/ 0.48 ms/40 degrees without slice selection. With NEX = 200 averages and MA=32x64 raw data matrix, the acquisition time was 9 s/image. Higher spatial resolution of 4.7 x 6.3 x 15 mm(3) was obtained with a three-dimensional pulse sequence (TR/TE/ alpha=1.6ms/0.48ms/65 degrees, NEX=20) running for 49 s. Measurements wer performed in three anesthetized and ventilated pigs (18 kg). Results: A nearly linear relation between SF6 concentration and F-19 signal intensity was observed. The signal-to-noise ratio in images obtained without slice selection was 30.9, with slice selection it was 14.9. No differences between SF6 distribution to both lungs were observed in the animals. Conclusion: Breathhold MRI of SF6 gas distribution in the lung was demonstrated for the first time. The low spin-density was compensated for by highly repetitive signal averaging. Breathhold F-19-MR imaging of ventilated airspaces to assess SF6 distribution in the human lung appears to be an interesting new method, which can be implemented with little technical efforts, and does not rely on radioactive isotopes.