Can dynamic krypton-81m imaging separate regional ventilation and volume?

This study explores the assumption that 81mKr static images represent regional ventilation. Dynamic acquisition of 81mKr ventilation images permits creation of time-activity curves and the possible separation of the confounding influences of ventilation and volume. By using a two-compartment gas mixing lung phantom, the results demonstrate that both total and tidal 81mKr are closely related to regional ventilation. In 61 children and 15 adult volunteers, there was good agreement between fractional ventilation assessed by total and tidal 81mKr. The dynamic steady-state ventilation image can be analyzed to separate tidally exchanged and resident 81mKr. This may allow regional ventilation to be distinguished from regional volume.