Local pulmonary ventilation using nonradioactive xenon-enhanced ultrafast computed tomography.

Using ultrafast computed tomography, we have developed a technique for measuring local ventilation in a volume of 1 cm3 in the normal supine lung. The technique employs the inert gas xenon in its nonradioactive form and makes use of its radiopaque properties. The inhalation of xenon results in changes in density which can be detected and measured in Hounsfield units using ultrafast computed tomography. Using this property and assuming a monoexponential form for the washin curve of the inert gas, it is possible to calculate ventilation at a local level. The methodology also permits measurements of minute ventilation during the procedure, thus permitting standardization. Using this technique, we calculated local ventilation in six normal subjects and have demonstrated a minor gradient in ventilation between the dorsal and ventral regions of the lung while in the supine position.