Clinical study of local pulmonary ventilation by nonradioactive xenon-enhanced computed tomography

The purpose of this study was to examine local pulmonary ventilation by analyzing inhaled non-radioactive xenon gas by computed tomography (CT). Preliminary experiments revealed that increase of the CT value was relatively low at the xenon gas concentration higher than 30% and that the basic CT value on the lung field increased as the concentration of inhaled oxygen increased. For clinical study, the subjects with diagnosed or suspected lung cancer inhaled a gas mixture of 30% xenon and 70% oxygen for 2 min. Scans were performed at four phases: before and immediately after inhalation, and during and after exhaustion of the gas mixture. At each phase, fixed 5-8 cross sections at pulmonary region were scanned. When the initial images were reproduced by both a microcomputer and an image processor for radionuclide medicine, pulmonary ventilation was plainly displayed, and not only the existence but also the direction of ventilation in bullae was also detectable. It was proved that inhalation of 30% xenon gas was sufficient to obtain excellent images. (author)