Basics and clinical application of nonradioactive xenon-enhanced

非放射性氙可用作评价肺通气的造影剂，因为肺的CT值与肺泡氙气浓度成比例增加。在这项研究中，提出了一种新的扫描和重建技术，详细映射肺通气与顺序获得氙增强CT。扫描，以测量氙气浓度进行前氙气吸入，结束时2分钟的20%氙气吸入，然后，1分钟后切换到室内空气中的气体。通过与呼吸同步进行扫描，以获得相同呼吸相位的图像。采用非线性几何变形技术对图像进行数字图像处理，以校正图像的小失配。使用指示剂稀释理论的原理分析肺中氙的动力学，以创建通气率常数图。在获得知情同意书后，使用上述技术对健康志愿者和肺气肿志愿者进行氙增强CT检查。肺气肿患者的平均通气速率常数明显低于健康志愿者。低通气率常数区与肺气肿区CT表现有较好的相关性。因此，结果表明，这种技术是有用的详细映射受损的通气。

Nonradioactive xenon can be used as a contrast medium for the evaluation of pulmonary ventilation because the CT number of the lung increases proportional to the alveolar xenon gas concentration. In this study, a new scan and reconstruction technique was proposed for detailed mapping of pulmonary ventilation with sequentially acquired xenon-enhanced CT.Scans to measure xenon concentration were performed before xenon inhalation, at the end of 2-min inhalation of 20-percent xenon, then, 1 min after switching the gas to room air. The scans were performed by synchronizing with respiration to obtain the images in the same respiration phase. Digital image processing with nonlinear geometrical warping technique was performed to correct the small mismatch of the images. The kinetics of xenon in the lung was analyzed using principles of indicator dilution theory to create a map of ventilation rate constant. After informed written consent was obtained, xenon-enhanced CT using the above-mentioned technique was applied to healthy volunteers and volunteers with pulmonary emphysema. The averaged ventilation rate constant in the patients with pulmonary emphysema was significantly lower than that in the healthy volunteers. The area with low ventilation rate constant was well correlated with the area of emphysema on CT image. Thus the results suggest that this technique is useful for detailed mapping of impaired ventilation.