Basics and clinical application of nonradioactive xenon-enhanced

非放射性氙气可作为评价肺通气的造影剂，因为肺的CT数与肺泡氙气浓度成正比增加。在这项研究中，提出了一种新的扫描和重建技术，用于用顺序获得的氙增强CT详细绘制肺通气。在吸入氙气前，在吸入20%氙气2分钟后，然后在将气体切换到室内空气1分钟后，进行扫描以测量氙气浓度。扫描与呼吸同步进行，以获得同一呼吸阶段的图像。采用非线性几何翘曲技术对图像进行数字处理，以纠正图像的小错配。利用指标稀释理论的原理分析了氙在肺中的动力学，并绘制了通气速率常数图。在获得知情书面同意后，使用上述技术的氙增强CT应用于健康志愿者和肺气肿志愿者。肺气肿患者的平均通气速率常数明显低于健康志愿者。在CT图像上，通气率常数低的区域与肺气肿区域具有良好的相关性。因此，结果表明，该技术是有用的详细绘制受损通风。

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.