Tajik Jehangir K, Chon Deokiee, Won Chulho, Tran Binh Q, Hoffman Eric A
Department of Physiology, University of Iowa College of Medicine, Iowa City 52242, USA.
Acad Radiol. 2002 Feb;9(2):130-46. doi: 10.1016/s1076-6332(03)80163-0.
To evaluate the adequacy of multibreath and single-breath stable xenon gas techniques to measure regional ventilation during cardiac-gated, high-speed, multisection imaging, the authors carried out a series of studies using electron-beam computed tomography (CT) and a recently introduced subsecond multisection spiral CT scanner.
In four anesthetized pigs, the authors implemented single-breath and/or dynamic multibreath wash-in and washout protocols with respiratory-- and cardiac-gated image acquisition. The effects of varying tidal volume and inspiratory flow rate were evaluated independently. Scanning was done at end expiration to avoid artifacts from partial volumed conducting airways, which are filled with inspired gas concentration during inspiration.
A single breath of 100% xenon provides adequate enhancement in the lung parenchyma (mean, 32 HU +/- 1.85 [standard error]) and should not cause unwanted side effects (mean xenon concentration in lung periphery, 21%). The single-breath method is suitable for studies requiring only short periods of apnea. Using the multibreath method, in dependent portions of the lung, there was close agreement between measured changes and predictions based on the xenon calibration data. More than 10 breaths were needed to clear tracer from poorly ventilated areas, and some nondependent regions demonstrated apparently "linear" rather than exponential clearance curves, possibly reflecting longer washout times. Analysis of wash-in and washout curves revealed vertical ventilation gradients and, at higher inspiratory flow rates, redistribution of ventilation to areas of the lung with greater pathway conductance.
With careful attention to lung volume and use of cardiac gating, it is now possible to correlate lung structure with function to a degree heretofore not possible.
为了评估多呼吸和单呼吸稳定氙气技术在心脏门控、高速、多层面成像过程中测量局部通气的适用性，作者使用电子束计算机断层扫描（CT）和最近推出的亚秒级多层面螺旋CT扫描仪进行了一系列研究。
在4只麻醉猪中，作者实施了单呼吸和/或动态多呼吸的氙气吸入和呼出方案，并进行呼吸和心脏门控图像采集。分别评估了潮气量和吸气流量变化的影响。在呼气末进行扫描，以避免部分容积传导气道产生的伪影，这些气道在吸气时充满吸入气体浓度。
单次呼吸100%氙气可使肺实质获得足够的强化（平均值为32HU±1.85[标准误差]），且不应引起不良副作用（肺周边平均氙气浓度为21%）。单呼吸方法适用于仅需要短时间屏气的研究。使用多呼吸方法时，在肺的非依赖部分，测量变化与基于氙气校准数据的预测之间有密切一致性。需要超过10次呼吸才能清除通气不良区域的示踪剂，一些非依赖区域显示出明显的“线性”而非指数清除曲线，这可能反映了更长的呼出时间。对吸入和呼出曲线的分析揭示了垂直通气梯度，并且在较高吸气流量时，通气重新分布到肺中传导路径更大的区域。
通过仔细关注肺容积并使用心脏门控，现在有可能在一定程度上使肺结构与功能相关联，这在以前是不可能的。
