Lam Wilfred W, Holdsworth David W, Du Louise Y, Drangova Maria, McCormack David G, Santyr Giles E
Imaging Research Laboratories, Robarts Research Institute, P.O. Box 5015, 100 Perth Drive, London, Ontario N6A 5K8, Canada.
J Appl Physiol (1985). 2007 Nov;103(5):1848-56. doi: 10.1152/japplphysiol.00009.2007. Epub 2007 Aug 9.
We measured ventilation (V) in seven anesthetized, mechanically ventilated, supine Wistar rats. Images of the whole lung were continuously acquired using a dynamic, flat-panel volumetric micro-computed tomography (micro-CT) scanner during ventilation with a xenon/oxygen (Xe-O(2)) gas mixture. Forty time-resolved volumes consisting of eighty 0.45-mm-thick slices (covering the entire lung) were acquired in 40 s, using a gantry rotation rate of one rotation per second. The animals were ventilated at a respiratory rate of 60 breaths/min, matching the gantry rotation rate, and imaged without suspending ventilation. A previously published theoretical model was modified slightly and used to calculate the whole lung ventilation from volumes of interest generated by seeded region growing. Linear regression of calculated whole lung ventilation volumes vs. expected tidal volumes yielded a slope of 1.12 +/- 0.11 (slope +/- SE) and a y-intercept of -1.56 +/- 0.42 ml (y-intercept +/- SE) with 95% confidence intervals of 0.83 to 1.40 and -2.6 to -0.5 ml, respectively. The same model was used to calculate the regional ventilation in axial slices for each animal. Voxels were fit to the model to yield a map of V, which displayed an anterior/posterior gravitational gradient of (-3.9 +/- 1.8) x 10(-6) mlxs(-1)xcm(-1) for slices immediately superior to the diaphragm and (-6.0 +/- 2.4) x 10(-6) mlxs(-1)xcm(-1) for slices at the midlevel of the heart (mean +/- SD). Thus continuous Xe-enhanced computed tomography enables the noninvasive determination of regional V with the temporal and spatial resolution necessary for rats.
我们对7只麻醉、机械通气、仰卧位的Wistar大鼠测量了通气量（V）。在使用氙气/氧气（Xe - O₂）混合气体通气期间，使用动态平板容积微型计算机断层扫描（微型CT）扫描仪连续采集全肺图像。每秒进行一次机架旋转，在40秒内采集了由80个0.45毫米厚切片（覆盖整个肺部）组成的40个时间分辨容积。动物以60次/分钟的呼吸频率通气，与机架旋转速率匹配，且在不暂停通气的情况下成像。对先前发表的理论模型稍作修改，用于根据种子区域生长生成的感兴趣容积计算全肺通气量。计算得到的全肺通气量与预期潮气量的线性回归斜率为1.12±0.11（斜率±标准误），y轴截距为 - 1.56±0.42毫升（y轴截距±标准误），95%置信区间分别为0.83至1.40和 - 2.6至 - 0.5毫升。使用相同模型计算每只动物轴向切片的区域通气量。将体素拟合到模型以生成V图，对于紧邻膈肌上方的切片，V显示出前后重力梯度为（-3.9±1.8）×10⁻⁶毫升·秒⁻¹·厘米⁻¹，对于心脏中部水平的切片为（-6.0±2.4）×10⁻⁶毫升·秒⁻¹·厘米⁻¹（平均值±标准差）。因此，连续Xe增强计算机断层扫描能够以大鼠所需的时间和空间分辨率无创测定区域V。
