Won Chulho, Chon Deokiee, Tajik Jehangir, Tran Binh Q, Robinswood G Blake, Beck Kenneth C, Hoffman Eric A
Department of Radiology, University of Iowa, Iowa City, Iowa 52241, USA.
J Appl Physiol (1985). 2003 Jun;94(6):2483-93. doi: 10.1152/japplphysiol.00688.2002. Epub 2003 Feb 14.
To determine regional pulmonary microvascular mean transit times (MTTs), we used electrocardiogram-gated X-ray computed tomographic imaging to follow bolus radiopaque contrast material through the lungs in anesthetized animals (7 dogs and 1 pig, prone and supine). By deconvolution/reconvolution of regional time-attenuation curves obtained from parenchyma and large lobar arteries, we estimated the microvascular residue function and reconstituted the regional microvascular time-attenuation curves and, thus, regional microvascular MTTs. The mean microvascular MTTs in the supine and prone postures were 3.94 +/- 1.0 and 3.40 +/- 0.84 (mean +/- SD), respectively. The dependent-nondependent vertical gradient of MTT was greater in the supine [slope = 0.25 +/- 0.10 (SD), P < 0.001 by t-test] than in the prone (-0.03 +/- 0.06 in 6 of 8 animals; 2 outliers had positive slopes) posture. In both postures, there was a trend toward faster transit times in the dorsal-basal lung region in six of the eight animals, suggesting gravity-independent higher vascular conductance dorsocaudally. We conclude that deconvolution methods, in association with electrocardiogram-gated high-speed X-ray computed tomography, can provide insights into regional heterogeneity of pulmonary microvascular MTT in vivo.
为了确定局部肺微血管平均通过时间（MTT），我们使用心电图门控X射线计算机断层成像技术，在麻醉动物（7只狗和1头猪，俯卧位和仰卧位）中追踪不透射线的造影剂团块在肺内的通过情况。通过对从实质和大叶动脉获得的局部时间-衰减曲线进行去卷积/再卷积，我们估计了微血管残留函数，并重建了局部微血管时间-衰减曲线，从而得到局部微血管MTT。仰卧位和俯卧位的平均微血管MTT分别为3.94±1.0和3.40±0.84（平均值±标准差）。MTT的依赖-非依赖垂直梯度在仰卧位时更大[斜率=0.25±0.10（标准差），t检验P<0.001]，而在俯卧位时（8只动物中有6只的斜率为-0.03±0.06；2只异常值的斜率为正值）较小。在两种体位下，8只动物中有6只在背侧基底肺区域存在通过时间更快的趋势，这表明背尾侧存在与重力无关的较高血管传导性。我们得出结论，去卷积方法与心电图门控高速X射线计算机断层成像相结合，能够深入了解体内肺微血管MTT的区域异质性。
