Hakim T S, Lisbona R, Dean G W
Department of Physiology, Royal Victoria Hospital, McGill University, Montreal, Quebec, Canada.
J Appl Physiol (1985). 1987 Sep;63(3):1114-21. doi: 10.1152/jappl.1987.63.3.1114.
Single-photon emission computerized tomography of the lung with 99mTc-labeled human albumin macroaggregates (99mTc-MAA) was used in six healthy subjects to study the three-dimensional distribution of pulmonary blood flow. 99mTc-MAA was injected while the subjects were resting in the supine position and holding their lung volume at normal end expiration. Tomography was performed on each subject from 120 projections of radioactivity in the lungs acquired with a rotating gamma camera. To minimize lung motion artifacts, the subjects were asked to hold their breath at end expiration during the 10-s duration of data acquisition in each projectional angle. Perfusion images of lung slices (11 mm thick) were reconstructed, and the radioactivity within each slice was expressed per unit lung volume of 3.7 X 3.7 X 11 mm. Perfusion images of a midcoronal slice from each subject manifested a concentric pattern of radioactivity that decreased significantly from the center to the periphery, suggesting that blood flow rate per unit lung volume was up to 10 times larger near the central region. This gradient in activity between the center and the periphery of the coronary slices was gravity independent as the subjects were supine. Images of sagittal slices from the middle of the right lung also manifested a similar pattern of concentric gradient in activity, with the vertical distribution (gravity related) almost comparable with the horizontal distribution (gravity independent). These results indicate that pulmonary blood flow in resting supine humans is spatially stratified with a marked central-to-peripheral gradient in all directions. It appears that zone 4 (reduced blood flow) is not a phenomenon limited to the dependent region of the lung as commonly thought but rather is a manifestation of this spatial distribution whereby blood flow is lowest in all peripheral regions of the lung.
利用99mTc标记的人血白蛋白大聚合体（99mTc-MAA）对6名健康受试者进行肺部单光子发射计算机断层扫描，以研究肺血流的三维分布。在受试者仰卧休息且肺容积保持在正常呼气末时注射99mTc-MAA。使用旋转γ相机从肺部放射性的120个投影对每个受试者进行断层扫描。为了尽量减少肺部运动伪影，要求受试者在每个投影角度的数据采集10秒期间呼气末屏气。重建肺切片（11毫米厚）的灌注图像，并将每个切片内的放射性表示为每3.7×3.7×11毫米肺容积单位的放射性。每个受试者的中冠状面切片的灌注图像显示出放射性的同心模式，从中心到周边显著降低，这表明每单位肺容积的血流速率在中心区域附近高达周边区域的10倍。由于受试者处于仰卧位，冠状切片中心和周边之间的这种放射性梯度与重力无关。右肺中部矢状面切片的图像也显示出类似的同心放射性梯度模式，垂直分布（与重力有关）与水平分布（与重力无关）几乎相当。这些结果表明，静息仰卧位人体的肺血流在空间上呈分层分布，在所有方向上都有明显的从中心到周边的梯度。似乎4区（血流减少）并非如通常所认为的那样仅限于肺的下垂区域，而是这种空间分布的一种表现，即肺的所有周边区域血流最低。
