Fichele Stanislao, Woodhouse Neil, Swift Andrew J, Said Zead, Paley Martyn N J, Kasuboski Larry, Mills Gary H, van Beek Edwin J R, Wild Jim M
Academic Unit of Radiology, The University of Sheffield, Royal Hallamshire Hospital, Glossop Road, Sheffield S10 2JF, UK.
J Magn Reson Imaging. 2004 Aug;20(2):331-5. doi: 10.1002/jmri.20104.
To probe the variation of alveolar size in healthy lung tissue as a function of posture using diffusion-weighted helium-3 hyperpolarized gas imaging.
Measurements of the helium-3 apparent diffusion coefficient (ADC) were made on six healthy subjects. These were used to show the variation of alveolar size between the lowermost dependent regions of the lung compared to the uppermost regions of the lung in four postures: supine, prone, left-lateral decubitus, and right-lateral decubitus.
The distribution of acinar size in the lungs was found to be heterogeneous, and influenced by lung orientation. In nearly all postures, the ADC was significantly higher in the non-dependent uppermost regions of the lung compared to the dependent lowermost regions of the lung; the greatest variation was found in the left-lateral decubitus position. The difference in ADC between uppermost and lowermost regions was on average 0.012 cm(2)second(-1), which represents 20% of the average ADC value for the whole lung. A systematic decrease in ADC from the apex of the lung to the base was also found, which corresponds to an inherent gradient in alveolar size.
The posture dependent variations in ADC were attributed to compression of the parenchyma under its own weight and the mass of the heart.
使用扩散加权超极化氦-3气体成像技术探究健康肺组织中肺泡大小随体位的变化。
对6名健康受试者进行氦-3表观扩散系数（ADC）测量。这些测量用于显示在仰卧位、俯卧位、左侧卧位和右侧卧位四种体位下，肺最下部依赖区域与最上部区域之间肺泡大小的变化。
发现肺腺泡大小分布不均一，且受肺方向影响。在几乎所有体位下，肺非依赖的最上部区域的ADC显著高于依赖的最下部区域；左侧卧位时差异最大。最上部和最下部区域之间的ADC差异平均为0.012 cm²·秒⁻¹，占全肺平均ADC值的20%。还发现从肺尖到肺底ADC有系统性降低，这与肺泡大小的固有梯度相对应。
ADC的体位依赖性变化归因于实质在自身重量和心脏质量作用下的压缩。
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