[Show abstract][Hide abstract] ABSTRACT: To investigate changes in lung microstructure in healthy adult subjects with no smoking history using diffusion-weighted 3He MRI.
Diffusion magnetic resonance imaging using hyperpolarized helium 3 (3He) was applied to healthy volunteers to explore the dependence of lung microstructural changes with age, reflected by changes in the apparent diffusion coefficient (ADC) of 3He in lung air spaces. Data from three sites (University of Virginia (UVa), N = 25; University of Wisconsin (UW), N = 8; University of Nottingham (UN), N = 11) were combined in pooled analysis, including a total of N = 44 subjects (age range, 18-69 years; average age, 41.7 +/- 16.7 years).
ADC was found to depend on age at all three sites (UW, R = +0.95, P = .0003; UVa, R = +0.74, P < .0001; UN, R = +0.96, P < .0001). Increases in mean ADCs with age appeared similar across sites (UW, +0.0017 cm2 s(-1) y(-1); UVa, +0.0015 cm2 s(-1) y(-1); pooled, +0.0015 cm2 s(-1) y(-1); P = .71). In a regional analysis performed on UW data, the increase in ADC affected all regions of the lung, but the apical and middle regions showed a greater increase compared with the base of the lung.
Results suggest the observed age dependence of the ADC may be caused by changes in lung microstructure that increase alveolar volume during the aging process.
[Show abstract][Hide abstract] ABSTRACT: The geometry and morphometry of intraacinar airways in human lungs were studied on silicone rubber casts from two adult lungs. We defined acini as the complex of alveolated airways distal to the terminal bronchioles--that is, beginning with the first-order respiratory or transitional bronchiole. The morphological properties of pulmonary acini are described. The acinar volume averages 187 mm3 (SD +/- 79 mm3). Intraacinar airways branch dichotomously over about 9 generations (range 6-12). The internal airway diameter falls from 500 micron to 270 micron between acinar generations 0 and 10, whereas the outer diameter (including the sleeve of alveoli) remains constant at 700 micron. Towards the periphery the size of alveoli increases and clusters of alveoli become more numerous. The longitudinal path length of acinar airways (defined as the distance along the ducts from the transitional bronchiole to the alveolar sacs) averages 8.8 mm (+/- 1.4 mm). The morphometric data collected in this study are used to construct an idealized model of human acinar airways that can be related to existing models of the human bronchial tree.
The Anatomical Record 04/1988; 220(4):401-14. DOI:10.1002/ar.1092200410
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