Published ahead of print on January 26, 2006, doi:10.1164/rccm.200411-1595OC Am. J. Respir. Crit. Care Med., Volume 173, Number 8, April 2006, 847-851 A more recent version of this article appeared on April 15, 2006
Submitted on November 29, 2004 Acinar Structure in Symptom-Free Adults by Helium-3 Magnetic ResonanceBarnaby Waters1,1 School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom, 2 Department of Infection, Immunity and Inflammation (Child Health), University of Leicester, Leicester, United Kingdom * To whom correspondence should be addressed. E-mail: ms70{at}le.ac.uk.
Rationale - The apparent diffusion coefficient of hyperpolarized 3He in the lungs has been shown to correlate directly in animal models with the peripheral airspace size and can detect changes in lung microstructure. Objectives - To study in vivo the 3He apparent diffusion coefficient and to demonstrate its sensitivity to changes in lung morphometry as a result of ageing, exposure to cigarette smoke and lung inflation. Methods - We assessed the variation in the diffusion of hyperpolarized 3He gas in the lungs by magnetic resonance techniques. Spirometric lung volumes were recorded. Measurements - We measured the dependence of 3He diffusion on age and on reported cigarette smoke exposure in 32 symptom-free adults. We also measured the dependence of the apparent diffusion coefficient on the degree of lung inflation. Results - In healthy never-smokers the apparent diffusion coefficient increased with age from 0.115 to 0.155 cm2s-1 at 20 and 70 years respectively, increased linearly with lung inflation and was independent of individual's lung size after correcting for age. For active and passive smokers the apparent diffusion coefficient increased by up to 40% compared to never-smokers with mean values significantly higher (p =0.016 and p =0.0007 respectively). Conclusions - Peripheral airspace size increases with age and after exposure to smoke in healthy adults in agreement with previous histological studies. We have confirmed in vivo that peripheral airspace size is independent of inter-subject lung size. Key words: Diffusion, age, smoking, hyperpolarized, noble gas.
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