Effects of age on pulmonary perfusion heterogeneity measured by magnetic resonance imaging

• Published in: Journal of applied physiology (1985) 2007-05, Vol.102 (5), p.2064-2070
• Main Authors: Levin, David L, Buxton, Richard B, Spiess, James P, Arai, Tatsuya, Balouch, Jamal, Hopkins, Susan R
• Format: Article
• Language: English
• Subjects: Adult; Aged; Aging; Aging - physiology; Biological and medical sciences; Cardiovascular system; Effects; Female; Fractals; Fundamental and applied biological sciences. Psychology; Humans; Image Processing, Computer-Assisted; Linear Models; Lung - blood supply; Magnetic Resonance Imaging - methods; Male; Middle Aged; NMR; Nuclear magnetic resonance; Pulmonary Circulation; Reference Values; Research Design; Respiratory Function Tests; Respiratory Physiological Phenomena; Respiratory system; Spin Labels
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00512.2006

1 Department of Radiology and 2 Division of Physiology, Department of Medicine, University of California, San Diego, La Jolla, California Submitted 5 May 2006 ; accepted in final form 26 January 2007 Normal aging is associated with a decline in pulmonary function and efficiency of gas exchange, although the effects on the spatial distribution of pulmonary perfusion are poorly understood. We hypothesized that spatial pulmonary perfusion heterogeneity would increase with increasing age. Fifty-six healthy, nonsmoking subjects (ages 21–76 yr) underwent magnetic resonance imaging with arterial spin labeling (ASL) using a Vision 1.5-T whole body scanner (Siemens Medical Systems, Erlangen, Germany). ASL uses a magnetically tagged bolus to generate perfusion maps where signal intensity is proportional to regional pulmonary perfusion. The spatial heterogeneity of pulmonary blood flow was quantified by the relative dispersion (RD = SD/mean, a global index of heterogeneity) of signal intensity for voxels within the right lung and by the fractal dimension ( D s ). There were no significant sex differences for RD ( P = 0.81) or D s ( P = 0.43) when age was considered as a covariate. RD increased significantly with increasing age by 0.1/decade until age 50–59 yr, and there was a significant positive relationship between RD and age ( R = 0.48, P < 0.0005) and height ( R = 0.39, P < 0.01), but not body mass index ( R = 0.07, P = 0.67). Age and height combined in a multiple regression were significantly related to RD ( R = 0.66, P < 0.0001). There was no significant relationship between RD and spirometry or arterial oxygen saturation. D s was not related to age, height, spirometry, or arterial oxygen saturation. The lack of relationship between age and D s argues against an intrinsic alteration in the pulmonary vascular branching with age as being responsible for the observed increase in global spatial perfusion heterogeneity measured by the RD. arterial spin labeling; pulmonary function; fractal dimension; relative dispersion Address for reprint requests and other correspondence: S. R. Hopkins, Physiology 0623A, Univ. of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0623 (e-mail: shopkins{at}ucsd.edu )