Elsevier

Academic Radiology

Volume 12, Issue 11, November 2005, Pages 1385-1393
Academic Radiology

Pulmonary functional imaging
Detection of Age-Dependent Changes in Healthy Adult Lungs With Diffusion-Weighted 3He MRI

https://doi.org/10.1016/j.acra.2005.08.005Get rights and content

Rationale and Objectives

To investigate changes in lung microstructure in healthy adult subjects with no smoking history using diffusion-weighted 3He MRI.

Materials and Methods

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).

Results

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 cm2s−1y−1; UVa, +0.0015 cm2s−1y−1; pooled, +0.0015 cm2s−1y−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.

Conclusion

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.

Section snippets

Patient Selection

Subjects from three sites (UVa, N = 25; UW, N = 8; UN, N = 11) were included in this analysis; demographic information for the three groups is listed in Table 1. Inclusion criteria were similar for subjects across the three sites. These included forced expiratory volume at 1 second (FEV1) > 80% predicted, FEV1/forced vital capacity (FVC) > 0.70, and normal chest findings on physical examination or radiograph. Subjects with a personal smoking history, defined as smoking more than 100 cigarettes

Results

Regional ADC maps and histograms of ADC values from the entire lung, typical of ADC measures obtained from the UVa and UW sites, are shown in Figure 1 for two healthy subjects near the extremes of the age range studied (23 and 69 years). Regions of elevated ADCs are shown in progressively warmer colors. Histograms show an elevated mean ADC in the older subject compared with the younger subject (0.25 vs 0.17 cm2/s), with a more modest increase in the SD (0.11 vs 0.10 cm2/s). Representative ADC

Discussion

Noninvasive techniques for probing regional changes in lung microstructure are needed to quantify the onset and progression of such lung diseases as emphysema and pulmonary fibrosis. This study combines work from three different sites and shows a reproducible increase in ADC with increasing age for healthy individuals who never smoked. A monoexponential model for diffusion-weighted signal loss was used to calculate the ADC for data from all three sites. Because the techniques measure the

Acknowledgment

The authors thank the staff and students from the School of Physics and Astronomy at University of Nottingham who agreed to take part in this study; Dawn Jotham for lung function measurements; and Kelli Hellenbrand, MR technologist, and Sandy Fuller, RN, for their valuable assistance.

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  • Cited by (0)

    Supported in part by EPSRC (PhD studentship, B.W.), the Wellcome Trust (3He gas polarizer), and the MRC (MR scanner; J.O.-B.); GE Health Care (T.M.G., S.B.F., F.R.K.); Sandler Foundation for Asthma Research (S.B.F.); and grant no. IN2002-01 from the Commonwealth of Virginia Technology Research Fund (T.A.A., J.P.M.).

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