Pulmonary functional imagingDetection of Age-Dependent Changes in Healthy Adult Lungs With Diffusion-Weighted 3He MRI
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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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.).