T1 Relaxation Time in Lungs of Asymptomatic Smokers

Purpose Interest in using T-1 as a potential MRI biomarker of chronic obstructive pulmonary disease (COPD) has recently increased. Since tobacco smoking is the major risk factor for development of COPD, the aim for this study was to examine whether tobacco smoking, pack-years (PY), influenced T-1 of the lung parenchyma in asymptomatic current smokers. Materials and Methods Lung T-1 measurements from 35 subjects, 23 never smokers and 12 current smokers were retrospectively analyzed from an institutional review board approved study. All 35 subjects underwent pulmonary function test (PFT) measurements and lung T-1, with similar T-1 measurement protocols. A backward linear model of T-1 as a function of FEV1, FVC, weight, height, age and PY was tested. Results A significant correlation between lung T-1 and PY was found with a negative slope of -3.2 ms/year (95% confidence interval [CI] [-5.8, -0.6], p = 0.02), when adjusted for age and height. Lung T-1 shortens with ageing among all subjects, -4.0 ms/year (95% CI [-6.3, -1.7], p = 0.001), and among the never smokers, -3.7 ms/ year (95% CI [-6.0, -1.3], p = 0.003). Conclusions A correlation between lung T1 and PY when adjusted for both age and height was found, and T-1 of the lung shortens with ageing. Accordingly, PY and age can be significant confounding factors when T-1 is used as a biomarker in lung MRI studies that must be taken into account to detect underlying patterns of disease.