PurposeInterest in using T1 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 T1 of the lung parenchyma in asymptomatic current smokers.Materials and MethodsLung T1 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 T1, with similar T1 measurement protocols. A backward linear model of T1 as a function of FEV1, FVC, weight, height, age and PY was tested.ResultsA significant correlation between lung T1 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 T1 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).ConclusionsA correlation between lung T1 and PY when adjusted for both age and height was found, and T1 of the lung shortens with ageing. Accordingly, PY and age can be significant confounding factors when T1 is used as a biomarker in lung MRI studies that must be taken into account to detect underlying patterns of disease.

Purpose: As several studies have provided evidence that lung disease affects the T1 of the human lung, our purpose was to investigate the effect of age on the T1-relaxation time in the lungs of healthy never-smokers, including group difference between sexes. Materials and methods: The Snapshot FLASH pulse sequence (inversion recovery with multiple gradient echo read-outs) was used to quantify lung T1 in 30 healthy neversmoking volunteers at 1.5 Tesla. Measurements were performed under breath hold of a tidal inspiration. Additionally, subjects underwent clinical MRI and pulmonary function tests. A linear regression model of T1 as a function of age and sex was tested. Results: The slope of lung T1 at tidal end-inspiration as a function of age was statistically different between males and females (p<0.001). In a linear regression model of T1 as a function of age and sex, females have slope of -4.1 ms/year (95% CI= [-5.2,-3.0]) at p < 0.001, and males -0.064 ms/year (95% CI=[-1.2,1.1]) at p=0.9, with a whole model R 2 = 0.83. Conclusion:The observed dependencies of lung T1 on age and sex are here attributed to a previously reported difference in blood T1 between sexes, and a previously reported decrease of pulmonary blood volume with increasing age. This may have implications for the interpretation of lung T1 measurements in both healthy individuals and patients.

BackgroundAirspace Dimension Assessment with inhaled nanoparticles is a novel method to determine distal airway morphology. This is the first empirical study using Airspace Dimension Assessment with nanoparticles (AiDA) to estimate distal airspace radius. The technology is relatively simple and potentially accessible in clinical outpatient settings.MethodNineteen never-smoking volunteers performed nanoparticle inhalation tests at multiple breath-hold times, and the difference in nanoparticle concentration of inhaled and exhaled gas was measured. An exponential decay curve was fitted to the concentration of recovered nanoparticles, and airspace dimensions were assessed from the half-life of the decay. Pulmonary tissue density was measured using magnetic resonance imaging (MRI).ResultsThe distal airspace radius measured by AiDA correlated with lung tissue density as measured by MRI (ρ = −0.584; p = 0.0086). The linear intercept of the logarithm of the exponential decay curve correlated with forced expiratory volume in one second (FEV1) (ρ = 0.549; p = 0.0149).ConclusionThe AiDA method shows potential to be developed into a tool to assess conditions involving changes in distal airways, eg, emphysema. The intercept may reflect airway properties; this finding should be further investigated.

ObjectiveOxygen enhanced pulmonary MRI is a promising modality for functional lung studies and has been applied to a wide range of pulmonary conditions. The purpose of this study was to characterize the oxygen enhancement effect in the lungs of healthy, never-smokers, in light of a previously established relationship between oxygen enhancement and diffusing capacity of carbon monoxide in the lung (DL,CO) in patients with lung disease.MethodsIn 30 healthy never-smoking volunteers, an inversion recovery with gradient echo read-out (Snapshot-FLASH) was used to quantify the difference in longitudinal relaxation rate, while breathing air and 100% oxygen, ΔR1, at 1.5 Tesla. Measurements were performed under multiple tidal inspiration breath-holds.ResultsIn single parameter linear models, ΔR1 exhibit a significant correlation with age (p = 0.003) and BMI (p = 0.0004), but not DL,CO (p = 0.33). Stepwise linear regression of ΔR1 yields an optimized model including an age-BMI interaction term.ConclusionIn this healthy, never-smoking cohort, age and BMI are both predictors of the change in MRI longitudinal relaxation rate when breathing oxygen. However, DL,CO does not show a significant correlation with the oxygen enhancement. This is possibly because oxygen transfer in the lung is not diffusion limited at rest in healthy individuals. This work stresses the importance of using a physiological model to understand results from oxygen enhanced MRI.

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