Early emphysematous changes in asymptomatic smokers:: Detection with 3He MR imaging

Purpose: To prospectively compare apparent diffusion coefficient (ADC) measurements derived from diffusion-weighted hyperpolarized helium 3 (He-3) magnetic resonance (MR) imaging with functional and structural findings using spirometric tests and thin-section computed tomography (CT) of the lungs in asymptomatic smokers and healthy nonsmokers of similar age. Materials and Methods: All studies were HIPAA compliant and were approved by the institutional review board. Informed consent was obtained. Ventilation and diffusion-weighted He-3 MR images were obtained in healthy subjects: 11 smokers (five women, six men; mean age, 47 years +/- 18 [standard deviation]; range, 23 - 73 years) and eight nonsmokers (< 100 cigarettes in lifetime) (four women, four men; mean age, 46 years +/- 16; range, 23 - 69 years). Mean ADC values for smokers and nonsmokers were compared with spirometric values, diffusing capacity of the lung for carbon monoxide (D-LCO), age, and pack-years with Spearman rank correlation coefficient (r(s)) and multiple linear regression analysis. Mean ADC value and thin-section CT emphysema index of relative area less than -950 HU (RA(950)) were compared on a regional basis by using linear mixed-effect models. Results: Mean ADC values and number of pack-years were significantly correlated (r(s) = 0.60; 95% confidence interval (CI): 0.21, 1.00; P = .007); relationship remained significant after adjustment for age (P = .003). D-LCO was strongly correlated with pack-years (r(s) = -0.63; 95% CI: -0.97, -0.29; P = .004). Negative correlations between mean ADC values and percentage predicted D-LCO (r(s) = -0.79; 95% CI: -0.93, -0.64; P <.001) and the ratio of forced expiratory volume in 1 second to forced vital capacity (r(s) = -0.72; 95% CI: -0.92, -0.52; P =.001) were statistically significant. Correlations between spirometric values or RA950 and number of pack-years were not significant (.05 level). Conclusion: Correlations between mean ADC values and pulmonary function test measurements for diagnosing emphysema, especially D-LCO, were statistically significant. (c) RSNA, 2006