A Model for Predicting Future FEV1 Decline in Smokers Using Hyperpolarized ³He Magnetic Resonance Imaging

The purpose of this study was to assess the effectiveness of hyperpolarized helium-3 magnetic resonance (MR)-based imaging markers in predicting future forced expiratory volume in one second decline/chronic obstructive pulmonary disorder progression in smokers compared to current diagnostic techniques.

Total 60 subjects (15 nonsmokers and 45 smokers) participated in both baseline and follow-up visits (∼1.4 years apart). At both visits, subjects completed pulmonary function testing, a six-minute walk test , and the St. George Respiratory Questionnaire. Using helium-3 MR imaging, means (M) and standard deviations (H) of oxygen tension (P_AO₂), fractional ventilation, and apparent diffusion coefficient were calculated across 12 regions of interest in the lungs. Subjects who experienced FEV1 decline >100 mL/year were deemed "decliners," while those who did not were deemed "sustainers." Nonimaging and imaging prediction models were generated through a logistic regression model, which utilized measurements from sustainers and decliners.

The nonimaging prediction model included the St. George Respiratory Questionnaire total score, diffusing capacity of carbon monoxide by the alveolar volume (DLCO/VA), and distance walked in a six-minute walk test. A receiving operating character curve for this model yielded a sensitivity of 75% and specificity of 68% with an overall area under the curve of 65%. The imaging prediction model generated following the same methodology included ADC^H, FV^H, and P_AO₂^H. The resulting receiving operating character curve yielded a sensitivity of 87.5%, specificity of 82.8%, and an area under the curve of 89.7%.

The imaging predication model generated from measurements obtained during ³He MR imaging is better able to predict future FEV1 decline compared to one based on current clinical tests and demographics. The imaging model's superiority appears to arise from its ability to distinguish well-circumscribed, severe disease from a more uniform distribution of moderately altered lung function, which is more closely associated with subsequent FEV1 decline.