Hyperpolarised 3He MRI versus HRCT in COPD and normal volunteers: PHIL trial

The aim of the present study was to apply hyperpolarised (Hp) He-3 magnetic resonance imaging (MRI) to identify patients with chronic obstructive pulmonary disease (COPD) and alpha(1)-antitrypsin deficiency (alpha(1)-ATD) from healthy volunteers and compare Hp He-3 MRI findings with high-resolution computed tomography (HRCT) in a multicentre study. Quantitative measurements of Hp He-3 MRI (apparent diffusion coefficient (ADC)) and HRCT (mean lung density (MLD)) were correlated with pulmonary function tests. A prospective three centre study enrolled 122 subjects with COPD (either acquired or genetic) and age-matched never-smokers. All diagnostic studies were completed in 94 subjects (52 with COPD; 13 with alpha(1)-ATD; 29 healthy subjects; 63 males; and 31 females; median age 62 yrs). The consensus assessment of radiologists, blinded for other test results, estimated nonventilated lung volume (Hp He-3 MRI) and percentage diseased lung (HRCT). Quantitative evaluation of all data for each centre consisted of ADC (Hp He-3 MRI) and MLD measurements (HRCT), and correlation with forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) indicating airway obstruction, and the diffusing capacity of the lung for carbon monoxide (DL,CO) indicating alveolar destruction. Using lung function tests as a reference, regional analysis of Hp He-3 MRI and HRCT correctly categorised normal volunteers in 100% and 97%, COPD in 42% and 69% and alpha(1)-ATD in 69% and 85% of cases, respectively. Direct comparison of Hp He-3 MRI and CT revealed 23% of subjects with moderate/severe structural abnormalities had only mild ventilation defects. In comparison with lung function tests, ADC was more effective in separating COPD patients from healthy subjects than MLD (p<0.001 versus 0.038). ADC measurements showed better correlation with DL,CO than MLD (r=0.59 versus 0.29). Hyperpolarlsed He-3 MRI correctly categorised patients with COPD and normal volunteers. It offers additional functional information, without the use of lonising radiation whereas HRCT gives better morphological information. We showed the feasibility of a multicentre study using different magnetic resonance systems.