Progression of Emphysema Evaluated by MRI Using Hyperpolarized 3He (Hp 3He) Measurements in Patients with Alpha-1-Antitrypsin (A1AT) Deficiency Compared with CT and Lung Function Tests

Background: The progression of emphysema is traditionally measured by pulmonary function test, with forced expiratory volume in 1 s (FEV1) being the most accepted and used measurement. However, FEV1 is insensitive in detecting mild/slow progression of emphysema because of low reproducibility as compared to yearly decline. Purpose: To investigate the progression of emphysema over a period of 2 years using diffusion-weighted hyperpolarized (HP) He-3 magnetic resonance imaging (MRI) in patients with alpha-1-antitrypsin (A1AT) deficiency. Material and Methods: Nine patients with severe A1AT deficiency were studied over a period of 2 years (baseline, year 1, and year 2) with Hp He-3 MRI using apparent diffusion coefficient (ADC), lung function tests (FEV1 and carbon monoxide lung diffusion capacity [D-L,D-CO]), and computed tomography (CT) using densitometric parameters (15th percentile density [CT-PD15] and relative area of emphysema below -910 HU [CT-RA-910]). Results: Seven patients were scanned three times, one patient two times, and one patient only at baseline. The mean increase in ADC values from first to last Hp He-3 MR scanning was 3.8% (0.014 cm (2)/s [SD 0.024 cm(2)/s]; not significant). The time trends for FEV1, D-L,D-CO, CT-PD15, and CT-RA-910 were all statistically significant. We found a high correlation between ADC and D-L,D-CO (P<0.001). Conclusion: This pilot study indicates the possible use of nonionizing HP He-3 MRI for monitoring the progression of emphysema. However, in the future, larger studies are needed to confirm these preliminary results.