Detection of radiation-induced lung injury in non-small cell lung cancer patients using hyperpolarized helium-3 magnetic resonance imaging

PurposeTo compare hyperpolarized helium-3 magnetic resonance imaging (3He-MRI) acquired from non-small cell lung cancer (NSCLC) patients before and after external beam radiotherapy (EBRT).Methods and materialsIn an Ethics Committee-approved prospective study, five patients with histologically confirmed NSCLC gave written informed consent to undergo computed tomography (CT) and 3He-MR ventilation imaging 1 week prior to and 3 months after radiotherapy. Images were registered to pre-treatment CT using anatomical landmark-based rigid registration to enable comparison. Emphysema was graded from examination of the CT. MRI-defined ventilation was calculated as the intersection of 3He-MRI and CT lung volume as a percentage of the CT lung volume for the whole lung and regions of CT-defined pneumonitis.ResultsOn pre-treatment images, there was a significant correlation between the degree of CT-defined emphysema and 3He-MRI whole lung ventilation (Spearman’s rho = 0.90, p = 0.04). After radiation therapy, pneumonitis was evident on CT for 3/5 patients. For these cases, 3He-MRI ventilation was significantly reduced within the regions of pneumonitis (pre: 94.1 ± 2.2%, post: 73.7 ± 4.7%; matched pairs Student’s t-test, p = 0.02, mean difference = 20.4%, 95% confidence interval 6.3–34.6%).ConclusionsThis work demonstrates the feasibility of detecting ventilation changes between pre- and post-treatment using hyperpolarized helium-3 MRI for patients with NSCLC. Pre-treatment, the degree of emphysema and 3He-MRI ventilation were correlated. For three cases of radiation pneumonitis, 3He-MRI ventilation changes between pre- and post-treatment imaging were consistent with CT evidence of radiation-induced lung injury.