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

Abstract 

Purpose

To 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 materials

In 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 1week prior to and 3months 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.

Results

On 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%).

Conclusions

This 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.

Keywords: Hyperpolarized helium-3 MRI, Radiation therapy, Pulmonary, Pneumonitis, Normal tissue injury