Detection of regional radiation-induced lung injury using hyperpolarized (129)Xe chemical shift imaging in a rat model involving partial lung irradiation: Proof-of-concept demonstration

PURPOSE: The purpose of this work was to use magnetic resonance imaging (MRI) of hyperpolarized (HP) (129)Xe dissolved in pulmonary tissue (PT) and red blood cells (RBCs) to detect regional changes to PT structure and perfusion in a partial-lung rat model of radiation-induced lung injury and compare with histology. METHODS AND MATERIALS: The right medial region of the lungs of 6 Sprague-Dawley rats was irradiated (20 Gy, single-fraction). A second nonirradiated cohort served as the control group. Imaging was performed 4 weeks after irradiation to quantify intensity and heterogeneity of PT and RBC (129)Xe signals. Imaging findings were correlated with measures of PT and RBC distribution. RESULTS: Asymmetric (right vs left) changes in (129)Xe signal intensity and heterogeneity were observed in the irradiated cohort but were not seen in the control group. PT signal was observed to increase in intensity and heterogeneity and RBC signal was observed to increase in heterogeneity in the irradiated right lungs, consistent with histology. CONCLUSION: Regional changes to PT and RBC (129)Xe signals are detectable 4 weeks following partial-lung irradiation in rats.