title: Anatomical, functional and metabolic imaging of radiation-induced lung injury using hyperpolarized MRI.
abstract: MRI of hyperpolarized (129)Xe gas and (13)C-enriched substrates (e.g. pyruvate) presents an unprecedented opportunity to map anatomical, functional and metabolic changes associated with lung injury. In particular, inhaled hyperpolarized (129)Xe gas is exquisitely sensitive to changes in alveolar microanatomy and function accompanying lung inflammation through decreases in the apparent diffusion coefficient (ADC) of alveolar gas and increases in the transfer time (T(tr)) of xenon exchange from the gas and into the dissolved phase in the lung. Furthermore, metabolic changes associated with hypoxia arising from lung injury may be reflected by increases in lactate-to-pyruvate signal ratio obtained by magnetic resonance spectroscopic imaging following injection of hyperpolarized [1-(13)C]pyruvate. In this work, the application of hyperpolarized (129)Xe and (13)C MRI to radiation-induced lung injury (RILI) is reviewed and results of ADC, T(tr) and lactate-to-pyruvate signal ratio changes in a rat model of RILI are summarized. These results are consistent with conventional functional (i.e. blood gases) and histological (i.e. tissue density) changes, and correlate significantly with inflammatory cell counts (i.e. macrophages). Hyperpolarized MRI may provide an earlier indication of lung injury associated with radiotherapy of thoracic tumors, potentially allowing adjustment of treatment before the onset of severe complications and irreversible fibrosis.
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, Western University, London, Ontario, Canada; Department of Medical Biophysics, Western University, London, Ontario, Canada; Department of Medical Imaging, Western University, London, Ontario, Canada; Peter Gilgan Centre for Research and Learning, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Giles
authors.initials: G
authors.lastname: Santyr
authors.forename: Matthew
authors.initials: M
authors.lastname: Fox
authors.forename: Kundan
authors.initials: K
authors.lastname: Thind
authors.forename: Elaine
authors.initials: E
authors.lastname: Hegarty
authors.forename: Alexei
authors.initials: A
authors.lastname: Ouriadov
authors.forename: Michael
authors.initials: M
authors.lastname: Jensen
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Scholl
authors.forename: Jacob
authors.initials: J
authors.lastname: Van Dyk
authors.forename: Eugene
authors.initials: E
authors.lastname: Wong
mesh_terms: D000818:Animals; D002247:Carbon Isotopes; D006801:Humans; D055370:Lung Injury / Q000378:metabolism* / Q000473:pathology* / Q000503:physiopathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011832:Radiation Injuries / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology*; D014979:Xenon Isotopes
chemical_list: D002247:Carbon Isotopes; D014979:Xenon Isotopes
keywords: MRI; diffusion; gas exchange; hyperpolarized; hypoxia; lung injury; macrophages; radiotherapy