title: Magnetic resonance imaging of the tumor microenvironment in radiotherapy: perfusion, hypoxia, and metabolism.
abstract: The tumor microenvironment is characterized by hypoxia, low pH, and high interstitial fluid pressure. Hypoxic regions in tumors with low partial pressure of oxygen (pO2) levels can result in resistance to radiotherapy, thus causing local failure. Therefore, it would be desirable to noninvasively measure pO2 levels in the tumor before, during, and after treatment to better customize therapy and follow treatment response. Several techniques used in preclinical and clinical studies to obtain the pO2 status of tissue, such as dynamic contrast-enhanced magnetic resonance imaging, blood oxygen level-dependent imaging, and electron paramagnetic resonance imaging, are reviewed. Furthermore, the ability to hyperpolarize specific metabolic substrates that are isotopically labeled with (13)C coupled with magnetic resonance spectroscopy enables noninvasive imaging of tissue metabolism, such as glycolysis.
authors.affiliation: Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Matsuo
authors.affiliation: Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Shingo
authors.initials: S
authors.lastname: Matsumoto
authors.affiliation: Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: James B
authors.initials: JB
authors.lastname: Mitchell
authors.affiliation: Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD.
authors.forename: Murali C
authors.initials: MC
authors.lastname: Krishna
authors.affiliation: Radiation Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD. Electronic address: camphauk@mail.nih.gov.
authors.forename: Kevin
authors.initials: K
authors.lastname: Camphausen
mesh_terms: D000818:Animals; D015687:Cell Hypoxia; D004578:Electron Spin Resonance Spectroscopy; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy; D009369:Neoplasms / Q000175:diagnosis* / Q000378:metabolism*; D018787:Radiation Oncology / Q000379:methods; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D059016:Tumor Microenvironment