title: Electron paramagnetic resonance imaging of tumor pO₂.
abstract: Electron paramagnetic resonance imaging (EPRI) can be used to noninvasively and quantitatively obtain three-dimensional maps of tumor pO₂. The paramagnetic tracer triarylmethyl (TAM), a substituted trityl radical moiety, is not toxic to animals and provides narrow isotropic spectra, which is ideal for in vivo EPR imaging experiments. From the oxygen-induced spectral broadening of TAM, pO₂ maps can be derived using EPRI. The instrumentation consists of an EPRI spectrometer and 7T magnetic resonance imaging (MRI) system both operating at a common radiofrequency of 300 MHz. Anatomic images obtained by MRI can be overlaid with pO₂ maps obtained from EPRI. With imaging times of less than 3 min, it was possible to monitor the dynamics of oxygen changes in tumor and distinguish chronically hypoxic regions from acutely hypoxic regions. In this article, the principles of pO₂ imaging with EPR and some relevant examples of tumor imaging are reviewed.
authors.affiliation: Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, National Institute of Health, Bethesda, Maryland 20892, USA. murali@helix.nih.gov
authors.forename: Murali C
authors.initials: MC
authors.lastname: Krishna
authors.forename: Shingo
authors.initials: S
authors.lastname: Matsumoto
authors.forename: Hironobu
authors.initials: H
authors.lastname: Yasui
authors.forename: Keita
authors.initials: K
authors.lastname: Saito
authors.forename: Nallathamby
authors.initials: N
authors.lastname: Devasahayam
authors.forename: Sankaran
authors.initials: S
authors.lastname: Subramanian
authors.forename: James B
authors.initials: JB
authors.lastname: Mitchell
mesh_terms: D000818:Animals; D001565:Benzoates / Q000633:toxicity; D015687:Cell Hypoxia; D004578:Electron Spin Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D006019:Glycolysis; D006575:Heterocyclic Compounds, 3-Ring / Q000633:toxicity; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000502:physiology; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods; D051379:Mice; D008954:Models, Biological; D009363:Neoplasm Proteins / Q000502:physiology; D009369:Neoplasms / Q000098:blood supply / Q000378:metabolism / Q000473:pathology* / Q000532:radiotherapy; D009374:Neoplasms, Experimental / Q000098:blood supply / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy; D009389:Neovascularization, Pathologic / Q000378:metabolism / Q000503:physiopathology; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000295:instrumentation / Q000379:methods; D010100:Oxygen / Q000032:analysis; D010313:Partial Pressure; D011836:Radiation Tolerance; D013113:Spin Labels; D014320:Triphenylmethyl Compounds / Q000633:toxicity; D059016:Tumor Microenvironment
chemical_list: D001565:Benzoates; D006575:Heterocyclic Compounds, 3-Ring; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009363:Neoplasm Proteins; D013113:Spin Labels; D014320:Triphenylmethyl Compounds; D010100:Oxygen