title: In vivo high-resolution 3D overhauser-enhanced MRI in mice at 0.2 T.
abstract: Overhauser-enhanced MRI (OMRI) offers the potentiality of detecting low-concentrated species generated by specific biological processes. However molecular imaging applications of OMRI need significant improvement in spatial localization. Here it is shown that 3D-OMRI of a free radical injected in tumor-bearing mice can be performed at high anatomical resolution at a constant field. A 30 mm cavity operating at 5.43 GHz was inserted in a C-shaped magnet for proton MRI at 0.194 T. Nude mice with or without brain-implanted C6 rat glioma were positioned in the cavity and injected with TOPCA (1-oxyl-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrole-3-carboxylic acid). OMRI was performed in 3D within several minutes in the brain region without high overheating of the animals. Voxel size was 0.5 × 0.5 × 1 mm³ , providing good delineation of brain regions. Signal amplifications ranged from 2 in tumors to 10 in vessels several minutes after TOPCA injection. Time-course of signal enhancement could be measured by 2D OMRI at 15 s time intervals in a localized thin slice. The method opens the way for molecular imaging of biological activities able to generate OMRI-visible free radicals.
authors.affiliation: CRMSB, UMR 5536, University Bordeaux Segalen, CNRS, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Massot
authors.forename: Elodie
authors.initials: E
authors.lastname: Parzy
authors.forename: Line
authors.initials: L
authors.lastname: Pourtau
authors.forename: Philippe
authors.initials: P
authors.lastname: Mellet
authors.forename: Guillaume
authors.initials: G
authors.lastname: Madelin
authors.forename: Sylvain
authors.initials: S
authors.lastname: Marque
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Franconi
authors.forename: Eric
authors.initials: E
authors.lastname: Thiaudiere
mesh_terms: D000818:Animals; D001831:Body Temperature; D001932:Brain Neoplasms / Q000737:chemistry / Q000473:pathology*; D045744:Cell Line, Tumor / Q000637:transplantation; D003287:Contrast Media / Q000008:administration & dosage / Q000032:analysis* / Q000493:pharmacokinetics; D003497:Cyclic N-Oxides / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D005240:Feasibility Studies; D005609:Free Radicals / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics; D005910:Glioma / Q000737:chemistry / Q000473:pathology*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007275:Injections, Intravenous; D008279:Magnetic Resonance Imaging / Q000379:methods*; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D011522:Protons; D011758:Pyrroles / Q000008:administration & dosage / Q000032:analysis / Q000493:pharmacokinetics; D051381:Rats; D014183:Transplantation, Heterologous; D014867:Water
chemical_list: C572943:1-oxyl-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrole-3-carboxylic acid; D003287:Contrast Media; D003497:Cyclic N-Oxides; D005609:Free Radicals; D011522:Protons; D011758:Pyrroles; D014867:Water