title: Monitoring redox-sensitive paramagnetic contrast agent by EPRI, OMRI and MRI.
abstract: A comparative study of tissue redox-status imaging using commonly used redox sensitive nitroxides has been carried out using electron paramagnetic resonance imaging (EPRI), Overhauser magnetic resonance imaging (OMRI) and conventional T(1)-weighted magnetic resonance imaging, MRI. Imaging studies using phantoms of different nitroxides at different concentration levels showed that EPRI and OMRI sensitivities were found to be linearly dependent on line width of nitroxides up to 2 mM, and the enhancement in MRI intensity was linear up to 5 mM. The sensitivity and resolution of EPRI and OMRI images depended significantly on the line width of the nitroxides whereas the MRI images were almost independent of EPR line width. Reduction of the paramagnetic 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (3CP) by ascorbic acid (AsA) to the diamagnetic by hydroxylamine was monitored from a sequence of temporal images, acquired using the three imaging modalities. The decay rates determined by all the three modalities were found to be similar. However the results suggest that T(1)-weighted MRI can monitor the redox status, in addition to providing detailed anatomical structure in a short time. Therefore, a combination of MRI with nitroxides as metabolically responsive contrast agents can be a useful technique for the in vivo imaging probing tissue redox status.
authors.affiliation: Radiation Biology Branch, Center for Cancer Research, National Cancer Institute, Building 10, Room B3B69, NIH, Bethesda, MD 20892-1002, USA.
authors.forename: Fuminori
authors.initials: F
authors.lastname: Hyodo
authors.forename: Ramachandran
authors.initials: R
authors.lastname: Murugesan
authors.forename: Ken-ichiro
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Emi
authors.initials: E
authors.lastname: Hyodo
authors.forename: Sankaran
authors.initials: S
authors.lastname: Subramanian
authors.forename: James B
authors.initials: JB
authors.lastname: Mitchell
authors.forename: Murali C
authors.initials: MC
authors.lastname: Krishna
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry; D003287:Contrast Media / Q000737:chemistry*; D003497:Cyclic N-Oxides / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D019786:Gadolinium DTPA / Q000737:chemistry; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009589:Nitrogen Oxides / Q000737:chemistry*; D010084:Oxidation-Reduction; D019047:Phantoms, Imaging; D011759:Pyrrolidines / Q000737:chemistry*; D014216:Triacetoneamine-N-Oxyl / Q000737:chemistry
chemical_list: D003287:Contrast Media; D003497:Cyclic N-Oxides; D009589:Nitrogen Oxides; D011759:Pyrrolidines; D014216:Triacetoneamine-N-Oxyl; C077426:3-carbamoyl-2,2,5,5-tetramethyl-1-pyrrolidinyl-N-oxyl; D019786:Gadolinium DTPA; D001205:Ascorbic Acid; C003959:TEMPO