title: Artifact suppression in electron paramagnetic resonance imaging of (14)N- and (15)N-labeled nitroxyl radicals with asymmetric absorption spectra.
abstract: This article describes an improved method for suppressing image artifacts in the visualization of (14)N- and (15)N-labeled nitroxyl radicals in a single image scan using electron paramagnetic resonance (EPR). The purpose of this work was to solve the problem of asymmetric EPR absorption spectra in spectral processing. A hybrid function of Gaussian and Lorentzian lineshapes was used to perform spectral line-fitting to successfully separate the two kinds of nitroxyl radicals. This approach can process the asymmetric EPR absorption spectra of the nitroxyl radicals being measured, and can suppress image artifacts due to spectral asymmetry. With this improved visualization method and a 750-MHz continuous-wave EPR imager, a temporal change in the distributions of a two-phase paraffin oil and water/glycerin solution system was visualized using lipophilic and hydrophilic nitroxyl radicals, i.e., 2-(14-carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxy (16-DOXYL stearic acid) and 4-hydroxyl-2,2,6,6-tetramethylpiperidine-d17-1-(15)N-1-oxyl (TEMPOL-d17-(15)N). The results of the two-phase separation experiment verified that reasonable artifact suppression could be achieved by the present method that deals with asymmetric absorption spectra in the EPR imaging of (14)N- and (15)N-labeled nitroxyl radicals.
authors.affiliation: Division of Bioengineering and Bioinformatics, Graduate School of Information Science and Technology, Hokkaido University, North 14, West 9, Kita-ku, Sapporo 060-0814, Japan.
authors.forename: Wataru
authors.initials: W
authors.lastname: Takahashi
authors.affiliation: Division of Bioengineering and Bioinformatics, Graduate School of Information Science and Technology, Hokkaido University, North 14, West 9, Kita-ku, Sapporo 060-0814, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Miyake
authors.affiliation: Division of Bioengineering and Bioinformatics, Graduate School of Information Science and Technology, Hokkaido University, North 14, West 9, Kita-ku, Sapporo 060-0814, Japan. Electronic address: hhirata@ist.hokudai.ac.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hirata
keywords: EPR imaging; Image reconstruction; Nitroxyl radicals; Spectral fitting