title: Frequency bandwidth extension by use of multiple Zeeman field offsets for electron spin-echo EPR oxygen imaging of large objects.
abstract: OBJECTIVE
  Electron spin-echo (ESE) oxygen imaging is a new and evolving electron paramagnetic resonance (EPR) imaging (EPRI) modality that is useful for physiological in vivo applications, such as EPR oxygen imaging (EPROI), with potential application to imaging of multicentimeter objects as large as human tumors. A present limitation on the size of the object to be imaged at a given resolution is the frequency bandwidth of the system, since the location is encoded as a frequency offset in ESE imaging. The authors' aim in this study was to demonstrate the object size advantage of the multioffset bandwidth extension technique.
  
  
  METHODS
  The multiple-stepped Zeeman field offset (or simply multi-B) technique was used for imaging of an 8.5-cm-long phantom containing a narrow single line triaryl methyl compound (trityl) solution at the 250 MHz imaging frequency. The image is compared to a standard single-field ESE image of the same phantom.
  
  
  RESULTS
  For the phantom used in this study, transverse relaxation (T(2e)) electron spin-echo (ESE) images from multi-B acquisition are more uniform, contain less prominent artifacts, and have a better signal to noise ratio (SNR) compared to single-field T(2e) images.
  
  
  CONCLUSIONS
  The multi-B method is suitable for imaging of samples whose physical size restricts the applicability of the conventional single-field ESE imaging technique.
authors.affiliation: Department of Radiation and Cellular Oncology, Center for EPR Imaging In Vivo Physiology, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Payam
authors.initials: P
authors.lastname: Seifi
authors.forename: Boris
authors.initials: B
authors.lastname: Epel
authors.forename: Subramanian V
authors.initials: SV
authors.lastname: Sundramoorthy
authors.forename: Colin
authors.initials: C
authors.lastname: Mailer
authors.forename: Howard J
authors.initials: HJ
authors.lastname: Halpern
mesh_terms: D004578:Electron Spin Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D004583:Electrons; D007091:Image Processing, Computer-Assisted; D057054:Molecular Imaging / Q000295:instrumentation / Q000379:methods*; D010100:Oxygen / Q000378:metabolism*; D019047:Phantoms, Imaging
chemical_list: D010100:Oxygen