title: A direct comparison of signal behavior between 4.0 and 1.5 T: a phantom study.
abstract: BACKGROUND
  Higher magnetic fields (>or=3 T) afford higher spatial and/or temporal resolution in MR imaging with contrast agents, however, studies containing direct comparisons of signal intensity among different magnetic fields are substantially sparse. Our aim was to quantify the differences in terms of signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) between higher and lower (<or=1.5 T) magnetic fields and to clarify the benefit of higher magnetic fields.
  
  
  METHODS
  The same sets of phantom experiments were conducted at both 4 and 1.5 T on whole-body MR scanners with head coils. Phantoms included different concentrations of Gd chelate water solution. A standard contrast-enhanced MR angiographic sequence with the same imaging parameters was utilized to confirm changes in signal intensities. Furthermore, the results were compared with a computer simulation.
  
  
  RESULTS
  Peak SNRs at 4 T increased at least 2.21 times higher compared with those at 1.5 T. Moreover, peak CNRs at 4 T increased at least 1.59 times higher compared with those at 1.5 T in the range of Gd concentration expected during clinical use.
  
  
  CONCLUSIONS
  Higher magnetic fields benefit CNRs as well as SNRs. These advantages may lead to a high resolution imaging and reduction of scan time.
authors.affiliation: Department of Radiology, University of Pennsylvania Medical Center, 3600 Market Street, Suite 370, Philadelphia, PA 19104-2649, USA.
authors.forename: Hidemasa
authors.initials: H
authors.lastname: Uematsu
authors.forename: Lawrence
authors.initials: L
authors.lastname: Dougherty
authors.forename: Masaya
authors.initials: M
authors.lastname: Takahashi
authors.forename: Norman S
authors.initials: NS
authors.lastname: Butler
authors.forename: Hee Kwon
authors.initials: HK
authors.lastname: Song
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Ohno
authors.forename: Warren B
authors.initials: WB
authors.lastname: Gefter
authors.forename: Mitchell D
authors.initials: MD
authors.lastname: Schnall
authors.forename: Hiroto
authors.initials: H
authors.lastname: Hatabu
mesh_terms: D003198:Computer Simulation; D003287:Contrast Media; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008280:Magnetics; D019047:Phantoms, Imaging; D012815:Signal Processing, Computer-Assisted
chemical_list: D003287:Contrast Media