title: In vivo field-cycling relaxometry using an insert coil for magnetic field offset.
abstract: OBJECTIVE
  The T(1) of tissue has a strong dependence on the measurement magnetic field strength. T(1) -dispersion could be a useful contrast parameter, but is unavailable to clinical MR systems which operate at fixed magnetic field strength. The purpose of this work was to implement a removable insert magnet coil for field-cycling T(1) -dispersion measurements on a vertical-field MRI scanner, by offsetting the static field over a volume of interest.
  
  
  METHODS
  An insert magnet coil was constructed for use with a whole-body sized 59 milli-Tesla (mT) vertical-field, permanent-magnet based imager. The coil has diameter 38 cm and thickness 6.1 cm and a homogeneous region (± 5%) of 5 cm DSV, offset by 5 cm from the coil surface. Surface radiofrequency (RF) coils were also constructed.
  
  
  RESULTS
  The insert coil was used in conjunction with a surface RF coil and a volume-localized inversion-recovery pulse sequence to plot T(1) -dispersion in a human volunteer's forearm over a range of field strengths from 1 mT to 70 mT.
  
  
  CONCLUSIONS
  T(1) -dispersion measurements were demonstrated on a fixed-field MRI scanner, using an insert coil. This demonstrates the feasibility of relaxation dispersion measurements on an otherwise conventional MR imager, facilitating the exploitation of T(1) -dispersion contrast for enhanced diagnosis.
authors.affiliation: Aberdeen Biomedical Imaging Centre, University of Aberdeen, Aberdeen, Scotland, United Kingdom.
authors.forename: Kerrin J
authors.initials: KJ
authors.lastname: Pine
authors.forename: Fred
authors.initials: F
authors.lastname: Goldie
authors.forename: David J
authors.initials: DJ
authors.lastname: Lurie
mesh_terms: D004867:Equipment Design; D005542:Forearm / Q000033:anatomy & histology; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation*; D060526:Magnetic Fields; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D011846:Radio Waves
keywords: T1 relaxometry; field-cycling; insert coil; nuclear magnetic resonance