title: Long-term reproducibility of phantom signal intensities in nonuniformity corrected STIR-MRI examinations of skeletal muscle.
abstract: OBJECTIVE
  Nerve regeneration could be monitored by comparing MRI image intensities in time, as denervated muscles display increased signal intensity in STIR sequences. In this study long-term reproducibility of STIR image intensity was assessed under clinical conditions and the required image intensity nonuniformity correction was improved by using phantom scans obtained at multiple positions.
  
  
  METHODS
  Three-dimensional image intensity nonuniformity was investigated in phantom scans. Next, over a three-year period, 190 clinical STIR hand scans were obtained using a standardized acquisition protocol, and corrected for intensity nonuniformity by using the results of phantom scanning. The results of correction with 1, 3, and 11 phantom scans were compared. The image intensities in calibration tubes close to the hands were measured every time to determine the reproducibility of our method.
  
  
  RESULTS
  With calibration, the reproducibility of STIR image intensity improved from 7.8 to 6.4%. Image intensity nonuniformity correction with 11 phantom scans gave significantly better results than correction with 1 or 3 scans.
  
  
  CONCLUSIONS
  The image intensities in clinical STIR images acquired at different times can be compared directly, provided that the acquisition protocol is standardized and that nonuniformity correction is applied. Nonuniformity correction is preferably based on multiple phantom scans.
authors.affiliation: Department of Radiology, University Medical Center Groningen, Hanzeplein 1, 9700 RB Groningen, The Netherlands. a.r.viddeleer@rad.umcg.nl
authors.forename: Alain R
authors.initials: AR
authors.lastname: Viddeleer
authors.forename: Paul E
authors.initials: PE
authors.lastname: Sijens
authors.forename: Peter M A
authors.initials: PM
authors.lastname: van Ooijen
authors.forename: Paul D L
authors.initials: PD
authors.lastname: Kuypers
authors.forename: Steven E R
authors.initials: SE
authors.lastname: Hovius
authors.forename: Matthijs
authors.initials: M
authors.lastname: Oudkerk
mesh_terms: D000465:Algorithms; D002138:Calibration; D004867:Equipment Design; D006225:Hand / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods*; D018482:Muscle, Skeletal / Q000378:metabolism; D009416:Nerve Regeneration; D010363:Pattern Recognition, Automated; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D013997:Time Factors