title: Inversion group (IG) fitting: A new T1 mapping method for modified look-locker inversion recovery (MOLLI) that allows arbitrary inversion groupings and rest periods (including no rest period).
abstract: The Modified Look-Locker Inversion Recovery (MOLLI) technique is used for T1 mapping in the heart. However, a drawback of this technique is that it requires lengthy rest periods in between inversion groupings to allow for complete magnetization recovery. In this work, a new MOLLI fitting algorithm (inversion group [IG] fitting) is presented that allows for arbitrary combinations of inversion groupings and rest periods (including no rest period).
  
  
  
  Conventional MOLLI algorithms use a three parameter fitting model. In IG fitting, the number of parameters is two plus the number of inversion groupings. This increased number of parameters permits any inversion grouping/rest period combination. Validation was performed through simulation, phantom, and in vivo experiments.
  
  
  
  IG fitting provided T1 values with less than 1% discrepancy across a range of inversion grouping/rest period combinations. By comparison, conventional three parameter fits exhibited up to 30% discrepancy for some combinations. The one drawback with IG fitting was a loss of precision-approximately 30% worse than the three parameter fits.
  
  
  
  IG fitting permits arbitrary inversion grouping/rest period combinations (including no rest period). The cost of the algorithm is a loss of precision relative to conventional three parameter fits. Magn Reson Med 75:2332-2340, 2016. © 2015 Wiley Periodicals, Inc.
authors.affiliation: Joint Department of Medical Imaging, University Health Network, University of Toronto, Toronto, Ontario, Canada.|Department of Medical Imaging, University of Toronto, Toronto, Ontario.
authors.forename: Marshall S
authors.initials: MS
authors.lastname: Sussman
authors.affiliation: Joint Department of Medical Imaging, University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Issac Y
authors.initials: IY
authors.lastname: Yang
authors.affiliation: Joint Department of Medical Imaging, University Health Network, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Kai-Ho
authors.initials: KH
authors.lastname: Fok
authors.affiliation: Joint Department of Medical Imaging, University Health Network, University of Toronto, Toronto, Ontario, Canada.|Department of Medical Imaging, University of Toronto, Toronto, Ontario.
authors.forename: Bernd J
authors.initials: BJ
authors.lastname: Wintersperger
mesh_terms: D000465:Algorithms; D057791:Cardiac Imaging Techniques / Q000379:methods*; D003198:Computer Simulation; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results
keywords: Look-Locker; MOLLI; MRI; T1; cardiac; transient SSFP