title: T1 measurements in the human myocardium: the effects of magnetization transfer on the SASHA and MOLLI sequences.
abstract: OBJECTIVE
  Quantitative mapping of the native T1 of the heart using the modified look-locker inversion recovery (MOLLI) technique provides high quality diagnostic information without requiring contrast agents. Previous work has considered the effects of T2 relaxation on MOLLI T1 measurements, finding that the T1 measured by MOLLI is biased, and that Saturation-recovery single-Shot Acquisition generates a more precise T1. However, despite detailed experiments and simulation the exact relaxation times observed in vivo remain unexplained, but might be due to magnetization transfer (MT).
  
  
  METHODS
  We used an MT simulation based on the Bloch-McConnell equations to evaluate the most common MOLLI and saturation-recovery single-shot acquisition sequence variants.
  
  
  RESULTS
  For myocardial tissue we find that the T1 measured by saturation-recovery single-shot acquisition is insensitive to MT and T2, whereas MT reduces the T1 measured by MOLLI (>10%) in addition to the effects due to T2 relaxation.
  
  
  CONCLUSIONS
  The consequences of this T1 underestimation by MOLLI are relevant. Increases in the actual T1 and T2 and decreases in MT will all result in an increase in T1 measured by MOLLI. Myocardial infarction demonstrates increased native T1 and T2 and decreased MT, indicating that these biases enhance the sensitivity of MOLLI to detect this and possibly other cardiovascular disease states.
authors.affiliation: Division of Cardiovascular Medicine, Radcliffe Department of Medicine, Oxford Centre for Clinical Magnetic Resonance Research, University of Oxford, John Radcliffe Hospital, Oxford, UK.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Robson
authors.forename: Stefan K
authors.initials: SK
authors.lastname: Piechnik
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Tunnicliffe
authors.forename: Stefan
authors.initials: S
authors.lastname: Neubauer
mesh_terms: D006321:Heart / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008962:Models, Theoretical; D018482:Muscle, Skeletal / Q000502:physiology
keywords: T1 mapping; cardiac MRI; magnetization transfer; tissue characterization