title: Instantaneous signal loss simulation (InSiL): an improved algorithm for myocardial T₁ mapping using the MOLLI sequence.
abstract: OBJECTIVE
  To propose a T1 mapping algorithm for the modified Look-Locker inversion-recovery (MOLLI) sequence that can improve T1 estimation accuracy.
  
  
  METHODS
  The modified T1 mapping algorithm (InSiL) is based on the simulation of MOLLI signal evolution and simulates the longitudinal magnetization signal perturbation by each single-shot image acquisition in MOLLI as an instantaneous signal loss. InSiL was evaluated against original MOLLI using Bloch simulations, phantom studies, and in 15 healthy volunteers at 1.5T.
  
  
  RESULTS
  In phantom studies, the maximum absolute error by InSiL is less than 2%, while that by MOLLI is more than 20% for T1 values from 221 msec to 1539 msec. The benefit of InSiL is greatest at heart rate (HR) >80 bpm and T1 >1000 msec, and InSiL reduced MOLLI T1 error from 14.9 ± 4.5% to 0.4 ± 0.3%. Average InSiL-derived native myocardial T1 values at 1.5T in healthy volunteers were significantly higher than MOLLI-derived values by 236.9 ± 11.7 msec (1160.3 ± 25.1 msec vs. 923.4 ± 22.3 msec, P < 0.001) at an average HR of 65.1 ± 14.7 bpm.
  
  
  CONCLUSIONS
  The proposed InSiL approach yields better T1 mapping accuracy than MOLLI, and is less sensitive to HR variation in tissues with longer T1 values.
authors.affiliation: Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles, California, USA.
authors.forename: Jiaxin
authors.initials: J
authors.lastname: Shao
authors.forename: Kim-Lien
authors.initials: KL
authors.lastname: Nguyen
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Natsuaki
authors.forename: Bruce
authors.initials: B
authors.lastname: Spottiswoode
authors.forename: Peng
authors.initials: P
authors.lastname: Hu
mesh_terms: D000328:Adult; D000465:Algorithms; D005260:Female; D006321:Heart / Q000033:anatomy & histology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D019047:Phantoms, Imaging; D015203:Reproducibility of Results
keywords: MR relaxometry; T1 mapping; myocardial scar imaging; quantitative MRI