title: Free-breathing MOLLI: application to myocardial T(1) mapping.
abstract: OBJECTIVE
  Of the myocardial T(1) mapping techniques, the modified Look-Locker inversion recovery (MOLLI) sequence is accurate and highly reproducible. The MOLLI sequence requires patients to hold their breath for 17 heartbeats during the scanning process to minimize respiratory motion-related artifacts. However, some patients are unable to hold their breath because of illness or limited breath-hold capacity. This study, therefore, aimed to develop a robust myocardial T(1) mapping method based on the MOLLI sequence for patients unable to perform voluntary breath-holds.
  
  
  METHODS
  This study presents a free-breathing MOLLI (FB-MOLLI) sequence and an optimized reconstruction method to allow myocardial T(1) mapping in vivo without breath-hold. Nine healthy volunteers participated in this study after providing institutionally approved consent. The FB-MOLLI sequence acquires 20 images within 29 heartbeats. The reconstruction program employs a two-step automatic image registration technique and an image selection method inspired by the self-gating cardiac imaging method.
  
  
  RESULTS
  Results indicate that the proposed reconstruction method increases the accuracy and reproducibility of free-breathing T(1) measurements significantly (p < 0.001).
  
  
  CONCLUSIONS
  The FB-MOLLI method provides a robust tool for clinical application in free-breathing myocardial T(1) mapping, and could greatly facilitate acquisition procedures during routine examinations.
authors.affiliation: Department of Electrical Engineering, National Taiwan University of Science and Technology, Taiwan, Republic of China.
authors.forename: Jyun-Ming
authors.initials: JM
authors.lastname: Tsai
authors.forename: Teng-Yi
authors.initials: TY
authors.lastname: Huang
authors.forename: Yu-Shen
authors.initials: YS
authors.lastname: Tseng
authors.forename: Yi-Ru
authors.initials: YR
authors.lastname: Lin
mesh_terms: D000465:Algorithms; D055424:Cardiac-Gated Imaging Techniques / Q000379:methods*; D006321:Heart / Q000033:anatomy & histology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010363:Pattern Recognition, Automated / Q000379:methods*; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D055425:Respiratory-Gated Imaging Techniques / Q000379:methods*; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D055815:Young Adult