title: Comparison of breath-hold, respiratory navigated and free-breathing MR elastography of the liver.
abstract: Hepatic magnetic resonance elastography (MRE) is currently a breath-hold imaging technique. Patients with chronic liver disease can have comorbidities that limit their ability to breath-hold (BH) for the required acquisition time. Our aim was to evaluate whether stiffness measurements obtained from a navigator-triggered MRE acquisition are comparable to standard expiratory breath-hold, inspiratory breath-hold or free-breathing in healthy participants.
  
  
  
  Twelve healthy participants were imaged using the four methods on a clinical 1.5T MR system equipped with a product MRE system. Mean liver stiffness, and measurable area of stiffness (with a confidence threshold >95%) were compared between sequences using the concordance correlation coefficient. Repeatability of each sequence between two acquisitions was also assessed.
  
  
  
  The standard BH expiratory technique had high concordance with the navigated technique (r=0.716), and low concordance with the BH inspiration (r=0.165) and free-breathing (r=0.105) techniques. The navigator-triggered technique showed no statistical difference in measurable area of liver or in repeatability compared with the standard expiratory acquisition (p=0.997 and p=0.407 respectively). The free-breathing technique produced less measurable liver area and was less repeatable than the alternative techniques. The increase in acquisition time for navigator techniques was 3min 6s compared to standard expiratory breath-hold.
  
  
  
  Navigator-based hepatic MRE measurements are comparable to the reference standard expiratory breath-hold acquisition in healthy participants.
authors.affiliation: Dept of Radiology, University of Cambridge and Addenbrooke's Hospital, Hills Rd, CB20QQ, England, United Kingdom. Electronic address: iangmurphy@gmail.com.
authors.forename: Ian Gavin
authors.initials: IG
authors.lastname: Murphy
authors.affiliation: Dept of Radiology, University of Cambridge and Addenbrooke's Hospital, Hills Rd, CB20QQ, England, United Kingdom.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Graves
authors.affiliation: GE Healthcare, Amersham, HP7 9NA, United Kingdom.
authors.forename: Scott
authors.initials: S
authors.lastname: Reid
authors.affiliation: Dept of Radiology, University of Cambridge and Addenbrooke's Hospital, Hills Rd, CB20QQ, England, United Kingdom.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Patterson
authors.affiliation: Dept of Radiology, University of Cambridge and Addenbrooke's Hospital, Hills Rd, CB20QQ, England, United Kingdom.
authors.forename: Ilse
authors.initials: I
authors.lastname: Patterson
authors.affiliation: Dept of Radiology, University of Cambridge and Addenbrooke's Hospital, Hills Rd, CB20QQ, England, United Kingdom.
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Priest
authors.affiliation: Dept of Radiology, University of Cambridge and Addenbrooke's Hospital, Hills Rd, CB20QQ, England, United Kingdom.
authors.forename: David J
authors.initials: DJ
authors.lastname: Lomas
mesh_terms: D000328:Adult; D062485:Breath Holding; D015331:Cohort Studies; D054459:Elasticity Imaging Techniques; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008099:Liver / Q000000981:diagnostic imaging*; D008107:Liver Diseases; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012015:Reference Standards; D015203:Reproducibility of Results; D012119:Respiration; D055815:Young Adult
keywords: Elastography; Free-breathing; Liver stiffness; Magnetic resonance; Navigator- triggered